Everything you need to know about vitamin D - yes, everything.
- Michelle Adams
- Mar 23
- 35 min read
You can listen to the video version of this article here.
Have you ever noticed how a lot of people seem to be deficient in vitamin D? If you are fortunate enough to have access to healthcare, you have probably gotten a test of your vitamin D level done at some point and noticed that you were deficient. The fact that vitamin D deficiency is so widespread seems absurd on the surface; How is it that SO many of us are deficient in a vitamin that you can get just from going outside? Is it because we are spending too much time indoors, scrolling on our phones and binge-watching Netflix? Is it because we are not eating enough foods that are rich in vitamin D? What if the problem lies with the actual test, and we are all being scammed while the people selling vitamin D supplements are making hundreds of millions of dollars a year off of our ignorance?
And who is this guy, and how is he largely responsible for this whole vitamin D craze? (Image source: drmichaelholick.org)
Today I will be answering all of those questions, and more! But first, let's start with a little background:
What is vitamin D, and why is it important?
Vitamin D is known as the “sunshine vitamin,” because it is made as a result of exposure to the sun. Here is how it works – the sun emits different types of ultraviolet (UV) radiation – it is the UVB radiation, which travels over 93 million miles from the sun to the earth and penetrates your skin, that gets this process started. This process can be a bit confusing because of how similar the names for all of the different forms of vitamin D are, but just stick with me. The UVB converts the provitamin D (7-dehydrocholesterol) in your skin into previtamin D. The previtamin D then morphs into vitamin D3 via a process known as isomerization. It travels down the blood stream to the liver, where it goes through yet another conversion to become 25-hydroxyvitamin D. But, that is still not its final form. The last conversion, where vitamin D becomes its active form, happens primarily in our kidneys – that’s where it becomes 1,25-dihydroxyvitamin D. You can also get vitamin D from your diet. Some of the best sources are fatty fish like salmon and that delicious-tasting cod liver oil that your mom used to make you swallow a spoon of from time to time when you were a child.
Vitamin D is mainly important for the health of your bones, as it is needed for calcium absorption. It also plays a role in the regulation of cell growth, and in the production of renin, a hormone that is key for blood pressure regulation. When you don’t get enough vitamin D as a child, you are more likely to develop rickets, a condition where a person's bones are weak and deformed. For adults, you are more likely to develop osteomalacia, wherein the bones are weak and can easily fracture or break. Vitamin D deficiency is also linked to chronic muscle and bone pain and a higher risk of falls. Vitamin D has also been linked to cancer, diabetes, heart disease, and other conditions – but those associations are more nuanced, so I will save them for later on in this article.
These children were diagnosed with Rickets. (Image source: Thacher 2003)
As you can see, vitamin D plays numerous critical roles in the body; a deficiency, especially during childhood, produces noticeable symptoms and can be life-altering. Nevertheless, people are being diagnosed with low vitamin D left and right. This begs the question - given how important this nutrient is, why are so many people still low in it? A rule of thumb to understand why seemingly illogical things happen in society is to follow the money. Profits are not inherently bad, but they do oftentimes help to shed light on things. Vitamin D testing and supplements are huge markets, so we know of at least two groups that are benefiting from vitamin D deficiency being such a common diagnosis.
Who is making money off of all of this vitamin D testing?
More people are taking vitamin D tests than ever before, and in tandem with that, more people are being diagnosed with vitamin D deficiency than in previous years as well. All of this is happening despite the fact that population-wide vitamin D testing is actually not recommended by the US Preventative Services Task Force, the National Academy of Medicine, nor the Endocrine Society. These health authorities have basically said that it’s a wasteful medical practice.
Part of what set off the modern wave of testing is the work of the person whose photo you saw up top – Dr. Michael Holick, a medical doctor and biochemistry PhD at Boston University. Dr. Holick is THE foremost expert in vitamin D research. He was the first person to identify the form of vitamin D that labs measure when you get a vitamin D test ordered.
He was also the first to identify and synthesize the active form of vitamin D that is used in various medical treatments, which is pretty cool. (Image source: drmichaelholick.org)
In his almost 40 years of work, he has helped over 25,000 patients, many of whom had issues related to vitamin D, authored over 600 research papers, and his work been cited in other research papers over 150,000 times. It’s fair to say that he knows a lot about vitamin D. Where things get saucy though, is when we look at his work with the Endocrine Society.
The Endocrine Society (henceforth referred to as the ES) is an organization whose recommendations shape medical guidelines that are implemented by hospitals and testing laboratories all across the nation, including the recommendations for vitamin D. With Dr. Holick’s help, they come up with the recommendation that most people need to raise their vitamin D levels to 30 ng/mL (75 nmol/L). All of that sounds fine and dandy, until you look at the fact that this vitamin D threshold is much higher than the one that a different, highly reputable organization recommends. In 2010, the National Academy of Medicine (NAM), formerly known as the Institute of Medicine (IOM), published their recommendations, which are that vitamin D levels between 12-16 ng/mL are sufficient for maintaining healthy bones, with there being no benefit past 20 ng/mL (50 nmol/L).
Just a note - the dates may look a bit off here, because the recommendations were published in November of 2010, as you can see from the first paragraph of this article, but the report is from 2011.
The fact that these two major medical organizations contradicted each other is a huge deal, because the ES is the one that medical providers generally look to for recommendations. Even though the NAM said that people could be fine with lower levels of vitamin D, the medical community pretty much went with the higher cutoff recommended by the ES. The problem though, is that a higher threshold means that way more people are considered to be vitamin D deficient than would be the case if they had went with the NAM guideline. More “deficient” people means more testing, and more supplementing. According to the NAM, having this higher cut off is not justifiable. They even published a rebuttal in 2012, where they pointed out weak spots in the ES recommendations – one study that the ES used to make their recommendations had just 34 people. There is apparently also some evidence of the ES cherry-picking data and ignoring a study of 300 people which found that going past just 8 ng/mL of vitamin D provided no benefit for calcium absorption. Another issue that they pointed out is the use of observational studies to make clinical recommendations – higher vitamin D levels are correlated with some positive health outcomes, but, as I’ll discuss later, that doesn’t tell us anything about the good or even bad effects of trying to raise people’s vitamin D levels higher and higher.
Dr. Holick has come under fire for making money off of this vitamin D craze, which is the subject of this article that was published in the New York Times. I decided to check for myself, using the Medicare Open Payments Database. This is a free website that lets you see what types of funding medical providers are getting from drug and medical device companies. The database covers payments made between January 2016 and December 2022. I have to say – the New York Times article made this guy out to be a villain when that doesn’t seem to be the case. When I looked at the payments for 2022, I was underwhelmed – Dr. Holick received a mere $3,320. In 2016 he did make a lot of money, more than average – but it wasn’t an evil villain amount of money. The real money is being spilled from your pockets, and mine, into Medicare.
According to the Centers for Medicare and Medicaid, Vitamin D testing is the 5th most common lab test for older adults. In 2015 alone, $337 million Medicare dollars went to vitamin D testing, which in up to 77% of cases was not even necessary since the patients did not present with any risk for vitamin D deficiency. This is a 1.5 billion dollar market, and it is expected to continue to expand.
But, could it actually be a good thing that we are paying so much attention to this one vitamin?
Are we ACTUALLY all deficient in vitamin D?
Everyone and their grandmother are getting vitamin D tests done, but, is vitamin D deficiency really that big of a deal? It turns out that the answer is: yes. This paper is from a study on about 4500 adults that served as a representative sample of the whole population of the United States. Vitamin D deficiency was defined using the lower cutoff point established by the NAM - 20 ng/mL. Overall, about 42% of the US adult population was found to be deficient in vitamin D. When you break things down by race, the numbers get even worse. 82% of Black people were found to be deficient, while almost 70% of people who identified as Hispanic were found to be deficient. It’s possible that some fraction of these people are actually just fine – remember, the NAM reported that for many people, 12-16 ng/mL may be okay. Still, these numbers are egregious!
That paper is from 2011, though. Let’s take a look at some more recent data from 2022. This paper analyzed trends in vitamin D levels in a representative sample of over 71,000 Americans between 2001 and 2018. This time, the results were much more hopeful. Overall, around 25% of the population was classified as vitamin D deficient. Looking at the most susceptible races again, 60% of Black people and 31-38% of Hispanics were deficient. The prevalence of vitamin D deficiency is actually going down, I’m happy to report.
Over HALF of us highly-melanated people are still deficient though, which may or may not be a major problem. More on that later.
Potential explanations for the improvement in vitamin D status
There are at least four reasons why vitamin D deficiency is becoming less common in the US:
More people are getting their vitamin D levels tested, so we are catching more cases of vitamin D deficiency, which gives us the chance to correct the deficiency. You can’t fix a problem if you don’t know that it exists.
Healthcare providers are recommending that people taking higher doses of vitamin D.
People are spending more money (see here, and here) on vitamin D supplements than before.
And lastly,
We have found increasingly creative ways to add vitamin D to the food supply. For example, in the summer of 2023, General Mills announced that they would be doubling the amount of vitamin D in their popular breakfast cereals, including Lucky Charms, Cinnamon Toast Crunch, and Cheerios. These cereals still have plenty of sugar though, but, I digress.
As a nation, we have come really far in terms of improving our vitamin D levels. However, has that translated to us being healthier as a nation?
Since we have been taking all of this vitamin D, have we actually gotten healthier?
Like I said earlier, vitamin D is primarily important for the health of our bones. For that reason, I’m going to answer this question first by looking at data on osteoporosis, then bone mineral density, and finally, bone fractures. Don't worry, data on other health conditions will be addressed further down.
Osteoporosis: Based on national data comparing trends in osteoporosis between 2007-2018, the answer is…no. For people aged 50 and over, the prevalence of osteoporosis has actually been trending up, mainly in women, where it went up from 14.0% to 19.6%.
Bone mineral density: Looking at the same data, we can see that there hasn’t been any improvement in bone mineral density either. The prevalence of low bone mass was 43.0% between 2007-2008, and 43.1% ten years later for the 2017-2018 time period.
Bone fractures: According to this paper, which includes an analysis of fracture data for the United States for the past 20 years (1999 -2020) in older adults ages 50 years plus, the fraction of people with bone fractures has not gone down either. In this span of time, millions of Americans had hip fractures, wrist fractures, and vertebral fractures, i.e. fractures of the spine. The prevalence of wrist fractures actually went up significantly, from 8.7% to 12.8%. The prevalence of vertebral fractures went up too, from 2.2% to 4.6%. The frequency of hip fractures pretty much stayed the same. Other studies show that some types of fractures are becoming less common, fortunately. In this study of close to over 930,000 people, also aged 50 years and above, who had commercial insurance or Medicare Advantage between 2007 and 2017, researchers found that fracture risk trended down for the first several years, stabilized, then started to trend up – primarily for women aged 65 years or older. For many types of fracture, the rates were stable or even declined over the study period. You can really see that decline with hip and ankle fractures. Spine fractures accounted for much of the observed increase in fracture rates. The decline in hip fractures was also detected in this study.
The main markers of bone health that are associated with vitamin D on a whole don’t seem to have improved all that much. Still, it is possible that it may take a couple more decades before we can really tell if vitamin D supplements are making a marked difference for bone health on national level. Anyway, vitamin D is important for bone health, but that’s not the only thing that it’s essential for. Taking a vitamin D supplement could help you out in other ways.
Is taking a vitamin D supplement still a good idea?
Certain populations actually are recommended to take vitamin D supplements.
One of them is these cuties.
The American Academy of Pediatrics recommends 400 IU per day of vitamin D for newborns who are partially or exclusively breast fed. Infants and children who drink less that 32 oz of formula or milk that has been fortified with vitamin D are recommended to supplement the same amount of vitamin D as well.
I’ll quickly go over what the data have to say about the following conditions:
Prediabetes/Diabetes
Cancer
Cardiovascular disease
Bone health
Depression
Multiple sclerosis
COVID-19
Prediabetes/Diabetes
Vitamin D can help to keep blood sugar levels within the healthy range by stimulating the release of insulin from the pancreas. Insulin is a hormone that helps glucose to get into our cells to be used for energy. In this study where researchers combined data from multiple randomized controlled trials, it was found that taking vitamin D supplements may actually help with blood sugar management. Several other studies (like this one, this one, this one, and this one) provide supporting evidence. These studies were carried out across the US, Canada, Europe, and New Zealand. Participants were mainly older adults (around 60-70 years of age) and were majority White. The fact that these studies included people of mostly European descent is important because – spoiler – the way that our bodies metabolize vitamin D actually differs from one race to the next.
More than one of these clinical trials used doses of 2000 IU per day, which is the typical dose that you would see if you went to your nearest grocery store to pick up some vitamin D softgels. These studies lasted from as little as 2 years up to around 5 years. The largest study, VITAL, included over 25,000 people, a pretty substantial sample size. For people with prediabetes, vitamin D supplements actually helped to slow down disease progression by about 10%. That’s right, vitamin D supplements helped people with prediabetes to reduce their chances of developing full blown type 2 diabetes. But, we have to be careful with these results – this outcome was not true for everyone. It was mainly the people who had a BMI under 30 (i.e. who were not obese), who were already severely deficient in vitamin D, and who were able to bring their serum levels up to 100 nmol/L (40 ng/mL).
There are also several older studies which used very high doses of vitamin D that show no benefit for blood sugar management. One of these studies had a relatively small population – just 54 people completed the study – and the dose of vitamin D was sky-high – a 100,000 IU one time dose, follower by 4000 IU per day for 16 weeks. Another study, a meta-analysis of 35 trials with over 43,000 participants total, covered a very wide range of vitamin D doses, many of which were also much higher than what you would find in your typical drug store; dosages ranged from a 300,000 IU single dose, to 140,000 IU per month, to 60,000 IU per week, down to a more typical dose of 2000 IU per day. The last study also included very high doses, 20,000 IU per week for 5 years. Perhaps we can say that low or moderate doses of vitamin D are superior to very high doses for protecting against the progression of prediabetes to diabetes. The Recommended Dietary Allowance (RDA) for vitamin D for adults is just 600-800 IU per day.
The fact that a pill could potentially stave off a chronic disease that affects over 38 million Americans and costs the country over 400 billion dollars each year is great. But, this outcome is not all sunshine and rainbows for everyone. Do you remember me saying earlier that most of the people in the studies were White? Well, here is why I highlighted that fact: This potential benefit of vitamin D mainly applies to people who are White. If you have a bit more melanin in your skin, vitamin D supplementation may not help you. In this paper, which was based on an observational study of a representative sample people who identified as White, Black, or Mexican, it was reported that higher levels of vitamin D were associated with better blood sugar levels for Whites and Mexicans, but not for Blacks. A later study published in 2016 using updated national data found the same thing – higher vitamin D levels were not correlated with less diabetes in Black people.
Higher vitamin D levels are correlated with lower diabetes risk in Whites and Mexicans, but not Blacks. This is an example of why representation in clinical trials is so important!
Scientists aren’t entirely sure why there is a difference between races, but it has been suggested that Black people may be less sensitive to the effects of vitamin D. It has also been suggested that because Black people tend to have higher levels of parathyroid hormone (PTH) – which is correlated with a higher prevalence of diabetes and insulin resistance – they may simply be more at risk.
I would like to add a disclaimer here as well – if you have type 2 diabetes, and you happen to not be Black, please do not take this to mean that you can just start taking vitamin D and forget about all of the other things that factor into maintaining a healthy blood sugar! Your overall lifestyle still matters, i.e. what you eat, how often you exercise, what your sleep pattern looks like, and so forth. If your medical provider has recommended that you take certain medications to keep your blood sugar in check, you should still take them. Remember, I’m just a stranger online that talks about research. Only you and your care team know what’s best for you.
Also, this section on diabetes wasn't quick, I know, but there was a lot of data to cover! The other sections will be shorter, I promise.
Cancer
Animal studies have shown that vitamin D can hinder the growth of tumors by promoting apoptosis (programmed cell death), suppressing inflammation, and stopping tumor cells from undergoing a process called angiogenesis, which is the formation of new blood vessels that bring blood to the tumor and keep it thriving. It may also stop tumors from metastasizing, or spreading to other organs in the body. Keep in mind that studies in animals give us insight into what may or may not work in humans, but they do not prove that these treatments will work in a living breathing human being. Now, let’s look at some data from clinical trials in humans.
Overall, the data does not support the notion that taking vitamin D supplements can reduce your risk of getting cancer (also see here, here, and here). This is underwhelming, but this isn’t the whole story; when you look at the effect of vitamin D supplementation on cancer mortality, i.e. dying from cancer, there does actually appear to be a significant positive effect! In a large systematic review of 18 randomized controlled trials with a combined total of over 50,000 participants, researchers found that an average dose of around 1200 IU of vitamin D per day for 6 years was protective against death from cancer. Serum levels of 110 nmol/L (44 ng/mL) were needed to see these beneficial effects, and it takes several years to see any effect. However, the authors caution that this outcome is likely an imperfect one because a large chunk of the participants in these studies dropped out. These studies (one and two) also show that vitamin D supplements may lower a person's chances of dying from cancer.
These results are exciting, but I also have to mention that higher vitamin D levels are not always better when it comes to the Big C. There are several specific types of cancer for which having higher vitamin D levels has been shown to be a risk factor:
Breast cancer – in one study, women who took over 600 IU of vitamin D per day had a 28% increased risk of invasive breast cancer.
Pancreatic cancer – in a study of male smokers, scientists found that those with a vitamin D level over 65.5 nmol/L (26.2 ng/mL) had a 3x greater risk of developing pancreatic cancer. In another study, a serum level of 100 nmol/L (40 ng/mL) or higher was linked to an increased risk of pancreatic cancer.
Prostate cancer – while the data is mixed, a meta-analysis of 21 studies found that high levels of vitamin D, somewhere around 75 nmol/L (30 ng/mL), were associated with 17% higher risk of prostate cancer.
Cardiovascular disease
Results from observational studies consistently point to low vitamin D being linked to poorer cardiovascular health. Heart-related outcomes that have been linked to low vitamin D include high blood pressure, stroke, and death from cardiovascular disease. However, an analysis of randomized controlled trials which combined included tens of thousands of participants and over 5 years of follow up found little to no effect of vitamin D on heart-related outcomes. Even for people with low vitamin D, it’s not clear (this study shows a benefit, while this study and this study do not) that taking a supplement will help to reduce the risk of heart disease.
Bone health
Now, let’s look at bone health. Vitamin D supplementation just by itself (see this study, too) does not seem to have any meaningful impact on fracture risk. However, when we combine vitamin D with calcium, that’s where the magic happens – several studies (see one, two, three, and four) have shown that this duo is associated with a lower risk of hip fractures and fractures in general. In this study, 400-800 IU of vitamin D per day along with 1000-1200mg per day of calcium reduced general fracture risk by 6% and hip fracture risk by 16% (both results were statistically significant). Be careful with taking too much calcium though, as this could increase your risk of kidney issues, including kidney stones. Despite these mostly positive results, several other large studies (see one, two, three, four, five, and six) have shown no benefit when it comes to reducing fracture risk.
In these studies, Vitamin D by itself had little to no benefit when it came to improving bone mineral density (BMD) – unless you already have a vitamin D deficiency, defined as under 30 nmol/L (12 ng/mL). In another study, those taking vitamin D lost 0.5% less BMD than the control group, a difference that was only significant for the femoral neck and hip. An increase in BMD in the lumbar spine was noted as significant for those with a vitamin D level below 30 nmol/L. This other study supports this – 1000 IU of vitamin D per day increased BMD only in those with a vitamin D level under 30 nmol/L.
Interestingly, these findings may not apply to people of African descent. In a study of 260 older Black American females where participants were followed for 3 years and their serum vitamin D was raised from around 55 nmol/L (sufficient according to the NAM, insufficient according to the ES) to >75 nmol/L (sufficient according to the NAM, and the ES), no differences were found between the group taking vitamin D and the group taking the placebo. It sort of makes sense when you consider that people of African descent when compared to people of European descent generally conserve calcium in the body more efficiently, have a higher bone mass and higher peak bone mass, and have half the risk of fractures due to osteoporosis (see the discussion of this same study). It is quite possible that Black people may not need to worry about raising their serum levels as high as other races to protect bone health. This is just one study though – more research is needed.
Depression
In a meta-analysis of 14 observational studies, an association was found between low vitamin D and depression. However, we have to remember that correlation does not imply causation. When we look at studies that can actually tell us about causation, randomized controlled trials, there is zero support for the notion that taking vitamin D can help with depression (see one, two, three, four, and five). These studies included doses ranging from 400IU per day to 40,000 IU per week, young and old adults, and ranged from 5 days to 5 years; we have plenty of data to show that vitamin D supplementation isn’t a justified treatment for depression.
Going outside to touch grass and get some sunshine is probably still a good idea if you are fighting depression, though.
Multiple sclerosis
Next up, we have multiple sclerosis (MS). MS is a type of autoimmune disease where the body attacks the protective covering around nerve cells, causing problems like muscle weakness, cognitive impairment, and in extreme cases, difficulty walking and speaking. The theory that vitamin D could play a role in MS stems at least in part from the fact that MS is more common in populations that live near the northern and southern poles. Since these people get less sunlight than people who live near the equator, it was speculated that lack of sun exposure might increase the risk of developing MS. There is correlational data that supports the link between low vitamin D and the risk of developing MS. In one study out of Finland, women with vitamin D levels less than 12 ng/mL (30 nmol/L) had a 43% greater risk of developing MS when compared to women with vitamin D levels of 20 ng/mL (50 nmol/L) or higher. Data from similar studies show that vitamin D levels greater than or equal to 75 nmol/L (30 ng/mL) were linked to an approximately 60% lower risk of MS.
While these results are hopeful, we have to interpret with with a grain of salt; these were not intervention studies where people took vitamin D or a placebo, and researchers could actually compare and see who developed MS and who didn’t. These were observational studies. We don’t have any intervention studies that show that taking vitamin D supplements can prevent MS.
What about if you already have MS though – can vitamin D help you to manage your symptoms? In a high-quality analysis of 12 trials that were designed to answer this question, the authors concluded that the trials were unfortunately of low quality, and that there was no indication that vitamin D supplements could help with MS symptoms or relapse.
COVID-19
While the COVID-19 pandemic was at its height, a lot of us were scrambling to figure out what to do to protect ourselves from this then-unknown virus. Vitamin D came into the spotlight as a nutrient that could protect against infection, and there is actually research that supports this claim. While having low vitamin D levels do not appear to be correlated with your chances of being infected with COVID-19, people with severe cases of COVID-19, where the individual was more likely to be hospitalized or die from the infection, were more likely to also be vitamin D deficient.
Summary of the data
To summarize the previous section, taking a vitamin D supplement may be beneficial for preventing diabetes and death from cancer, but not for developing cancer, cardiovascular disease, or depression. Data on bone fracture risk, bone mineral density, and multiple sclerosis are mixed. Being vitamin D deficient is associated with succumbing to COVID-19.
Why it is so difficult to come up with a single recommendation
Determining what the ideal level of vitamin D is for people is no easy task, because the ideal level of vitamin D varies A LOT depending on what disease or condition you are focusing on. Let’s take a closer look at this quandary.
A blood level of 5.5-12 ng/mL (13.75-30 nmol/L) is good for having a baby that is born at a healthy weight, but going past 30 ng/mL (75 nmol/L) may increase your risk of having a baby that is small for their age. In studies that showed that vitamin D could help reduce the risk of fractures in older adults though, blood levels of 40 ng/mL (100 nmol/L) were shown to be beneficial. Getting up to 40 ng/mL (100 nmol/L) also seemed to beneficial for slowing down disease progression from prediabetes to diabetes and reducing your risk of dying from cancer. However, as I mentioned earlier, higher serum levels are also associated with a plethora of negative outcomes, including an increased risk of certain forms of cancer. Raising serum levels to 26 ng/mL (~64 nmol/L) may increase the risk of pancreatic cancer, as does going up to 40 ng/mL (100 nmol/L). Getting up to 30 ng/mL (75 nmol/L) could raise your risk of developing prostate cancer.
When we add race into the mix, things get even muddier.
It is well known that people with darker skin synthesize less vitamin D in the same span of time compared to people with lighter skin. Having more melanin in your skin means that less of the UVB reaches the layer where provitamin D is found. That doesn’t mean that vitamin D is not produced though – it just means that you would need to stay outside a bit longer to really raise your vitamin D levels. If you are Black, raising your vitamin D levels likely won’t do much for your risk of developing diabetes (per this article, and this one). There is also research showing that in older Black women specifically, the risk of bone fractures goes up past 20 ng/mL (50 nmol/L).
So, what should you do?
Should you take vitamin D? Should you save your money and just go take a walk outside?
Taking all of what we went over in today’s post into account, what I can say is that aiming for healthy vitamin D levels of around 20 ng/mL isn’t a bad goal to have. Step one would of course be to get a test done. Your vitamin D levels may actually be fine, and taking too much vitamin D can lead to harmful side effects, which by now you are very familiar with. Obligatory disclaimer – I am not a medical provider, and only you and your personal medical team can really know what is best for you!
Alright, let’s wrap up this article with the answers to a few lingering questions that you may have about the sunshine vitamin.
Rapid fire question segment
How long do I need to stand outside in the sun to get enough vitamin D?
This is going to vary widely depending on factors like how much melanin you have in your skin and what part of the world you live in, but generally, you need somewhere between 5-30 minutes of exposure at least twice a week (see one, two, three, and four). Fun fact – the type of radiation that activates vitamin D in your skin, UVB, does not penetrate glass, so don’t try to get your sun exposure from behind a window.
If I’m going to buy a supplement, which one is better, D2 or D3?
Both are effective at raising vitamin D levels, but the data suggest that D3 does the job more efficiently; it’s able to raise vitamin D levels higher and do this for longer (see here, here, here, and here).
What’s the difference between D2 and D3 anyway?
D2 is made from ergosterol found in yeast, and D3 is typically made from lanolin found in sheep’s wool (see this article, and this one).
Can you overdose on Vitamin D?
If we are talking about vitamin D from the sun – no. Only so much vitamin D is produced in your skin before your body stops the conversion process. This is a good thing, otherwise you could get vitamin D toxicity just from being outside too long. Supplements are different though – it IS possible to ingest too much vitamin D. In a study of older Black, White, and Asian women, researchers found that vitamin D levels greater than or equal to 20 ng/mL were actually associated with a higher risk of fracture both Black and Asian women. Taking very high doses of vitamin D may also lead to decreased bone mineral density. In this study of about 300 people, 400 IU, 4,000 IU, and 10,000 IU doses of vitamin D were given to study participants daily for 3 years. Compared to just 400 IU per day, both of the higher doses led to decreased bone mineral density. Taking too much vitamin D (plus calcium) may also increase your risk of developing kidney stones.
Alright, that’s it for today. Take care!
References
Money spent on Vitamin D:
Vitamin D Market Size, Share Global Analysis Report, 2022-2030. (2022, December). https://www.polarismarketresearch.com/industry-analysis/vitamin-d-market
Grand View Research. (n.d.). North America Vitamin D Market Size Report, 2020-2027. https://www.grandviewresearch.com/industry-analysis/north-america-vitamin-d-market
Vitamin D Global Market Report 2023. (2023, April 4). Yahoo Finance. https://finance.yahoo.com/news/vitamin-d-global-market-report-123100398.html
Distance between sun and earth:
NASA. (2020, February 1). How Big Is the Solar System? - NASA Science. Science.nasa.gov. https://science.nasa.gov/learning-resources/how-big-is-the-solar-system/
Source for the process of vitamin D synthesis:
Engelsen O. The relationship between ultraviolet radiation exposure and vitamin D status. Nutrients. 2010 May;2(5):482-95. doi: 10.3390/nu2050482. Epub 2010 May 4. PMID: 22254036; PMCID: PMC3257661.
Link between vitamin D deficiency and pain and falls:
Charoenngam N, Shirvani A, Holick MF. Vitamin D for skeletal and non-skeletal health: What we should know. J Clin Orthop Trauma. 2019 Nov-Dec;10(6):1082-1093. doi: 10.1016/j.jcot.2019.07.004. Epub 2019 Jul 13. PMID: 31708633; PMCID: PMC6834997.
Images of children with Rickets:
Thacher, Tom. (2003). Calcium-Deficiency Rickets. Endocrine development. 6. 105-25. 10.1159/000072773. https://pubmed.ncbi.nlm.nih.gov/12964429/
Trends in vitamin D testing:
Shahangian S, Alspach TD, Astles JR, Yesupriya A, Dettwyler WK. Trends in laboratory test volumes for Medicare Part B reimbursements, 2000-2010. Arch Pathol Lab Med. 2014 Feb;138(2):189-203. doi: 10.5858/arpa.2013-0149-OA. Epub 2013 Jun 5. PMID: 23738761; PMCID: PMC4698806. https://pubmed.ncbi.nlm.nih.gov/23738761/
Huang KE, Milliron BJ, Davis SA, Feldman SR. Surge in US outpatient vitamin D deficiency diagnoses: National Ambulatory Medical Care Survey analysis. South Med J. 2014 Apr;107(4):214-7. doi: 10.1097/SMJ.0000000000000085. PMID: 24937512; PMCID: PMC4679143. https://pubmed.ncbi.nlm.nih.gov/24937512/
Recommendations for vitamin D testing:
US Preventive Services Task Force; Krist AH, Davidson KW, Mangione CM, Cabana M, Caughey AB, Davis EM, Donahue KE, Doubeni CA, Epling JW Jr, Kubik M, Li L, Ogedegbe G, Owens DK, Pbert L, Silverstein M, Stevermer J, Tseng CW, Wong JB. Screening for Vitamin D Deficiency in Adults: US Preventive Services Task Force Recommendation Statement. JAMA. 2021 Apr 13;325(14):1436-1442. doi: 10.1001/jama.2021.3069. PMID: 33847711. https://pubmed.ncbi.nlm.nih.gov/33847711/
Clifford J. Rosen, Steven A. Abrams, John F. Aloia, Patsy M. Brannon, Steven K. Clinton, Ramon A. Durazo-Arvizu, J. Christopher Gallagher, Richard L. Gallo, Glenville Jones, Christopher S. Kovacs, JoAnn E. Manson, Susan T. Mayne, A. Catharine Ross, Sue A. Shapses, Christine L. Taylor, IOM Committee Members Respond to Endocrine Society Vitamin D Guideline, The Journal of Clinical Endocrinology & Metabolism, Volume 97, Issue 4, 1 April 2012, Pages 1146–1152,
Ross AC, Manson JE, Abrams SA, Aloia JF, Brannon PM, Clinton SK, Durazo-Arvizu RA, Gallagher JC, Gallo RL, Jones G, Kovacs CS, Mayne ST, Rosen CJ, Shapses SA. The 2011 report on dietary reference intakes for calcium and vitamin D from the Institute of Medicine: what clinicians need to know. J Clin Endocrinol Metab. 2011 Jan;96(1):53-8. doi: 10.1210/jc.2010-2704. Epub 2010 Nov 29. PMID: 21118827; PMCID: PMC3046611.
Michael F. Holick, Neil C. Binkley, Heike A. Bischoff-Ferrari, Catherine M. Gordon, David A. Hanley, Robert P. Heaney, M. Hassan Murad, Connie M. Weaver, Evaluation, Treatment, and Prevention of Vitamin D Deficiency: an Endocrine Society Clinical Practice Guideline, The Journal of Clinical Endocrinology & Metabolism, Volume 96, Issue 7, 1 July 2011, Pages 1911–1930, https://doi.org/10.1210/jc.2011-0385
About Dr. Michael Holick:
Holick, M. (2024). About Michael F. Holick Ph.D., M.D. Dr. Michael F. Holick. https://drmichaelholick.org/about-dr-holick/
Biogena KG - Headquarter Salzburg. (2016, June 13). „Vitamin D – State of the art“ - Dr. Michael F. Holick in Vienna (English). YouTube. https://www.youtube.com/watch?v=NuWC2d0mTbo
New York Times article about Dr. Holick:
Szabo, L. (2018, August 18). Vitamin D, the Sunshine Supplement, Has Shadowy Money Behind It. The New York Times. https://www.nytimes.com/2018/08/18/business/vitamin-d-michael-holick.html
Concerning studies used in the Endocrine Society recommendations:
Study with 34 people:
Heaney RP, Dowell MS, Hale CA, Bendich A. Calcium absorption varies within the reference range for serum 25-hydroxyvitamin D. J Am Coll Nutr. 2003 Apr;22(2):142-6. doi: 10.1080/07315724.2003.10719287. PMID: 12672710.
Study that showed no benefit past 8ng/mL for Ca absorption:
Need AG, O'Loughlin PD, Morris HA, Coates PS, Horowitz M, Nordin BE. Vitamin D metabolites and calcium absorption in severe vitamin D deficiency. J Bone Miner Res. 2008 Nov;23(11):1859-63. doi: 10.1359/jbmr.080607. PMID: 18597633.
Medicare Coverage Database results for vitamin D:
LCD - Vitamin D Assay Testing (L39391). (2023, July 27). Www.cms.gov. https://www.cms.gov/medicare-coverage-database/view/lcd.aspx?lcdid=39391&ver=6&
Data on trends in vitamin D levels:
Forrest KY, Stuhldreher WL. Prevalence and correlates of vitamin D deficiency in US adults. Nutr Res. 2011 Jan;31(1):48-54. doi: 10.1016/j.nutres.2010.12.001. PMID: 21310306.
Cui A, Xiao P, Ma Y, Fan Z, Zhou F, Zheng J, Zhang L. Prevalence, trend, and predictor analyses of vitamin D deficiency in the US population, 2001-2018. Front Nutr. 2022 Oct 3;9:965376. doi: 10.3389/fnut.2022.965376. PMID: 36263304; PMCID: PMC9573946.
Healthcare providers recommending more vitamin D:
Souberbielle JC, Body JJ, Lappe JM, Plebani M, Shoenfeld Y, Wang TJ, Bischoff-Ferrari HA, Cavalier E, Ebeling PR, Fardellone P, Gandini S, Gruson D, Guérin AP, Heickendorff L, Hollis BW, Ish-Shalom S, Jean G, von Landenberg P, Largura A, Olsson T, Pierrot-Deseilligny C, Pilz S, Tincani A, Valcour A, Zittermann A. Vitamin D and musculoskeletal health, cardiovascular disease, autoimmunity and cancer: Recommendations for clinical practice. Autoimmun Rev. 2010 Sep;9(11):709-15. doi: 10.1016/j.autrev.2010.06.009. Epub 2010 Jul 1. PMID: 20601202.
People are spending more money on supplements:
Vitamin D: how 32 supplements really measure up. Consum Rep. 2013 May;78(5):48. PMID: 23607149. https://pubmed.ncbi.nlm.nih.gov/23607149/
Schleicher RL, Sternberg MR, Potischman N, Gahche JJ, Storandt RJ, Maw KL, Pfeiffer CM. Supplemental Vitamin D Increased Serum Total 25-Hydroxyvitamin D in the US Adult Population During 2007-2014. J Nutr. 2021 Aug 7;151(8):2446-2454. doi: 10.1093/jn/nxab147. PMID: 34036360; PMCID: PMC8349116.
Fortification of breakfast cereals:
EXTRA, EXTRA! READ ALL ABOUT IT: General Mills doubles vitamin D in Big G Cereals - General Mills. (2023, July 19). https://www.generalmills.com/news/press-releases/vitamind
Vitamin D and Osteoporosis:
Sarafrazi N, Wambogo EA, Shepherd JA. Osteoporosis or low bone mass in older adults: United States, 2017–2018. NCHS Data Brief, no 405. Hyattsville, MD: National Center for Health Statistics. 2021. DOI: https://dx.doi.org/10.15620/cdc:103477
Vitamin D and Bone Mineral Density:
Sarafrazi N, Wambogo EA, Shepherd JA. Osteoporosis or low bone mass in older adults: United States, 2017–2018. NCHS Data Brief, no 405. Hyattsville, MD: National Center for Health Statistics. 2021. DOI: https://dx.doi.org/10.15620/cdc:103477
Vitamin D and Bone Fractures:
Xu B, Radojčić MR, Anderson DB, Shi B, Yao L, Chen Y, Feng S, Lee JH, Chen L. Trends in prevalence of fractures among adults in the United States, 1999-2020: a population-based study. Int J Surg. 2024 Feb 1;110(2):721-732. doi: 10.1097/JS9.0000000000000883. PMID: 37921645; PMCID: PMC10871608.
Vitamin D for Children:
Neville H. Golden, Steven A. Abrams, COMMITTEE ON NUTRITION, Stephen R. Daniels, Steven A. Abrams, Mark R. Corkins, Sarah D. de Ferranti, Neville H. Golden, Sheela N. Magge, Sarah Jane Schwarzenberg; Optimizing Bone Health in Children and Adolescents. Pediatrics October 2014; 134 (4): e1229–e1243. 10.1542/peds.2014-2173. https://publications.aap.org/pediatrics/article/134/4/e1229/32964/Optimizing-Bone-Health-in-Children-and-Adolescents?autologincheck=redirected
Vitamin D and Diabetes:
Li X, Liu Y, Zheng Y, Wang P, Zhang Y. The effect of vitamin D supplementation on glycemic control in type 2 diabetes patients: A systematic review and meta-analysis. Nutrients 2018; 10, 375; doi:10.3390/nu10030375
Bouillon R, Manousaki D, Rosen C, Trajanoska K, Rivadeneira F, Richards JB. The health effects of vitamin D supplementation: evidence from human studies. Nat Rev Endocrinol. 2022 Feb;18(2):96-110. doi: 10.1038/s41574-021-00593-z. Epub 2021 Nov 23. PMID: 34815552; PMCID: PMC8609267.
Pittas A, Dawson-Hughes B, Sheehan P, Ware JH, Knowler WC, Aroda VR, et al. Vitamin D supplementation and prevention of type 2 diabetes. N Engl J Med 2019;381:520-30.
Dawson-Hughes, B. et al. Intratrial exposure to vitamin D and new-onset diabetes among adults with prediabetes: a secondary analysis from the Vitamin D and Type 2 Diabetes (D2d) Study. Diabetes Care 43, 2916–2922 (2020).
Pittas, A. G., Jorde, R., Kawahara, T. & Dawson-Hughes, B. Vitamin D supplementation for prevention of type 2 diabetes mellitus: to D or not to D? J. Clin. Endocrinol. Metab. 105, 3721–3733 (2020).
Zhang, Y. et al. Effects of Vitamin D supplementation on prevention of type 2 diabetes in patients with prediabetes: a systematic review and meta-analysis. Diabetes Care 43, 1650–1658 (2020).
Barbarawi, M. et al. Effect of vitamin D supplementation on the incidence of diabetes mellitus. J. Clin. Endocrinol. Metab. 105, 2857–2868 (2020).
Mousa A, Naderpoor N, de Courten MPJ, Teede H, Kellow N, Walker K, et al. Vitamin D supplementation has no effect on insulin sensitivity or secretion in vitamin D-deficient, overweight or obese adults: A randomized placebo-controlled trial. Am J Clin Nutr 2017;105:1372-81.
Seida JC, Mitri J, Colmers IN, Majumdar SR, Davidson MB, Edwards AL, et al. Effect of vitamin D3 supplementation on improving glucose homeostasis and preventing diabetes: A systematic review and meta-analysis. J Clin Endocrinol Metab 2014;99:3551-60.
Jorde R, Sollid ST, Svartberg J, Schirmer H, Joakimsen RM, Njolstad I, et al. Vitamin D 20 000 IU per week for five years does not prevent progression from prediabetes to diabetes. J Clin Endocrinol Metab 2016;101:1647-55.
NIH Factsheet:
National Institutes of Health. (2023, September 18). Vitamin D. National Institutes of Health. https://ods.od.nih.gov/factsheets/VitaminD-HealthProfessional/
Statistics About Diabetes:
American Diabetes Association. (2023, November 2). Statistics about diabetes. https://diabetes.org/about-diabetes/statistics/about-diabetes
Diabetes, Vitamin D, and Race:
Scragg R, Sowers M, Bell C; Third National Health and Nutrition Examination Survey. Serum 25-hydroxyvitamin D, diabetes, and ethnicity in the Third National Health and Nutrition Examination Survey. Diabetes Care. 2004 Dec;27(12):2813-8. PMID: 15562190. https://pubmed.ncbi.nlm.nih.gov/15562190/
Christensen MHE, Scragg RK. Consistent ethnic specific differences in diabetes risk and vitamin D status in the National Health and Nutrition Examination Surveys. J Steroid Biochem Mol Biol. 2016 Nov;164:4-10. doi: 10.1016/j.jsbmb.2015.09.023. Epub 2015 Sep 16. PMID: 26386461. https://pubmed.ncbi.nlm.nih.gov/26386461/
Vitamin D and Cancer:
Krishnan AV, Trump DL, Johnson CS, Feldman D. The role of vitamin D in cancer prevention and treatment. Endocrinol Metab Clin North Am. 2010;39:401–418.
Mehta RG, Peng X, Alimirah F, Murillo G, Mehta R. Vitamin D and breast cancer: Emerging concepts. Cancer Lett. 2012;334 (1:95–100. https://pubmed.ncbi.nlm.nih.gov/23142286/
Pereira F, Larriba MJ, Muñoz A. Vitamin D and colon cancer. Endocr Relat Cancer. 2012 May 3;19(3):R51-71. doi: 10.1530/ERC-11-0388. PMID: 22383428. https://pubmed.ncbi.nlm.nih.gov/22383428/
Cauley JA, Chlebowski RT, Wactawski-Wende J, Robbins JA, Rodabough RJ, Chen Z, et al. Calcium plus vitamin D supplementation and health outcomes five years after active intervention ended: The Women’s Health Initiative. J Womens Health 2013:22,915-29.
Stolzenberg-Solomon RZ, Vieth R, Azad A, Pietinen P, Taylor PR, Virtamo J, et al. A prospective nested case-control study of vitamin D status and pancreatic cancer risk in male smokers. Cancer Res 2006;66:10213-9.
Helzlsouer KJ for the VDPP Steering Committee. Overview of the Cohort Consortium Vitamin D Pooling Project of Rarer Cancers. Am J Epidemiol 2010;172:4-9.
Xu Y, Shao X, Yao Y, Xu L, Chang L, Jiang Z, Lin Z. Positive association between circulating 25-hydroxyvitamin D levels and prostate cancer risk: New findings from an updated meta-analysis. J Cancer Res Clin Oncol 2014;140:1465-77. https://pubmed.ncbi.nlm.nih.gov/24838848/
Manson, J. E. et al. Vitamin D supplements and prevention of cancer and cardiovascular disease. N. Engl. J. Med. 380, 33–44 (2019). https://pubmed.ncbi.nlm.nih.gov/30415629/
Scragg, R. et al. Monthly high-dose vitamin D supplementation and cancer risk: a post hoc analysis of the vitamin D assessment randomized clinical trial. JAMA Oncol. 4, e182178 (2018). https://pubmed.ncbi.nlm.nih.gov/30027269/
Bjelakovic, G. et al. Vitamin D supplementation for prevention of cancer in adults. Cochrane Database Syst. Rev. 6, CD007469 (2014). https://pubmed.ncbi.nlm.nih.gov/24953955/
Vitamin D and Heart Disease:
Chowdhury, R. et al. Vitamin D and risk of cause specific death: systematic review and meta-analysis of observational cohort and randomised intervention studies. BMJ 348, g1903 (2014).
Barbarawi M, Kheiri B, Zayed Y, Barbarawi O, Dhillon H, Swaid B, Yelangi A, Sundus S, Bachuwa G, Alkotob ML, Manson JE. Vitamin D Supplementation and Cardiovascular Disease Risks in More Than 83 000 Individuals in 21 Randomized Clinical Trials: A Meta-analysis. JAMA Cardiol. 2019 Aug 1;4(8):765-776. https://pubmed.ncbi.nlm.nih.gov/31215980/
Sluyter, J. D. et al. Effect of monthly, high-dose, long-term vitamin D supplementation on central blood pressure parameters: a randomized controlled trial substudy. J. Am. Heart Assoc. 6, e006802 (2017). https://pubmed.ncbi.nlm.nih.gov/29066444/
Manson, J. E. et al. Vitamin D supplements and prevention of cancer and cardiovascular disease. N. Engl. J. Med. 380, 33–44 (2019). https://pubmed.ncbi.nlm.nih.gov/30415629/
Scragg R, Stewart AW, Waayer D, Lawes CMM, Toop L, Sluyter J, et al. Effect of monthly high-dose vitamin D supplementation on cardiovascular disease in the Vitamin D Assessment Study: A randomized clinical trial. JAMA Cardiol 2017;2:608-16.
More on Vitamin D and Bone Health:
Bolland, M. J., Grey, A. & Avenell, A. Effects of vitamin D supplementation on musculoskeletal health: a systematic review, meta-analysis, and trial sequential analysis. Lancet Diabetes Endocrinol. 6, 847–858 (2018). https://pubmed.ncbi.nlm.nih.gov/30293909/
Boonen, S. et al. Need for additional calcium to reduce the risk of hip fracture with vitamin D supplementation: evidence from a comparative metaanalysis of randomized controlled trials. J. Clin. Endocrinol. Metab. 92, 1415–1423 (2007).
Bolland, M. J., Grey, A., Gamble, G. D. & Reid, I. R. The effect of vitamin D supplementation on skeletal, vascular, or cancer outcomes: a trial sequential meta-analysis. Lancet Diabetes Endocrinol. 2, 307–320 (2014). https://pubmed.ncbi.nlm.nih.gov/24703049/
Avenell, A., Mak, J. C. & O’Connell, D. Vitamin D and vitamin D analogues for preventing fractures in post-menopausal women and older men. Cochrane Database Syst. Rev. 4, CD000227 (2014). https://pubmed.ncbi.nlm.nih.gov/24729336/
Yao, P. et al. Vitamin D and calcium for the prevention of fracture: a systematic review and meta-analysis. JAMA Netw. Open 2, e1917789 (2019). https://pubmed.ncbi.nlm.nih.gov/31860103/
Chakhtoura, M., Chamoun, N., Rahme, M. & Fuleihan, G. E. Impact of vitamin D supplementation on falls and fractures–a critical appraisal of the quality of the evidence and an overview of the available guidelines. Bone 131, 115112 (2020). https://pubmed.ncbi.nlm.nih.gov/31676406/
Guirguis-Blake JM, Michael YL, Perdue LA, Coppola EL, Beil TL. Interventions to prevent falls in older adults: Updated evidence report and systematic review for the US Preventive Services Task Force. JAMA 2018;319:1705-16. https://pubmed.ncbi.nlm.nih.gov/29710140/
U.S. Preventive Services Task Force. Interventions to prevent falls in community-dwelling older adults. US Preventive Services Task Force recommendation statement. JAMA 2018;319:1696-1704. https://pubmed.ncbi.nlm.nih.gov/29710141/
Gallagher JC. Vitamin D and bone density, fractures, and falls: The end of the story? Lancet Diabetes Endocrinol 2018;6:834-5. https://pubmed.ncbi.nlm.nih.gov/30293910/
LeBoff MS, Chou SH, Ratliff KA, Cook NR, Khurana B, Kim E, et al. Supplemental vitamin D and incident fractures in midlife and older adults. N Eng J Med 2022;387:299-309.
Reid, I. R. et al. Effect of monthly high-dose vitamin D on bone density in community-dwelling older adults substudy of a randomized controlled trial. J. Intern. Med. 282, 452–460 (2017). https://pubmed.ncbi.nlm.nih.gov/28692172/
Macdonald, H. M. et al. 25-hydroxyvitamin D threshold for the effects of vitamin D supplements on bone density: secondary analysis of a randomized controlled trial. J. Bone Miner. Res. 33, 1464–1469 (2018). https://pubmed.ncbi.nlm.nih.gov/29665087/
Bischoff-Ferrari HA, Willett WC, Wong JB, Giovannucci E, Dietrich T, Dawson-Hughes B. Fracture prevention with vitamin D supplementation: a meta-analysis of randomized controlled trials. JAMA. 2005 May 11;293(18):2257-64. doi: 10.1001/jama.293.18.2257. PMID: 15886381.
Study on bone health in Black women:
Aloia, J. et al. Vitamin D supplementation in elderly Black women does not prevent bone loss: a randomized controlled trial. J. Bone Miner. Res. 33, 1916–1922 (2018).
Vitamin D and Depression:
Anglin RES, Samaan Z, Walter SD, McDonald SD. Vitamin D deficiency and depression in adults: Systematic review and meta-analysis. The British Journal of Psychiatry 2013;202:100-7
Gowda U, Mutowo MP, Smith BJ, Wluka AE, Renzaho AMN. Vitamin D supplementation to reduce depression in adults: Meta-analysis of randomized controlled trials. Nutrition 2015;31:421-9. https://pubmed.ncbi.nlm.nih.gov/25701329/
Jorde R, Kubiak J. No improvement in depressive symptoms by vitamin D supplementation: Results from a randomised controlled trial. Journal of Nutrition Science 2018;7:1-7.
de Koning EJ, Lips P, Penninx BWJH, Elders PJM, Heijboer AC, den Heijer M, et al. Vitamin D supplementation for the prevention of depression and poor physical function in older persons: The D-Vitaal study, a randomized clinical trial. Am J Clin Nutr 2019;110:1119-30.
Jorde R, Grimnes G. Vitamin D: No cure for depression. Am J Clin Nutr 2019;110:1043-4. PMID: 31504098. https://pubmed.ncbi.nlm.nih.gov/31504098/
Okereke OI, Reynolds III CF, Mischoulon D, Chang G, Vyas CM, Cook NR, et al. Effect of long-term vitamin D3 supplementation vs placebo on risk of depression or clinically relevant depressive symptoms and on change in mood scores: A randomized clinical trial. JAMA 2020;324:471-80. https://pubmed.ncbi.nlm.nih.gov/32749491/
Vitamin D and Multiple Sclerosis:
Munger K, Hongell K, Aivo J, Soilu-Hanninen M, Surcel H-M, Ascherio A. 25-hydroxyvitamin D deficiency and risk of MS among women in the Finnish Maternity Cohort. Neurology 2017;89: 1578-83. https://pubmed.ncbi.nlm.nih.gov/28904091/
Munger KL, Levin LI, Hollis BW, Howard NS, Ascherio A. Serum 25-hydroxyvitamin D levels and risk of multiple sclerosis. JAMA 2006;296:2832-8. https://pubmed.ncbi.nlm.nih.gov/17179460/
Salzer J, Hallmans G, Nystrom M, Stenlund H. Wadell G, Sundstrom P. Vitamin D as a protective factor in multiple sclerosis. Neurology 2012;79:2140-5.
Jagannath VA, Filippini G, Di Pietrantonj C, Asokan GV, Robak EW, Whamond L, Robinson SA. Vitamin D for the management of multiple sclerosis (review). Cochrane Database of Systematic Reviews 2018, issue 9, Art. No.: CD008422. DOI: 10.1002/14651858.CD008422.pub3. https://pubmed.ncbi.nlm.nih.gov/30246874/
Vitamin D and COVID-19:
Pereira M, Dantas Damascena A, Galvão Azevedo LM, de Almeida Oliveira T, da Mota Santana J. Vitamin D deficiency aggravates COVID-19: systematic review and meta-analysis. Crit Rev Food Sci Nutr. 2022;62(5):1308-1316.
Vitamin D and Infant Size:
Bodnar LM, Catov JM, Zmuda JM, Cooper ME, Parrott MS, Roberts JM, Marazita ML, Simhan HN. Maternal serum 25-hydroxyvitamin D concentrations are associated with small-for-gestational age births in white women. J Nutr. 2010 May;140(5):999-1006. doi: 10.3945/jn.109.119636. Epub 2010 Mar 3. PMID: 20200114; PMCID: PMC2855265.
Thorne-Lyman A, Fawzi WW. Vitamin D during pregnancy and maternal, neonatal and infant health outcomes: a systematic review and meta-analysis. Paediatr Perinat Epidemiol. 2012 Jul;26 Suppl 1(0 1):75-90. doi: 10.1111/j.1365-3016.2012.01283.x. PMID: 22742603; PMCID: PMC3843348.
Vitamin D conversion and skin color:
Engelsen O. The relationship between ultraviolet radiation exposure and vitamin D status. Nutrients. 2010 May;2(5):482-95. doi: 10.3390/nu2050482. Epub 2010 May 4. PMID: 22254036; PMCID: PMC3257661.
How to get enough sun exposure:
Tsiaras WG, Weinstock MA. Factors influencing vitamin D status. Acta Derm Venereol. 2011 Mar;91(2):115-24. doi: 10.2340/00015555-0980. PMID: 21384086.
Holick MF. Vitamin D deficiency. N Engl J Med 2007;357:266-81.
Bouillon R. Comparative analysis of nutritional guidelines for vitamin D. Nat Rev Endocrinol 2017;13:466-79. https://pubmed.ncbi.nlm.nih.gov/28387318/
U.S. Department of Health and Human Services. The Surgeon General’s Call to Action to Prevent Skin Cancer. Washington, DC: U.S. Dept of Health and Human Services, Office of the Surgeon General; 2014. https://www.hhs.gov/sites/default/files/call-to-action-prevent-skin-cancer.pdf
Hossein-nezhad A, Holick MF. Vitamin D for health: A global perspective. Mayo Clin Proc 2013;88:720-55. https://pubmed.ncbi.nlm.nih.gov/23790560/
Vitamin D2 versus Vitamin D3:
Tripkovic L, Lambert H, Hart K, Smith CP, Bucca G, Penson S, et al. Comparison of vitamin D2 and vitamin D3 supplementation in raising serum 25-hydroxyvitamin D status: A systematic review and meta-analysis. Am J Clin Nutr 2012;95:1357-64.
Lehmann U, Hirche F, Stangl GI, Hinz K, Westphal S, Dierkes J. Bioavailability of vitamin D2 and D3 in healthy volunteers, a randomised placebo-controlled trial. J Clin Endocrin Metab 2013;98:4339-45. https://pubmed.ncbi.nlm.nih.gov/24001747/
Logan VF, Gray AR, Peddie MC, Harper MJ, Houghton LA. Long-term vitamin D3 supplementation is more effective than vitamin D2 in maintaining serum 25-hydroxyvitamin D status over the winter months. Br J Nutr 2013;109:1082-8.
Tripkovic L, Wilson LR, Hart K, Johnsen S, de Lusignan S, Smith CP, et al. Daily supplementation with 15 µg vitamin D2 compared with vitamin D3 to increase wintertime 25-hydroxyvitamin D status in healthy South Asian and white European women: A 12-wk randomized, placebo-controlled food-fortification trial. Am J Clin Nutr 2017;106:481-90.
Holick MF. Vitamin D deficiency. N Engl J Med 2007;357:266-81.
Hirsch AL. Industrial Aspects of Vitamin D. In: Feldman D, Pike JW, Adams JS, eds. Vitamin D. 3rd ed. Academic Press; 2011:73-93.
What can happen if you take too much vitamin D:
Cauley JA, Danielson ME, Boudreau R, Barbour KE, Horwitz MJ, Bauer DC, Ensrud KE, Manson JE, Wactawski-Wende J, Shikany JM, Jackson RD. Serum 25-hydroxyvitamin D and clinical fracture risk in a multiethnic cohort of women: the Women's Health Initiative (WHI). J Bone Miner Res. 2011 Oct;26(10):2378-88. doi: 10.1002/jbmr.449. PMID: 21710614; PMCID: PMC3304434. https://pubmed.ncbi.nlm.nih.gov/21710614/
Burt LA, Billington EO, Rose MS, Raymond DA, Hanley DA, Boyd SK. Effect of High-Dose Vitamin D Supplementation on Volumetric Bone Density and Bone Strength: A Randomized Clinical Trial. JAMA. 2019 Aug 27;322(8):736-745. doi: 10.1001/jama.2019.11889. Erratum in: JAMA. 2019 Nov 19;322(19):1925. PMID: 31454046; PMCID: PMC6714464.
Letavernier E, Daudon M. Vitamin D, Hypercalciuria and Kidney Stones. Nutrients. 2018 Mar 17;10(3):366. doi: 10.3390/nu10030366. PMID: 29562593; PMCID: PMC5872784.
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