By Dr. Mercola
Over the past couple of decades, tens of thousands of studies have evaluated the benefits of vitamin D, linking low blood levels to a whole host of chronic health conditions. In fact, this site was one of the leaders helping to catalyze interest in vitamin D over 15 years ago. Today, many doctors have finally caught on and are taking vitamin D seriously; testing their patients and recommending supplementation when necessary. The progress made makes the present backlash all the more shocking and disappointing.
"Many Americans Taking Too Much Vitamin D," Reuters recently announced.1 "More people than ever are taking way too much vitamin D," Popular Science declared, adding, "You may have a deficiency, but overdosing isn't the answer."2 ABC News warned its viewers that taking more than 4,000 international units (IUs) of vitamin D is "far above safe levels," and could potentially cause heart disease.3 Ditto for Consumer Affairs4 and many others.5,6
Where is this coming from? If you've followed the progression of vitamin D science, you will be aware of the fact that recommended vitamin D levels — and the dosages typically needed to achieve those levels if you're not getting regular sun exposure — have dramatically risen over the years.
Researchers have also pointed out a basic mathematical flaw that led to vitamin D recommendations being underestimated by a factor of 10. Unfortunately, the study now being promoted by the media takes none of these things into consideration, instead promulgating decades' old fallacies.
Are Americans Taking Too Much Vitamin D?
According to the featured study,7 nearly 20 percent of American adults are taking supplemental vitamin D, and many are taking "excessively high doses" — amounts linked to "an increased risk of fractures, falls, kidney stones and certain cancers" — even an increased risk of death from all causes.8
An "excessively high dose," the study warns, is anything over 4,000 IUs a day, adding that this is the maximum recommended dosage, and that anything higher than this may result in dangerous side effects. Senior author Pamela Lutsey, public health researcher at the University of Minnesota in Minneapolis, told Reuters:
"Vitamin D is essential for bone metabolism, as it helps the body absorb calcium and maintain appropriate concentrations of calcium and phosphate in the blood. Excessive intake of vitamin D can, however, be harmful, as it can cause overabsorption of calcium. Excess blood calcium can, in turn, lead to detrimental deposition of calcium in soft tissues, such as the heart and kidneys."
Reuters does note that the study was "not a controlled experiment designed to examine the risks and benefits of varying amounts of vitamin D supplementation." Unfortunately, that important piece of information is likely to get lost in the fearmongering, no matter how flawed the conclusions.
For starters, the study's authors assume the vitamin D dosage recommended by the National Academy of Medicine (NAM; formerly the Institute of Medicine, IOM) is scientifically substantiated. As it turns out, it is not, and dedicated vitamin D researchers have for a long time urged NAM to update its recommendation, as it is based on flawed math.
Flawed Math Vastly Underestimates Vitamin D Need
In this video, Keith Baggerly, Ph.D., explains the key problems with respect to NAM's stance on vitamin D requirements. You can also read his report here. NAM (formerly IOM) chose 20 nanograms per milliliter (ng/mL) of serum concentration of 25-hydroxy vitamin D as an adequate level for bone health, and to maintain a level of 20 ng/mL, NAM says you need to take 600 IUs a day up to age 70, and 800 IUs if you're over 70. However, both of these measures are too low due to a mathematical error.
Using the same raw data, and correcting the math, you get an estimate of about 30 ng/mL as an adequate level for bone health, and given the logarithmic nature of the dose response curve for vitamin D, increasing the target serum level by 50 percent may require increasing the RDI in IUs by several times.
In 2014, two investigators from the University of Edmonton published a paper9 that explicitly showed NAM had made a calculation error in defining the intake needed to reach and maintain 20 ng/mL. Had it been calculated correctly, the RDI would have been at least 10 times greater than what was publically posted.
Importantly, 30 ng/mL is merely indicated for bone health; it may not be sufficient for general health or diseases prevention. When studying a native African tribe, the physiological levels were found to be in the 40 to 60 ng/mL range, which is the range suggested by GrassrootsHealth's panel of experts for general health. As explained by the late Dr. Robert Heaney in a previous interview (included below for your convenience):
"The [RDI], as I think most of us know, is the intake that is reckoned to be necessary to meet the nutritional need of 97.5 percent of the population … How much is enough? The [IOM, now NAM] said 600 IUs was enough. But what's very clear is that 600 IUs would not get 97.5 percent of the population above 20 ng/mL. That's what the Edmonton investigators showed.
As a matter of fact … as many as half of the people getting 600 IUs a day wouldn't get up to 20 ng/mL … The Edmonton investigators calculated a number of 8,895 IUs per day, using the same set of studies on which the IOM had based its calculation ... When I was able to access the GrassrootsHealth (GRH) data, a completely different set from the one used by the IOM, we could directly calculate the intake needed …
That's because, in the GRH database, we know exactly how much of an increase in 25-hydroxy D the participants got on whatever dose they were taking. Our calculation showed that about 3,800 IUs per day, in addition to everything they were already getting [from sun and food], would have been necessary to get 97.5 percent of that population to 20 ng/mL.
Factoring in the basal intake in the GRH population, we showed that you need about 7,000 IUs per day in order to get 97.5 percent above 20 ng/mL. That's very close to the figure that the Edmonton investigators had used: 8,895 [IUs]."
The public health implications are tremendous. The National Academy of Sciences (NAS) has created a statistical panel to review NAM's calculations. This panel has now completed its review, but the results have not yet been made public. It is imperative that the panel's results be published as soon as possible, especially in light of the current misinformation being disseminated, suggesting Americans may be taking dangerously high levels of vitamin D, when in fact most are not getting nearly enough.
NAM Needs to Own Up to Its Mistake and End Catastrophic Misinformation Campaign
Heaney would know what he was talking about, seeing how he was one of the leading, most well-recognized vitamin D researchers in the world. Up until his death he was also the research director of GrassrootsHealth, which is compiling data from a number of population-based studies like the D*Action project.
Trained as a clinical endocrinologist, Heaney spent a large part of the last 50 years of his life doing clinical research, most of it in the field of vitamin D, working on quantifying the vitamin D economy. This includes defining:
- How much vitamin D is necessary to reach a certain effect
- How large of an effect you might get at a particular dosage
- How much vitamin D you make in your skin in response to sunlight
- How long it lasts
Heaney and colleagues challenged NAM's vitamin D recommendation,10 warning the RDI underestimates need by a factor of 10. Most vitamin D experts also agree that a serum level of 20 ng/mL is too low for optimal health, which means the requirement for most people is even higher than that.
Moreover, any public guidance on vitamin D really should be based on your blood level, not a daily dosage, because the dosage response from one person to the next can vary significantly. As noted in a 2015 study evaluating the response to vitamin D supplementation:11
"In response to a given dose of vitamin D, the effect on 25(OH)D concentration differs between individuals … For this review, a comprehensive literature search was conducted to identify those factors and to explore their significance in relation to circulating 25(OH)D response to vitamin D supplementation …
Response to vitamin D supplementation can be explained by several environmental and demographic factors. Recently, Zittermann et al. (2014) published a systematic review concerning the importance of body weight for the dose-response relationship with circulating 25(OH)D.
The authors demonstrated that 34.5 percent of variation in circulating 25(OH)D was explained by body weight, followed by type of supplement (D2 or D3) (9.8 percent), age (3.7 percent), calcium intake (2.4 percent) and basal 25(OH)D concentrations (1.9 percent), leaving approximately 50 percent of the variations to unknown factors."
One such unknown factor could be related to differences in single nucleotide polymorphisms (SNPS), a common genetic variation. At any rate, the only way to ensure you're taking a dose that is appropriate for you is to test your blood level, which should be between 40 and 60 ng/mL year-round.
Research suggests potential toxicity does not occur until you reach a level of about 200 ng/mL, and no evidence of toxicity has been found in trials using dosages of 10,000 IUs a day12,13 — a far cry from the recommended maximum of 4,000 IUs a day.
What Is an Ideal Vitamin D Level?
Based on the accumulated data collected and research done by GrassrootsHealth, a vitamin D level of 40 ng/mL is a more appropriate minimum level. To prevent chronic disease and optimize health, a level between 40 and 60 ng/mL appears to be ideal. According to Heaney, evidence shows that 20 ng/mL is not even adequate for the prevention of osteomalacia.
"The point is the [IOM, now NAM] is dead wrong; not because it chose the wrong number, but because it made a mathematical mistake. They miscalculated, which is really kind of embarrassing if you think about it. Somebody didn't check the work," Heaney says.
"Now, having made that mistake, bureaucrats being bureaucrats, they're unlikely to want to change. They're not going to say, 'Oops, we made a mistake. Here is the right answer.' They seem to say, 'We are not wrong, [and] if no federal agency asks to have it reviewed, it could be 10 years from now before anybody ever looks at it again.'"
Lutsey's study is a perfect example of why NAM needs to rectify its mistake. We cannot move forward when researchers are making assumptions based on flawed recommendations. That Lutsey was unaware of this mathematical error just goes to show that scientists cannot keep up with all the relevant papers being published relating to vitamin D. Lutsey also ignores the many studies showing higher vitamin D levels in fact correlate with improved health outcomes and a lower risk of all-cause mortality, not higher risks.
The Interplay of Vitamin D, Calcium, Magnesium and Vitamin K2
Lutsey points out that excessive vitamin D may cause overabsorption of calcium, which in turn may result in calcium deposits in your heart and kidneys. Indeed, it is important to maintain not only the proper balance of vitamin D and calcium, but also magnesium and vitamin K2. Lack of balance between these four nutrients is why calcium supplements have become associated with increased risk of heart attack and stroke, and why some experience symptoms of "vitamin D toxicity."
I use quotation marks here, because the problem is not so much excess vitamin D as it is a lack of vitamin K2. Part of the explanation for these adverse side effects is that vitamin K2 keeps calcium in its appropriate place. If you're K2 deficient, added calcium can cause more problems than it solves, by accumulating in the wrong places. Similarly, taking megadoses of vitamin D supplements without sufficient amounts of K2 can lead to inappropriate calcification, which is what Lutsey is alluding to.
While the optimal ratios between vitamin D and vitamin K2 have yet to be established, Dr. Kate Rheaume-Bleue (whom I've interviewed on this topic) suggests that for every 1,000 IUs of vitamin D you take, you may benefit from about 100 micrograms of K2, and perhaps as much as 150 to 200 micrograms (mcg).
Maintaining an appropriate calcium-to-magnesium ratio is also important, as magnesium helps keep calcium in your cells so they can function better. Historically, mankind ate a diet with a calcium-magnesium ratio of 1-to-1,14 but Americans tend to have a higher calcium-to-magnesium ratio in their diet, averaging about 3.5-to-1.
Magnesium and vitamin K2 also complement each other, as magnesium helps lower blood pressure, which is an important component of heart disease. So, all in all, anytime you're taking any of the following: magnesium, calcium, vitamin D3 or vitamin D2, you need to take all the others into consideration as well, since these all work synergistically with each other.
Discouraging Vitamin D Supplementation Is Inadvisable
So, to recap:
The best way to optimize your vitamin D levels is to expose enough of your skin for long enough periods to increase your vitamin D levels so they are between 40 and 60 ng/mL.
If you cannot get adequate sun exposure, then it would be wise to use oral vitamin D3 in the dosage recommended below
Current RDI for oral vitamin D underestimates need by a factor of 10 due to a simple mathematical error. Correcting this error would result in an RDI of 6,000 IUs, and 8,000 IUs if you're over 70
Ideal dosage can only be determined through blood testing, as dosage response to supplemental vitamin D varies widely from one person to the next
You need a blood level of at least 40 ng/mL to significantly impact your risk of chronic disease, including heart disease, cancer and all-cause mortality
No toxicity has been found in trials using 10,000 IUs per day of vitamin D, and toxicity does not become a concern until you reach a level of about 200 ng/mL
The risk of calcification is ameliorated by taking vitamin D supplements with vitamin K2 and balancing your calcium and magnesium ratios
Considering this, the notion that many Americans are endangering their health by taking in excess of 4,000 IUs of vitamin D per day is unreasonable at best. Research shows higher vitamin D levels can help prevent and/or treat:
Dry eye syndromes15,16 and macular degeneration17,18
Neurodegenerative diseases, including multiple sclerosis19,20
Gastrointestinal diseases and related cancers21
Infectious diseases, including influenza and HIV22,23
Inflammatory rheumatic diseases24
Neurological diseases such as Alzheimer's disease25,26 and epilepsy
In one study,27 epileptics given a one-time megadose of vitamin D3, ranging from 40,000 IUs all the way up to 200,000 IUs, followed by a daily dose of 2,000 to 2,600 IUs a day for three months, to bring each individual's vitamin D status to at least 30 ng/ml, resulted in significant improvements.
Ten out of 13 had a decrease in the number of seizures, five of which experienced more than a 50 percent reduction. Overall, the group had a 40 percent reduction in the number of seizures
According to researchers in Cairo,28 most patients with systemic lupus erythematosus have some level of vitamin D deficiency, defined as a level of 10 ng/mL or less, or insufficiency, a level between 10 and 30 ng/mL
A vitamin D level below 20 ng/mL may raise your risk for depression by as much as 85 percent, compared to having a vitamin D level greater than 30 ng/mL
Optimizing your vitamin D during pregnancy is crucial not only for your own health, but also for the short- and long-term health of your child.29
Studies30 reveal you need a vitamin D level above 40 ng/mL to protect your baby from serious complications such as premature delivery and preeclampsia, and studies have confirmed there's a lifelong impact of vitamin D deficiency in pregnancy — ranging from childhood asthma,31,32 colds and flu, dental cavities, diabetes and even strokes and cardiovascular disease33,34 in later life
Studies indicate a dosage range of 1,100 to 4,000 IUs a day and a serum 25-hydroxyvitamin D concentration of 60 to 80 ng/mL may be needed to reduce cancer risk.
One 2011 study35 led by vitamin D experts Drs. Cedric Garland and Heaney found the supplemental dose ensuring 97.5 percent of the study population achieved a vitamin D blood level of at least 40 ng/mL was 9,600 IU/day. It also concluded that intake of up to 40,000 IUs per day is unlikely to result in vitamin D toxicity.
Vitamin D also helps improve health outcomes for cancer patients. A 2009 study36 showed cancer-free survival during four years of follow-up was 77 percent higher among patients receiving calcium and vitamin D supplements compared to those receiving a placebo.
Here, the minimum year-round blood level of vitamin D required to prevent breast and colorectal cancers was 40 to 60 ng/mL. According to the authors, "The time has arrived for nationally coordinated action to substantially increase intake of vitamin D and calcium."
Breast37 and prostate38,39 cancers are just two examples where low vitamin D also renders you more vulnerable to more aggressive forms of the disease. Recent research40 has also found that low vitamin D levels are associated with more severe peripheral neuropathy in cancer patients
Falls, fractures, dental health and more
A 2006 review41 looking at vitamin D intakes and health outcomes such as bone mineral density, dental health, risk of falls, fractures and colorectal cancer, found "the most advantageous serum concentrations of 25(OH)D begin at 30 ng/mL, and the best are between 36 to 40 ng/mL"
Research42 has shown vitamin D supplementation (4,000 IUs/day) combined with resistance training helps decrease your waist-to-hip ratio — a measurement that is far better at determining your risk for type 2 diabetes and heart disease than BMI
Abdominal obesity in combination with a low vitamin D level has also been shown to "synergistically influence" your risk of insulin resistance.43 According to this study, 47 percent of the increased odds of insulin resistance can be explained by the interaction between insufficient vitamin D levels and a high BMI
A meta-analysis44 of 42 randomized controlled trials found supplemental vitamin D significantly reduced mortality from all causes when taken for a minimum of three years
Vitamin D and Omega-3 — Two Crucial Nutrients for Optimal Health
Considering there are well over 30,000 studies on vitamin D, and vitamin D receptors have been found in virtually all bodily tissues, from your brain to your bones, the above list is far from complete. The main point is that your risk of experiencing adverse effects from vitamin D supplementation are slim, and the notion that people are endangering their health by taking 4,000 IUs or more of vitamin D3 per day is not supported by a majority of the evidence.
On the contrary, vitamin D experts are becoming increasingly convinced that an ideal vitamin D blood level is somewhere between 40 and 60 ng/mL, and the most appropriate dosage is whatever dosage will put you within that range. For some, that may be 2,000 IUs a day; for others it may be 10,000 IUs.
I don't know ANY single physical factor that could improve your health more than understanding and finally applying what we now know about vitamin D. Getting your blood levels tested and making sure your vitamin D levels are in the optimal range is especially important, no matter what your age is, or where you live.
GrassrootsHealth has now released a consumer-sponsored research kit that includes both vitamin D and omega-3. This kit is part of the D*Action + Omega-3 Project, and you can get it either from my online store or directly from GrassrootsHealth. To learn more about this project, see their FAQ page.
Vitamin D and omega-3 are two of the most important nutrients your body needs to maintain optimal health, and the only way to evaluate your status is to test them. GrassrootsHealth D*Action + Omega-3 Project is the largest project in the world that allows scientific researchers to study the links between these nutrients, and participating in the project is an inexpensive way to take control of your health and help advance science at the same time.