Vitamin D Nonsense
On November 20th, the "prestigious" Institute of Medicine of the National Academies of Science (IOM) issued its eagerly awaited report on Dietary Reference Intakes for Calcium and Vitamin D. According to the study brief, "Calcium and vitamin D are two essential nutrients long known for their role in bone health. But since 2000, the public has heard conflicting messages about other benefits of these nutrients -- especially vitamin D -- and also about how much calcium and vitamin D they need to be healthy." And in fact, it was to help clarify this issue that the United States and Canadian governments asked the IOM to assess the current data on health outcomes associated with calcium and vitamin D, as well as update the nutrient reference values, known as Dietary Reference Intakes (DRIs).
In their report, the IOM proposed new reference values that the study's authors claim are based on much more information and higher-quality studies than were available when the values for these nutrients were first set in 1997. The IOM found that the evidence supports a role for vitamin D and calcium in bone health but not in other health conditions and not in significantly higher amounts.
As we will discuss, at least part of this conclusion is just plain silly -- the rest merely illogical. Unsurprisingly, the mainstream press simply parroted back a summary of the report with the usual over-the-top headlines:
- Vitamin D Report Shocker: High Doses Unnecessary, Risky (CBS)
- Extra vitamin D and calcium pills may do more harm than good (CNN)
- North Americans get enough calcium, vitamin D (Reuters)
But enough of picking on the press! It is now perfectly clear that the mainstream media no longer has the budget to support "investigative" journalism, with the possible exception of one or two major stories a year. All that can be expected when it comes to health and nutrition is that they parrot back the "news" they are given. That means that when a credentialed organization such as the IOM issues a report, the press will merely rework the press release issued by the researchers, add a "sexy" headline, and publish it as fact -- unquestioned, unexplored, and unchallenged. Unfortunately, that means that a lot of nonsense gets reported as "health fact" since credentials don't guarantee competence. In fact, they often mean corporate ties, hidden agendas, and huge bias. That means that if you want to truly understand the real story, you have to dig deeper and look at the underlying facts yourself or turn to alternative sources of information that you trust.
Interestingly, one such alternative source, the Council for Responsible Nutrition, a major spokes-group for the dietary supplement industry, was obsequiously cautious in their response to the IOM report, stating that the modestly increased DRI recommendations in the study were a step in the right direction, but regrettably fell short. "Regrettably fell short"? That's the best you can do? Fortunately, after opening their response by sounding like a bunch of wusses (thank you Ed Rendell), they then went on to express some stronger concerns about the report. Unfortunately, they never actually confronted the serious flaws in the study that render all of its recommendations totally meaningless. So let's look at those flaws now.
Flaws in the IOM vitamin D study
(Note: I've discussed calcium in detail in several previous newsletters, so we'll focus on just the vitamin D aspects of the IOM study in this newsletter.)
The study's conclusions rest on four foundational pillars -- all of which I disagree with:
- That vitamin D2 and D3 are interchangeable.
- That previous studies ascribing health benefits to higher levels of vitamin D supplementation are contradictory and flawed.
- That most Americans are maintaining serum 25 hydroxy vitamin D (25OHD) levels in the desirable 40 to 50 nmol/L range. Note: 25OHD is the recognized biomarker for vitamin D levels in the human body.
- That supplemental vitamin D above 600-800 IU is inherently useless and unsafe (with up to 4,000 allowed under exceptional circumstances).
So let's take these four pillars on one at a time.
Vitamin D2 and D3 are interchangeable?
To quote from the study:
"Vitamin D, also known as calciferol, comprises a group of fat-soluble seco-sterols. The two major forms are vitamin D2 and vitamin D3. Vitamin D2 (ergocalciferol) is largely human-made and added to foods, whereas vitamin D3 (cholecalciferol) is synthesized in the skin of humans from 7-dehydrocholesterol and is also consumed in the diet via the intake of animal-based foods. Both vitamin D3 and vitamin D2 are synthesized commercially and found in dietary supplements or fortified foods. The D2 and D3 forms differ only in their side chain structure. The differences do not affect metabolism (i.e., activation) and both forms function as prohormones. When activated, the D2 and D3 forms have been reported to exhibit identical responses in the body."
Quite simply, this is not true. Vitamin D2 is much less effective in humans than D3. In fact, the metabolic pathways for D2 and D3 in the human body are clearly understood by the scientific community and are known to be anything but identical. The net result is that vitamin D2's potency is less than one third that of vitamin D3. But that's not all. The IOM report further states:
"The utility of serum 25OHD level as a biomarker of effect is less certain. Prentice et al. (2008) pointed out that the adequacy of the vitamin D supply in meeting functional requirements depends upon many factors, including the uptake of 25OHD by target cells, the rate of conversion of calcitriol and its delivery to target tissues, the expression and affinity of the VDR in target tissues, the responsiveness of cells to the activated VDR, and the efficiency of induced metabolic pathways. Nonetheless, despite these uncertainties, serum 25OHD levels can be regarded as a useful tool in considering vitamin D requirements; in fact, such measures are virtually the only tool available at this time."
Amusingly, this is actually a bit of a dance by the committee in regard to their own conclusions concerning the "identical" nature of D2 and D3. If you read between the lines, what they're saying is that D2 and D3 are only identical if you restrict your comparison to short term 25OHD levels. In other words, calling them identical requires you to close your eyes to all contradictory evidence.
So what am I talking about?
As it turns out, in addition to having markedly lower potency, D2 also has a significantly shorter duration of action relative to vitamin D3, which shows up in 25OHD levels…if you care to look. Specifically, both forms of vitamin D produce similar initial rises in serum 25OHD over the first 3 days. But 25OHD continues to rise with D3 supplementation, peaking at 14 days, whereas serum 25OHD falls rapidly in D2 treated subjects. In fact, levels fall so far with D2 supplementation that they are no different from baseline at 14 days.
This is proof positive that even a layman can understand that D2 and D3 are not metabolically identical in the human body. Is this important? You bet it is since this fact alone undercuts all of the IOM study's conclusions, as well as the committee's analysis of the existing body of work vis-à-vis vitamin D. As a fun side note, the prescription form of vitamin D is ergocalciferol, or vitamin D2, not the more effective human form, vitamin D3 or cholecalciferol. It's brilliant when you think about it! You pay a doctor several hundred dollars for a visit so he can prescribe vitamin D for you. You then have to pay over 20 times as much money for the prescription form of vitamin D that's only one third as effective as the stuff you can buy in the health food store for a fraction of the amount -- and without the need to pay a doctor for the prescription in the first place. Ya gotta love it!
The bottom line, as clearly stated in the American Journal of Clinical Nutrition, is that "vitamin D2 should not be regarded as a nutrient suitable for supplementation or fortification".
And with that in mind, let's take a look at the issue of contradictory studies that the IOM report focuses on.
Vitamin D studies are contradictory and flawed?
After reviewing nearly 1,000 published studies along with testimony from scientists and others, the experts on the IOM committee concluded that vitamin D does indeed play an important role in creating and maintaining strong bones. However, the committee also concluded that while further research was warranted into vitamin D's role in other health issues, at this point the evidence is mixed and inconclusive. Or to quote from the study:
"While preliminary evidence, usually from mechanistic studies, experimental animal studies, and observational studies in humans, can generate exciting new hypotheses about nutrient--health relationships, evidence from these studies has limitations. For instance, even in well-designed, large-scale observational studies, it is difficult to isolate the effects of a single nutrient under investigation from the confounding effects of other nutrients and from non-nutrient factors.
"Outcomes related to cancer/neoplasms, cardiovascular disease and hypertension, diabetes and metabolic syndrome, falls and physical performance, immune functioning and autoimmune disorders, infections, neuropsychological functioning, and preeclampsia could not be linked reliably with calcium or vitamin D intake and were often conflicting. Although data related to cancer risk and vitamin D are potentially of interest, a relationship between cancer incidence and vitamin D (or calcium) nutriture is not adequately and causally demonstrated at present; indeed, for some cancers, there appears to be an increase in incidence associated with higher serum 25-hydroxyvitamin D (25OHD) concentrations or higher vitamin D intake."
But let's take another look at these "conflicting" vitamin D studies that the committee referred to -- this time separating the studies into two different piles: those conducted with vitamin D2 and those conducted with D3. Voila! Suddenly, the studies would most likely exhibit stunning consistency -- those conducted with D2 providing only marginal benefits (except for bone health and rickets), whereas those conducted with D3 would most likely produce significant, consistent benefits across a wide spectrum of conditions. And those conducted with D3 produced in the skin by exposure to the sun would most likely produce the biggest benefits of all. And in fact, a broad reading of the available literature is strongly supportive of these conclusions.
Now to be fair, the committee did point out that nailing down conclusive evidence about any health benefits associated with a specific nutrient in regard to a specific disease is extremely difficult because of the difficulty in isolating the effects of a single nutrient under investigation from the confounding effects of other nutrients and non-nutrient factors. But this does not negate the results of vitamin D3 studies which strongly suggest the health benefits of D3 supplementation. On the contrary, it merely speaks to the need for additional studies combined with a different way of looking at the data. Or to look at it another way, would you refuse to bring an umbrella if the weatherman said there was only an 80% chance of rain? Would you refuse to act until he said the odds were 100%?
Most Americans are already maintaining desirable levels of Vitamin D?
The IOM expressed "surprise" when it concluded that a majority of North Americans are meeting their needs for vitamin D, based on the IOM's determination of optimal blood levels of 25OHD needed to support calcium absorption and bone health. The IOM hypothesized that this surprise is likely due to food fortification, the increased use of supplements, and the body's ability to synthesize vitamin D from sun exposure. All well and good, except for three key issues:
- Which 250HD levels are they measuring: D2 or D3? As we've already learned, D2 provides only 1/3 the potency at equivalent levels. This is crucial in that one of the largest sources of supplemental vitamin D in the average diet is vitamin D fortified milk. And yes, milk is fortified with D2, not D3.
- Who's getting sun exposure in North America? Thanks to skin cancer scare mongering, everyone is covering up and using high SPF sunscreens. In fact, sunscreen is now a common addition to skin moisturizers and even makeup.
- But more significantly, the IOM guidelines stand in stark contrast to overwhelming scientific evidence that confirms the significant medical benefits of higher vitamin D levels. How high are we talking about? 50 to 100 nmol/L minimum, with some experts recommending as high as 250 -- and that's D3 based, not D2.
That supplemental vitamin D above 600- 800 IU is inherently unsafe?
The logic the committee used to reach their conclusions concerning the upper safe levels for vitamin D supplementation is a masterpiece of sophistry.
"The ULs for vitamin D were especially challenging because available data have focused on very high levels of intake that cause intoxication and little is known about the effects of chronic excess intake at lower levels."
Then again, they could just as easily have said that "little is known about the effects of long term chronic insufficiency" -- which is, in fact, the very essence of their mandate.
"The committee examined the existing data and followed an approach that would maximize public health protection. The observation that 10,000 IU (250 μg) of vitamin D per day was not associated with classic toxicity served as the starting point for adults."
Note: the committee clearly states that daily intake of 10,000 IU of vitamin D per day has not been associated with any form of classic toxicity. Further, according to the American Journal of Clinical Nutrition, one can take 10,000 IU of supplemental vitamin D every day, month after month safely, with no evidence of adverse effect. Unless you are hyper-sensitive, you must consume 50,000 IU a day for several months before hypercalcemia (the initial manifestation of vitamin D toxicity) might occur.
"This value was corrected for uncertainty by taking into consideration emerging data on adverse outcomes (e.g., all-cause mortality) which appeared to present at intakes lower than those associated with classic toxicity and at serum 25OHD concentrations previously considered to be at the high end of physiological values."
So, they dropped the 10,000 IU by a factor of 16 to account for uncertainty??!! And are they talking about emerging data based on D2 or D3 supplementation? They certainly aren't talking about D3 production in the skin -- considering that a light-skinned person will synthesize 20,000 IU of vitamin D in as little as 20 minutes sunbathing on a beach.
The committee's recommendations for the new DRI's for vitamin D are absurdly low. They ignore the fundamental differences between vitamin D2 and D3. And because they ignore those differences:
- Their analysis of existing data is totally flawed
- Their assessment of optimal 25OHD serum levels is based on fantasy and flies in the face of mounting scientific evidence.
- And their caution on maximum safe levels of supplementation rests on mind boggling logic.
There is nothing in the committee's analysis to convince me to change my recommendations for vitamin D. These are:
- Get daily, direct sunshine for 10 to 20 minutes, and make sure you don't completely cover your body whenever you're outside. And keep in mind that wearing sunscreen pretty much kills the ability of your skin to produce vitamin D from sunlight -- meaning, the more you cover up and/or use sunscreen, the more you need to supplement.
- Lose weight, as vitamin D deficiency is more prevalent among overweight people.
- Supplement with 1,000 to 2,000 IU of vitamin D3 daily. It's quite difficult to get enough of the vitamin from food sources, and it's difficult to overdose on vitamin D at these levels.