Interview with Dr. William Davis on the IOM Recommendations for Calcium and D


We would like to welcome Dr. William Davis. We'll be discussing the recent Institute of Medicines recommendations on calcium and vitamin D for good bone health.

Dr. William Davis' Bio:

Dr. Davis is founder of the online heart disease prevention and reversal program, His ongoing discussions are hosted on his blog, The Heart Scan Blog.   His new book, Wheat Belly, is scheduled for release this fall by Rodale.

Dr. Davis, as you know, the Institute of Medicine (IOM) recently released new recommendations for calcium and vitamin D, and we'd like to ask you about this to clear up some misconceptions the members have about their current intake of these supplements.

Dr. Davis, could you start by explaining the new guidelines and your opinion on the Recommended Daily Allowance (RDA) on calcium and D that the Institute mentions?

The IOM was charged with a difficult job: Develop guidelines for vitamin D intake that suit everyone from newborns, to pregnant mothers, to the elderly, slender or overweight, from_ Maine to Hawaii_. Given the wide range of sun exposure, genetic variation, and body size, they tried to develop advice that meets all needs.

After they reviewed the existing literature, they came to several conclusions:

  1. That the Recommended Dietary Allowance (RDA) for vitamin D from 1 year of age on up to adults is 600 units per day.

  2. The blood level of 25-hydroxy vitamin D, the widely-used measure of vitamin D adequacy, that should be attained by this RDA is 20

  3. The vitamin D safe Upper Limit (UL) for adults is 4000 units per day.

  4. For calcium, the RDA is 1000 mg for both adult males and females, increasing to 1200 mg per day at age 51 for females, age 71 for males.

For vitamin D, this represents a shift upward in RDA and especially the UL, based on published observations of widespread deficiency and lack of documented toxicity.

My opinion of the IOM's final recommendations is that I essentially lump them together with the opinions of other "official" agencies: While well-intended, the necessarily conservative views of such committees make them woefully behind the times.

For one, they have an impossible job that has no possible solution. A guideline for intake that suits the needs of all Americans cannot be created because needs are so widely variable. It varies among races, body sizes, genetic factors, and a whole host of other reasons.

Two, the nature of their task was to be strict in interpretation of data. They could not introduce the excitement of new and interesting findings, emerging science, or novel observation. They had to rely on hard data, similar to that required for approval of a drug. The problem: Vitamin D is not a drug and does not have drug-like research behind it.

Three, the committee members were not vitamin D experts, but volunteer physicians and scientists with some background in calcium and vitamin D. To their credit, the committee members consulted with the national vitamin D experts, many of whom have been publishing their data for two decades. Oddly, the opinions of the vitamin D experts, widely known and publicized, were apparently not incorporated into the guidelines.

I therefore regard the IOM's advice on vitamin D and calcium as just the sort of extremely conservative, one-size-fits-all analysis that such efforts tend to generate. Having addressed vitamin D issues in literally thousands of patients and witnessing the results, I will give as much weight to the IOM's guidelines as I do to the FDA's Food Pyramid advice on diet: I ignore their advice because I feel it is wrong and unnecessarily dogmatic and conservative.

In my view, it would have been just fine to simply say something like, "The data are compelling and promising, but are incomplete. In particular, epidemiologic data suggest that vitamin D deficiency is potentially widespread with implications for increased risk for cardiovascular disease, cancer (especially breast, colon, and prostate), and bone health. However, we lack sufficient treatment data and outcome studies that justify reaching broad conclusions sufficient to draft national health policy. In the meantime, every American's vitamin D status is an individual matter."

Sadly, they said nothing of the sort. Most surprisingly of all, some of the committee members, despite their measured comments in the official report, in media interviews made inflammatory and, I believe, unfounded accusations, including outright silly comments that suggest that the entire vitamin D phenomenon is nothing more than the supplement industry trying to make money. This, of course, is absurd.

I know from personal experience, that the amount of D3 I take is determined by a 25-hydroxy vitamin D test, not from the IOM's recommendations. Shouldn't we base our intake on this test, since it will tell us if we are deficient in D or not, which could alter the amount you need to take?

Also, many individuals like to get D3 from the sun; is it possible to get adequate amounts of D3 from the sun, as we age?


Trying to draft a one-size-fits-all from infancy to adulthood, across all races, body sizes, and genetics is like making all Americans try to wear one size pair of pants. It just cannot work.

To achieve the very same blood level of 25-hydroxy vitamin D, the dose range can be as wide as 20-fold, i.e., one person can require as much as 20-times more than another person to achieve the same blood level. For instance, someone taking 1000 units of vitamin D may have a 25-hydroxy vitamin D level of 55 ng/ml, while another person may require 12,000 units per day to achieve the very same level. Declaring both people to have identical requirements makes no sense.

The same applies to sun exposure. Amount of time, sun intensity, latitude, altitude, skin surface area exposed, and skin color are just a few of the variables that can affect vitamin D activation from sun exposure. On top of this, the older we get, the less vitamin D is activated, such that people over age 40 are capable of only modest degrees of vitamin D activation even in summertime.

For this reason, it is my view that establishing vitamin D needs is not the charge of the IOM, but of an individual's healthcare that should remain an issue between the individual and his or her healthcare provider. For me, this means I will continue to advise patients to achieve 25-hydroxy vitamin D levels of 60-70 ng/ml, the range at which I witness incredible health benefits.

For those who weren't able to read the IOM recommendations on vitamin D and calcium, we'll continue with some basic questions on both of these supplements.

Do you believe that the labs have the reference range for normal D values set too low at 30 ng/ml; and what would you like it to be?

Why is vitamin D vital to our bone health and health in general?

The data telling us what level of 25-hydroxy vitamin D is desirable are limited primarily to epidemiologic observations. Several large studies have shown that a 25-hydroxy vitamin D level of 30 ng/ml is associated with substantially fewer cardiovascular events and mortality, cancer mortality, and all-cause mortality compared to 15 ng/ml. Unfortunately, we have inadequate data that probe levels higher than 30 ng/ml. We certainly do not know where the potential benefits of vitamin D are maximized.

Having managed vitamin D supplementation in several thousand patients, however, my anecdotal observation is that benefits plateau at around 60 ng/ml, i.e., there appear to be no additional incremental benefit above this level. There is virtually zero downside of this approach.

We need prospective confirmation of such anecdotal observations. But the benefits I have witnessed, such as increased bone density, relief from arthritis, accelerated bone healing after fracture; increased HDL cholesterol, reduced triglycerides, reduced blood glucose, reduced inflammatory measures like c-reactive protein; relief from winter "blues;" clearer mentation and memory; and marked reduction in viral illnesses have convinced me that the effects of vitamin D supplementation are far greater than suggested by the conservative analysis of the IOM.

Do you feel the IOM's recommendations for calcium are set too high for most individuals?

I know many who feel that they should get at least 1,200-1,500 mg of calcium a day from all sources (food/supplements) regardless of their D score; so I'm wondering what your thoughts are on this?

This is yet another issue in which I differ with the IOM committee opinion. Provided vitamin D has been restored to higher levels, e.g., 60 ng/ml 25-hydroxy vitamin D level, then calcium intake is not an issue for health. Let me explain.

The data suggesting that calcium intake is essential for bone and other health originated from studies in which full vitamin D restoration was not undertaken. Vitamin D doses of 400 to 800 units per day were used, not uncommonly the relatively ineffective D2 or ergocalciferol form or poorly absorbed tablets. When vitamin D is not restored, then higher intakes of calcium may provide small benefits.

However, when vitamin D is fully restored, intestinal absorption of calcium is doubled. Calcium intake is no longer the limiting factor. In fact, supplemental calcium may actually be undesirable, since too much calcium can be absorbed, leading to abnormally high blood calcium levels and kidney stones.

I believe that we need to start from scratch in our analysis of what humans need in the way of calcium when vitamin D has been fully restored. Until then, I tell my patients to take no more than 500 mg per day of supplemental calcium if they take any calcium at all, since some recent data suggest that cardiovascular events like heart attack may be increased above this level.

How much D3 do you recommend to your patients? Do you base this on their medical history and 25-hydroxy vitamin D test scores, or is the recommendation the same for all?

For our uninsured members would you recommend the mail order blood spot testing, and do you think it's accurate in determining vitamin D levels?

The only confident means to determine an individual's need for vitamin D, given the enormous variation, is to be guided by 25-hydroxy vitamin D blood levels. Using 60-70 ng/ml as a target, doses in my clinic range from 0 units per day (rare) to over 20,000 units per day. The majority of adult men and women, however, require around 4000-8000 units per day to achieve this level.

I advise patients to take only the D3 or cholecalciferol form, the form recognized by the body as the human form, not the plant or invertebrate D2 form. The D3 form is best taken as gelcaps or drops to ensure absorption, since tablets are poorly or erratically absorbed. The D2 is available as tablets over-the-counter or as the prescription form; emerging data suggest D2 is inferior, not surprising given that it is not the human form.

For patients who do not have access to vitamin D testing, accurate and relatively inexpensive fingerstick 25-hydroxy vitamin D testing is available. I have used these test kits many times and have found their information to be credible and consistent with standard blood draw values.

Closing comment: Admittedly, we still need plenty of data validating how to best accomplish vitamin D restoration. However, having restored vitamin D in thousands of patients, I have no lingering doubt: Vitamin D is, without a doubt, the most incredible "nutrient" issue I have ever seen, with benefits from restoration far exceeding anything I ever expected.

My personal experience with vitamin D is similar to that of my patients: Near-elimination of viral illnesses like flu, improved well-being (substantial), reduced blood sugar, greater energy and clarity. I shudder to remember how I often felt, especially during the long winter months. In my mind, there is no turning back. While the IOM's two-steps-forward, one-step-back comments did indeed advance the broad acknowledgement of vitamin D's health potential, I am confident that emerging studies will bear out the health transformations that I witness every day.

On behalf of members and readers, we'd like to thank Dr. William Davis for a very informative interview on the IOM's recommendations for vitamin D and calcium, for good bone health.