Vitamin D RDA
An RDA (Recommended Dietary Allowance) is published for most essential nutrients by the US Institute of Medicine (IOM). In November 2010 they published a new report containing their revised estimates and recommendations for Vitamin D, including
- Adequate Intake Level (AI)
- Recommended Dietary Allowance (RDA)
- Tolerable Upper Intake Level (UL)
These are summarized below:
Official IOM Recommendations - 2010
Daily Vitamin D, in IUs
|> 70 Yrs||-||600||4000|
But does that make sense? Nature gives people different skin sizes after all, and larger skins will naturally make more vitamin D than smaller ones.
Why the IOM thinks 600 IU of Vitamin D is enough
It is hard to reconcile the newly published recommendations of the IOM with modern research on vitamin D. This research links low vitamin D with cancer, heart disease, diabetes, multiple sclerosis and many other major and minor diseases. The amount of vitamin D required to protect against these conditions is much greater than that required for protection against rickets and osteomalacia.
The IOM does not seem to take these new facts adequately into consideration, even though they now recommend 600 IU for younger adults, instead of their previous benchmark of 200 IU. That earlier recommendation remained in force for 13 years, even though it was quite inadequate.
But is this new RDA any more trustworthy? The main problem appears to be that the IOM targets a very low vitamin D blood level of 20 ng/ml , as indicated by their report Dietary Reference Intakes for Calcium and Vitamin D (page 8)
“Although serum 25OHD level cannot be considered a validated health outcome surrogate, it allowed comparison of intake or exposure with health outcomes. Newer data also allowed the simulation of a requirement distribution based on serum 25OHD concentrations. A level of 16 ng/mL was consistent with the intended nature of an average requirement, in that it reflects the desired level for a population median – it meets the needs of approximately half the population. Moreover, benefit for most in the population is associated with serum 25OHD levels of approximately 20 ng/mL, making this level a reasonable estimate for a value akin to “coverage” for nearly all the population. Available data were used to link specified serum levels of 25OHD with total intakes of vitamin D under conditions of minimal sun exposure in order to estimate Dietary Reference Intakes.”
This is what they may be trying to say: A vitamin D blood level of 16 ng/ml would be enough for half the population, but for nearly everyone to have enough, the level needs to be 20 ng/ml. From this we can estimate how much vitamin D people need to take, if they do not get much sunshine.
Not very convincing, is it? But if the IOM were right about 20 ng/ml being an appropriate target blood level, then 600 IU would be a reasonable vitamin D RDA for children and for some young adults. (Older people and heavier people would need more, on average.)
But is the IOM aiming at the right target?
Research indicates that 20 ng/ml is not enough
We believe that 50 ng/ml is a more appropriate vitamin D target level. This is a critical point, so let’s be very clear. The main reasons are:
- People whose vitamin D levels are above 40 ng/ml are less susceptible to a wide range of major and minor diseases than are people with vitamin D levels of 20 ng/ml, according to several medical and scientific studies.
- For many diseases (e.g. breast cancer, several other cancers, type 1 diabetes and multiple sclerosis) the improvement in disease incidence continues until vitamin D levels reach 50 ng/ml or higher. See chart Disease Incidence by Serum 25(OH)D.
- Many people who spend their days in sunlight (farmers, builders, hunters, field-workers, fishermen etc.) naturally maintain vitamin D blood levels of 50 to 80 ng/ml, without any supplementation. (Most of mankind and his ancestors have lived this way for millions of years.) See Dr Heaney’s paper “Vitamin D in Health and Disease”.
Unfortunate Consequences of the new Vitamin D RDA
Considering their silence on vitamin D for the past 13 years, the IOM’s latest recommendations are a disappointment.
Most medical doctors, nutritionists and dieticians are only vaguely aware of the latest vitamin D research, and don’t have time to put it all together. So they just rely on the recommendations of their medical institute.
Because of these new recommendations, those health professionals will continue to believe that vitamin D deficiency is a relatively rare condition, easily corrected by a small (and ineffective) dose of vitamin D.
This is most unfortunate for hundreds of millions of people around the world who are already suffering from the increased disease burden of chronic vitamin D deficiency – and may continue to do so.
Do we need a Vitamin D RDA?
In a way, it is a pity that the IOM has published a vitamin D RDA at all. It may encourage us to oversimply a complex issue.
Vitamin D is more of a hormone than a vitamin. With a hormone, the usual practice is first to establish the healthy range for blood levels, then to measure the individual’s blood level, to see how it compares. Only then can anyone decide how much of the hormone that person needs to take, if any.
To maintain a healthy vitamin D level of 50 ng/ml, different people may require anything from zero to 20,000 IU of oral vitamin D3 per day. If you set one RDA for everyone, wherever you set it will be wrong for most people!
Individual needs for oral vitamin D vary widely, and these variations cannot always be predicted, even when body mass and the amount of sunlight exposure is known. But it would help if the recommendation were linked to body mass–for example 60 IUs of vitamin D3 per kg of body mass– and also to a given level of sun exposure.
Are commercial or political issues influencing the vitamin D RDA?
At first glance, you might not think so. After all, vitamin D3 is a very inexpensive supplement, so there’s little money in it.
But cancer, heart disease and diabetes are all associated with vitamin D deficiency, together with dozens of other major and minor health challenges. The pharmaceutical and healthcare industries make billions of dollars from treating these diseases.
Their profits will remain high as long as people remain vitamin D deficient.
Shouldn’t the government protect us from corporate greed? They should, but in this instance they may not want to. Governments get huge tax revenues – and political parties receive massive campaign contributions – from wealthy pharmaceutical corporations. So why would governments (or even the opposition) want to jeopardise those funds?
And governments, despite what we would like to believe, may not wish for the people they serve to live longer.
To take a cynical view, governments’ financial interests are best served when you work longer (pay more tax) but die sooner (less pension to pay out).
So whose interests are being served by the IOM’s 2010 vitamin D RDA pronouncement? Not yours, gentle reader.
Expect a long wait for a new Vitamin D RDA
Although the IOM has failed to show the way, more-enlightened medical professionals, and some of the media are putting together the whole vitamin D story, and catching on to vitamin D’s full potential.
No doubt even the IOM will get there eventually. But you may not want to wait for them. They’ve only increased their recommended intake by 400 IU in the last 13 years. At this rate it would take them 143 more years to reach 5000 IU (an effective dose for many adults). Ho-hum.
In the meanwhile, none of us is getting any younger.
You need to decide for yourself about vitamin D supplementation. You will want your decision to be well-informed, and based on sound science and common sense, because optimum vitamin D is critically important for your health.
What is optimum for you? See How to Calculate Your Personal Vitamin D Dosage.