VITAMIN D SOURCES, Part 3: Supplements

Our previous blogs about vitamin D sources explained the advantages of sun, along with some warnings; food options, with a caveat about mercury in fish; and the wrong form of vitamin D in most fortified foods. Now, let’s have a close look at manufactured vitamin D supplements.

Vitamin D Supplements

A recent review of studies on vitamin D revealed that ordinary doses of vitamin D supplements may well be linked to reductions in mortality from life-threatening conditions such as cancer, cardiovascular disease, and diabetes mellitus. These diseases account for over 60% of deaths in developed countries.

So what does that mean for you (and us)?

First, it means you should take supplementation seriously, especially if tests have shown you are VDD (vitamin D deficient). However, you should be prudent in your response and become familiar with the contents of vitamin D supplements.

Know that there are two basic kinds of vitamin D supplements: D2 and D3. Many retailers will sell you D2, but for the reasons we provided in the previous blog (Vitamin D Sources, Part 2: Food) D2 is not as bioavailable (does not absorb well) as the D3 form.

So if you are going to supplement because you are VDD, and sun and food just won’t do it for you, make sure you read the labels and demand D3.

Vitamin D Toxicity

Second, you should be aware of the debate about toxicity—how much vitamin D from supplements is too much? We have read what seems like an uncountable number of studies, abstracts, reviews, and opinions on the matter. Government agencies seem to take the conservative stand, suggesting a daily range between 400 –2000 IUs. Independent alternative health practitioners tend to proclaim there is no credible evidence that we can take too much vitamin D, recommending between 4,000 – 10,000 IUs per day. And there are those who recommend much more.

The arguments for the higher doses are based on the observation that a few minutes in the sun will result in anywhere between 10,000 – 50,000 IUs all at once, with no symptoms of toxicity.

Indeed, R. Vieth, of the University of Toronto, has found no evidence of toxicity using supplement doses of 10,000 IUs/day. He suggests toxicity probably begins after consistent intake of 40,000 IUs/day.

We invite you to read, talk with a credible health care practitioner with a background in nutrition, and to assess your personal vulnerability to the high-risk diseases before you decide on whether and how much to supplement. And we recommend you be monitored by health care providers if you take very high doses for any reason.

You can reach Gloria Askew, RRN and Jerre Paquette, Ph.D at

You can read more about Gloria and Jerre’s book, Secrets of Supplements: The Good, the Bad, the Totally Terrific, here.

You can read other bloggers here.


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