Safe Supplementation of Vitamin D

This study, which recommends people to consume three times more vitamin D than the Institute recommended in 1997, also concludes that consuming more vitamin D could be hazardous. The flaw in the report is its structure which flows through to its conclusions.  The Institute only considered large randomized controlled trials or large cohort trials.  Observational trials and case control trials, which represent the large majority of studies, were excluded.  The Institute also failed to exclude randomized trials that were flawed. In addition, even when a small component of a large trial demonstrated a positive effect from vitamin D, the report only discussed the whole trial as if the focused study did not exist.  Much of the commentary concentrated on vitamin D deficiency causing disease, rather than vitamin D sufficiency preventing disease.

Nonetheless, they could not exclude information from major studies that demonstrate the effectiveness of vitamin D.  On page 122 (of 981 pages) of the report, the Institute cites the Framingham Offspring Study, which clearly demonstrated declining rates of cardiovascular disease as levels of vitamin D rose to 70 ng/mL. They also failed to include subsets of data from the largest survey of nutrition in the US, which has the acronym NHANES (The National Health and Nutrition Examination Survey), and is repeated periodically (NHANES I, NHANES II etc). NHANES I, published in 1988, was responsible for noting the relationship were patients with higher vitamin D consumption had lower rates of breast cancer. This result has been confirmed in other studies. The benefit of vitamin D above 70 ng/mL has not been demonstrated so I don’t recommend it; the last case of vitamin D toxicity reported to the US Poison Control Centers had a level well over 100 (actually 482!). In terms of harm, almost every study showing harm involved the simultaneous administration of calcium with vitamin D.  Excessive calcium administration is bad for you, even without vitamin D.

I reviewed my library of 46 original publications ranging from the American Journal of Clinical Nutrition to the New England Journal of Medicine.  I found well-done studies which indicate vitamin D’s association with reductions in cardiovascular disease, cancer, diabetes, and it certainly makes for stronger bones.

James Katz MD

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