Most people do not need extra vitamin D

Overall, nearly one in five U.S. adults are now taking vitamin D. There is evidence
that a substantial proportion of U.S. adults are taking too much. If supplemental
vitamin D is needed, the Recommended Dietary Allowance (RDA) for vitamin D
appears as micrograms (mcg) of cholecalciferol (vitamin D3). From age 9 to age
70, the RDA is set at 600 IU (15 mcg/day), and for adults, over age 70 years, the
RDA is 800 IU (20 mcg/day). Multivitamins typically contain about 400 IU/day.
The tolerable upper limit is 4000 IU/day; beyond this level risk of toxic effects increases.

National Health and Nutrition Examination Surveys (NHANES) indicate that in 2013-2014 an estimated 6.6% of people age 60 and older were taking at least 4,000 IU of vitamin D daily, as were 4.2% of all women. High doses of vitamin D
are associated with an increased risk of side effects, particularly when taken with
calcium supplements. Some epidemiologic studies suggest high doses of vitamin D
may be associated with increased risk of prostate and pancreatic cancers, and deaths
from all causes.

So, what can we conclude about vitamin D? According to a 2019 editorial in the
JAMA, “Multiple trials have failed to demonstrate significant benefits of vitamin D
supplementation….High-dose monthly oral vitamin D3, compared with placebo,
did not reduce risk of incident cardiovascular disease or death. In the Vitamin D
and Type 2 Diabetes (D2d) trial, vitamin D supplementation, compared with placebo,
failed to lower risk of incident type 2 diabetes in patients with prediabetes.”90
Research is underway that may reveal benefits from supplementation, but so far,
studies have found that most people do not need extra vitamin D.

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