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.
This blog presents opinions and ideas and is intended to provide helpful general information. I am not engaged in rendering advice or services to the individual reader. The ideas, procedures and suggestions in that are presented are not in any way a substitute for the advice and care of the reader’s own physician or other medical professional based on the reader’s own individual conditions, symptoms or concerns. If the reader needs personal medical, health, dietary, exercise or other assistance or advice the reader should consult a physician and/or other qualified health professionals. The author specifically disclaims all responsibility for any injury, damage or loss that the reader may incur as a direct or indirect consequence of following any directions or suggestions given in this blog or participating in any programs described in this blog or in the book, The Building Blocks of Health––How to Optimize Your Health with a Lifestyle Checklist (available in print or downloaded at Amazon, Apple, Barnes and Noble and elsewhere). Copyright 2021 by J. Joseph Speidel