On March 12, Dr. F. Perry Wilson delivered a lecture entitled "Vitamin D Supplements: A Double-Edged Sword?" on the medical site "Medscape." The presentation was spurred by the long-term results of a comparative study on the consumption of "Calcium/Vitamin D (CaD) supplements" by women for the prevention of bone fractures and osteoporosis, as well as colon cancer. This involved taking pills containing 1000 mg of calcium carbonate with 400 international units of vitamin D, compared to taking a placebo.

The study, published in the "Annals of Internal Medicine" on March 12, 2024, under the title: "The Long-term Effect of Randomized Calcium and Vitamin D Supplement Intake on Health in Older Women," provided critical insights.

Dr. Wilson, an Associate Professor of Medicine (Nephrology) and Public Health (Epidemiology of Chronic Diseases) at Yale School of Medicine, is also the creator of the popular online course "Understanding Medical Research: Your Facebook Friend is Wrong," and author of "How Medicine Works and When It Doesn't: Finding Trustworthy Health Information and Staying Healthy." He emphasizes the importance of seeking accurate and beneficial medical information for preserving health and preventing illnesses.

Medical Follow-up Analysis

The backdrop to this recent study, which is a “post-hoc” analysis of long-term medical follow-ups within the "Women's Health Initiative (WHI Study)" supported and funded by the "National Institutes of Health (NIH)" since 1991 across 40 medical centers in the United States, involves more than 36,000 postmenopausal women (aged between 50 and 79 years at the start of the study) consuming calcium and vitamin D supplements.

Initially hypothesized in the 1990s that women taking a combination of calcium and vitamin D would have a reduced risk of hip fractures and other fractures, along with lower incidences of breast, colon, and rectal cancers, the initial results, released after seven years into the study, noted a "slight" improvement in hip bone density but no significant decrease in hip fractures. Additionally, there was no effect on the incidence of colon and rectal cancer or breast cancer but an observed increase in the risk of kidney stones.

Dr. Cynthia Thomson, from the "Mel and Enid Zuckerman School of Public Health" at the University of Arizona, and her colleagues conducted this "post-hoc" analysis, which focused on two outcomes hinted at but not statistically confirmed in other vitamin D and calcium studies: a reduction in cancer risk and a possible increase in heart disease risk.

The new study's results (after long-term follow-up since 1991) revealed a 7% reduction in cancer incidences, with a parallel and equal increase in heart disease occurrences. The researchers summarized, "Calcium and vitamin D supplements appear to reduce cancer deaths and increase cardiovascular deaths after more than 20 years of postmenopausal women's follow-up, without any positive effect on deaths from all causes."

Varied Results of Supplements

In his presentation, Dr. Wilson began by saying, "In all clinical research, I believe there is no molecule with stronger associative data and weaker causative data than (the case of taking) vitamin D supplements." He cited low blood levels of vitamin D linked to increased risks of heart disease, cancer, falls, COVID, dementia, and more. However, randomized trials on vitamin D supplementation, which could prove a causative link to these outcomes, often yield negative results.

He highlighted a potential shift toward viewing normal vitamin D levels as an indicator of a person's healthy lifestyle factors, such as regular exercise, outdoor activities, and a balanced diet rather than the supplement intake itself.

Concluding Remarks

The Mayo Clinic summarizes that while calcium is critical for bone and cardiovascular health, vitamin D is essential for the body to absorb calcium. While food remains the best source for calcium and vitamin D, supplements may be necessary in specific situations where dietary intake is insufficient. However, the healthcare community emphasizes moderation and the potential risks of excessive supplementation, highlighting the importance of consulting healthcare professionals for personalized advice.