UA Researchers Discuss Vitamin D Supplementation Benefits and Risks


Researchers at the University of Arizona are attempting to weigh the risks and benefits of vitamin D supplementation, a debate that has continued for decades.

“Vitamin D is historically associated with calcium use and strengthening bones, but now it’s showing health benefits that 20 or 30 years ago health professionals dismissed because of lack of information,” says Dr. Ron Watson, University of Arizona Professor in Health Promotion Sciences Division of the Mel and Enid Zuckerman College of Public Health.

Watson was funded for 30 years by the Wallace Research Foundation to study dietary supplements in health promotion. He recently edited and published a handbook of vitamin D in human health.

“The main source of vitamin D is sunlight and we get very little from what we eat,” says Watson.



Although we live in a state that is sunny almost 365 days of the year, Watson says Arizonans have less vitamin D than what is recommended. Researchers are still puzzled by this, but point to increased precautions taken in states that are notorious for skin cancer or have consistently hot weather. People with darker skin also absorb less vitamin D from the sun because of the different amount of melanin in their skin.

The handbook provides the most current research about the benefits of vitamin D, which include improving musculoskeletal health, chronic disease, infectious disease, women’s health and even cancer.

Studies on the correlation between vitamin D and cancer have proved conflicting.

Watson says vitamin D has shown to decrease many types of cancers, but some say that it’s a two-edged sword.

“Supplements aren’t regulated like food and the best dose, if any dose is needed at all, is still being studied,” says Dr. Beth Jacobs, a UA cancer epidemiologist.

Jacobs has two grants to study the relationships between vitamin D and cancer. She is investigating the correlation between vitamin D and the incidence of polyps known as colorectal adenomas and the reoccurrence of breast cancer.

“Nutritionists believe there is a u-shaped curve, where being on either the low end or high end leads to adverse health outcomes, that’s why we advocate for moderation,” says Jacob.

But deficient is in the eye of the beholder, says Watson.

“A vitamin is something you don’t produce, you have to get it externally,” he says.

According to Jacobs, the problem lies in how people are being treated for their nutrient deficiencies.

“You have lumpers and splitters. The lumpers put all dietary patterns together and adjust accordingly, or the splitters identify each nutrient separately and treat it. Both have strengths,” says Jacobs.

Both agree that consulting a doctor is the first step to determining if a supplement is right for you. However there will be continued debate whether to get supplements, like vitamin D naturally from lifestyle changes or from a synthetic prescription.

The multi-billion dollar supplement industry is successful because half of Americans believe that taking supplements are harmless, Jacobs says in a co-authored commentary published in the Journal of the National Cancer Institute.

While recent studies have proposed that vitamin D plays a role in prevention of cancers, specifically breast, colorectal and prostate people have jumped on the bandwagon too soon, Jacobs says.

Researchers question the accuracy of observational studies and the limited data from clinical trials which link vitamin D supplementation to cancer reduction.

“Getting people to accept supplements is partly an education process and a public health policy process,” says Watson.

“Of course too much of anything is bad.”

A large cohort study part of the Women’s Health Initiative was conducted in July 2012 and studied the delicate balance of vitamin D supplementation.

There is a fuzzy line between supplementation that promotes cancer and that prevents cancer, according to a Jacobs.

“The strength of science is that we are consistently studying it and revising it,” says Jacobs.

“There is simply more research on vitamin D that must be done.”



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