Clearing Up Confusion About Vitamin D and Fish Oil Supplements

Clearing Up Confusion About Vitamin D and Fish Oil Supplements

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By Dr. Lisa Larkin, MD, FACP, NCMP, IF


More and more Americans turn to vitamins and supplements for a number of health conditions. In the U.S., these over-the-counter dietary supplements are not regulated by the FDA, and thus are not held to the same evidence-based, safety and promotional claims standards of prescription medications.  For consumers, it can be confusing and difficult to know if and which supplements may be beneficial for them.

Fortunately, a landmark study has recently been published that provides more clarity around the benefits of fish oil and Vitamin D when it comes to reducing the risk of cardiovascular events and cancer.

The VITAL study was funded by the National Institutes of Health and many of its findings were recently published in the New England Journal of Medicine. It is an important study as it is one of the first to look at men and women who are considered at average risk for heart disease and cancer (meaning those who have not previously had a heart attack, stroke or cancer other than skin cancer). The study is large – nearly 26,000 patients, equally stratified between men (age 50 and older) and women (age 55 and older), and is a racially diverse study, designed to investigate whether taking daily dietary supplements of vitamin D (2000 IU) or omega-3 fatty acids (fish oil supplements, 1 gram) reduces the risk for developing cancer, heart disease, and stroke.


First, there is great data showing that a healthy diet including fish (at least 1 – 2 servings per week) does have heart benefits including a decrease in cardiovascular disease. Researchers, of course, want to know if fish oil supplements can produce the same benefits as omega-3 fatty acids found in fish.

Unfortunately, the data showed only an 8% reduction of cardiovascular events across the entire population – which did not meet statistical significance. However, the VITAL study did look at individuals who consume very little fish in their diet (less than 1.5 servings per week), and for that population, fish oil supplements did show benefit in reduction of cardiovascular events (19%) including a 40% reduction in heart attack.

Additionally, the data also showed that there was a reduction in cardiovascular events for African Americans, specifically heart attacks.


Nearly 60% of the adult US population has suboptimal levels of Vitamin D. Fatty fish and fortified foods, such as milk, cereal and some orange juices are the primary sources of Vitamin D through diet, and so it is difficult to get enough Vitamin D through diet alone.

The VITAL study examined cardiovascular disease and cancer prevention. After 5.3 years, there was no significant reduction for those in the Vitamin D group.

However, Vitamin D is essential for the absorption of calcium and thus is very important for bone health. Studies have found that vitamin D with supplemental calcium can reduce the rate of postmenopausal bone loss, and is associated with significant reductions in the risk of hip and non-vertebral fractures.