• A new study finds fish oil supplements may help reduce the risk of a cardiovascular event like a heart attack.
• Vitamin D supplements appeared not to reduce heart attack risk, but did reduce risk of cancer development.
• The authors say eating fish rather than taking a supplement may be just as effective.

Cancer and heart disease are the two leading causes of death in middle-aged adults, according to a 2017 reportTrusted Source by the Centers for Disease Control and Prevention (CDC).

However, a study called the Vitamin D and Omega-3 Trial (VITAL) finds that both vitamin D and fish oil may play an important role in reducing mortality from these diseases.

The results will be presented this week at the North American Menopause Society (NAMS) Annual Meeting in Chicago.

Fish oil long associated with reduced cardiovascular disease risk

VITAL is an ongoing research study of about 26,000 American men and women. It’s investigating whether taking daily dietary supplements of vitamin D-3 (2,000 IU) or omega-3 fatty acids reduces the risk for developing cancer and cardiovascular disease (CVD) in people without a history of these conditions.

“Fish oils have long been believed to be beneficial in the prevention of CVD. This is based on the principles of the Mediterranean diet which is high in certain fatty fish, such as salmon and mackerel, and nuts which contain unsaturated fatty acids, specifically omega-3 fatty acids,” said Dr. Sreenivas Gudimetla, a cardiologist at Texas Health Fort Worth and Texas Health Physicians Group, who isn’t associated with this study.

Researchers found that participants taking omega-3 fatty acid supplements (fish oil) had a significantly reduced risk of heart attack. Findings also indicate the largest benefit was in people who ate less than 1.5 servings of fish per week.

“I think we’re finally coming to some conclusions about vitamin D and omega-3 supplements, but I do want to say it’s not a ‘one-size-fits-all’ answer. People have to understand that some people are more likely to benefit than others and if they have low fish consumption they’re more likely to benefit from the omega-3s in fish oil,” Dr. JoAnn Manson, director of the VITAL trial, Professor of Medicine at Harvard Medical School, and Chief of Preventive Medicine at Brigham and Women’s Hospital in Boston, told Healthline.

Vitamin D: No effect on heart but reduced cancer deaths

While vitamin D supplements didn’t reduce major CVD events or the incidence of cancer, it was associated with a significant reduction in total cancer mortality among people in the trial for at least 2 years.

“No vitamins can prevent the development of heart disease, so it’s important to reduce other risk factors such as cholesterol, smoking, hypertension, and diabetes,” said Dr. Brandie Williams, a cardiologist at Texas Health Stephenville and Texas Health Physicians Group.

But for those who took a vitamin D supplement and did develop cancer, the death rate from cancer was 25 percent lower, according to the trial’s findings. Researchers confirmed this effect of reduced cancer death through recent meta-analyses of previous vitamin D trials.

Overweight saw no benefit, moderate intake is best

Manson said that, while vitamin D was associated with a 25 percent reduction in cancer mortality, this benefit was only seen in those of average body weight, and not the participants with overweight or obesity.

“For vitamin D supplementation, we’re recommending that more research be done on this cancer death reduction to understand it better. We think the longer term follow up of the VITAL trial will be critical,” said Manson.

She cautioned that at this point, she’s not recommending a change in the guidelines for vitamin D but there isn’t any clear safety concern with moderate intake of about 2,000 IU per day.

“Those who are already taking vitamin D supplements may continue to do so as long as they’re not taking megadoses, doses well above what’s currently considered safe — up to 4,000 IU a day.”

More research needed

She emphasized that further research is needed to discover exactly what population will derive the greatest benefit from supplementation.

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This pattern suggests a complex balance of benefits and risks for each intervention and points to the need for additional research to determine who is most likely to benefit from these supplements,” said Manson. “So what we’re saying at this point in terms of the takeaway is that for fish oil, it’s not a population-wide recommendation to take it.”

“Generally, we’re advising increased fish consumption to at least two servings per week, but in people who don’t eat fish because they don’t like it or are allergic — they could use algae-based omega-3 supplements,” said Manson.

However, she recommended that people talk to their healthcare provider first about whether an omega-3 fish oil supplement might benefit them “especially if they have risk factors for heart disease.”

The bottom line

A recent clinical trial finds that fish oil supplements can reduce cardiovascular disease risk and vitamin D significantly reduces cancer mortality. Participants with overweight or obesity taking vitamin D didn’t see any cancer benefit.

The findings don’t mean everyone should begin taking vitamin D and fish oil supplements to cut their risk of heart disease and cancer. People should first speak with their healthcare provider to find out if fish oil is right for them.

However, those already taking a vitamin D supplement should be fine as long as they don’t take over 4,000 IU of the vitamin per day.