Mega-study: Omega-3s, folic acid, CoQ10 benefit heart, but beware of beta carotene

Dec. 5 (UPI) -- Instead of singling out vitamins and minerals that may help heart health, researchers hope their comprehensive review of many studies will pave the way for clinical trials to identify the best mix of micronutrients to supplement people's diets -- since not all are beneficial and some, like beta carotene, may cause harm.

That's the gist of a major analysis, published Monday in the Journal of the American College of Cardiology, by researchers from the United States and China.

Scientists said they developed "evidence-based maps" from summarizing 256 meta-analyses of randomized, controlled trials on micronutrients taken as dietary supplements.

These studies explored the effects of a wide variety of micronutrients on blood pressure, blood lipids, blood glucose, deaths from any cause, cardiovascular disease risks, and Type 2 diabetes risk.

After examining 27 different types of antioxidant supplements from 884 studies, involving 800,000-plus patients, the researchers said they found strong evidence that several offered cardiovascular benefit.

These included omega-3 fatty acid, which decreased mortality from cardiovascular disease; folic acid, which lowered stroke risk; and co-enzyme Q10, or CoQ10, which decreased death from all causes.

But Vitamins C, D and E, and selenium showed no effect on long-term cardiovascular disease outcomes or reducing Type 2 diabetes risk, according to the scientists' review.

Beta carotene supplements moderately increased the risk of heart attack and Type 2 diabetes, and, to a lesser extent, all-cause mortality, cardiovascular disease death and stroke risk, the investigators said.

Separately, in June, the U.S. Preventive Services Task Force issued a recommendation statement specifically warning people not to take beta-carotene or vitamin E to prevent heart disease, stroke or cancer.

Taking beta-carotene for this purpose increases the risk of lung cancer in people already at risk, the authoritative panel of experts had said, citing the latest available scientific evidence.

Healthy diets are rich in antioxidants like amino acids, omega-3 fatty acids and vitamin C, but exactly how beneficial these micronutrients are for cardiovascular health has long been controversial, according to a news release.

The scientists said they anticipate their analysis will offer more clarity, and they pointed to the need for "more personalized, precision-based" dietary interventions.

"For the first time, we developed a comprehensive, evidence-based integrative map to characterize and quantify micronutrient supplements' potential effects on cardiometabolic outcomes," Dr. Simin Liu, a principal investigator of the study and professor of epidemiology and medicine at Brown University, said in the release.

Liu, a physician-scientist and epidemiologist, said the study "highlights the importance of micronutrient diversity and the balance of health benefits and risks."

He said the findings could be used to set the stage for large clinical trials to study specific combinations of micronutrients and their impact on cardiovascular health.

Supplementing a person's diet with antioxidants has long been thought to play a role in heart health because these nutrients work to reduce oxidative stress, which is a known contributor to many cardiovascular diseases, the release said.

And heart-healthy diets like the Mediterranean diet and the Dietary Approach to Stop Hypertension, or DASH, feature foods that are naturally rich in antioxidants.

But results have been inconsistent from previous studies of antioxidant supplements and the approach has not been widely adopted in preventative cardiology.

Liu pointed out that previous research on micronutrient supplementation has mainly focused on the health effects of a single or a few vitamins and minerals.

So, with the new study, Liu said: "We decided to take a comprehensive and systematic approach to evaluate all the publicly available and accessible studies reporting all micronutrients, including phytochemicals and antioxidant supplements and their effects on cardiovascular risk factors as well as multiple cardiovascular diseases."

Over a follow-up period averaging three years, there were 27,823 deaths from all causes; 15,593 heart disease deaths; 11,202 myocardial infarctions; 8,276 strokes; 2,656 cases of coronary heart disease, and 409 instances of heart arrhythmias recorded among the roughly 800,000 participants across the numerous reviewed studies.

In terms of doses, CoQ10 supplementation, averaging 50 milligrams per day, reduced all-cause mortality in seven trials performed in heart failure patients, the investigators said.

Among the reviewed studies, a median dose of 1.8 grams/day of omega-3 fatty acid reduced the risks of cardiovascular disease death, heart attack and coronary heart disease, they said.

And folic acid supplementation, with a daily dose averaging 3 mg., reduced the risk of stroke.

By contrast, a median dose of 20 mg./day of beta carotene supplementation increased the risk of all-cause mortality, cardiovascular death and stroke, the scientists said.

The work was partly supported by the U.S. Fulbright Program, where Dr. Liu was a Fulbright Distinguished Chair in Global Health in 2019-20.

The research was also funded from Chinese sources, including the Beijing Advanced Innovation Center for Food Nutrition and Human Health and the National Natural Science Foundation of China.