Most vitamin, mineral supplements not shown to lower heart disease risk

Vitamins and minerals have long been used to treat nutrient deficiencies; however, in recent years supplements have been promoted as a means for overall health and longevity. According to the National Health and Nutrition Examination Survey, in 2012, it was estimated that 52 percent of the population were taking supplements.

Despite high use, there is no agreement on whether individual vitamins or minerals or combination supplements should be taken to prevent or treat heart disease. The U.S. Dietary Guidelines Advisory Committee recommend three diets to reduce heart disease risk: a healthy American diet low in saturated fat, trans fat and red meat, but high in fruit and vegetables; a Mediterranean diet; and a vegetarian diet.

In this review, researchers looked at 179 randomized controlled trials on vitamin and mineral supplement use published from January 2012 to October 2017 to determine if a benefit existed. This time frame includes papers published before and after the U.S. Preventive Services Task Force issued guidelines on the use of vitamins, minerals and multivitamins for primary prevention of cardiovascular disease and cancer in 2013.

Researchers found that data on the four most commonly used supplements -- multivitamins, vitamin D, calcium and vitamin C -- showed no consistent benefit for the prevention of cardiovascular disease, myocardial infarction or stroke, nor was there a benefit for all-cause mortality. Folic acid alone and B-complex vitamins in which folic acid was a component did show a reduction in stroke; however, niacin (vitamin B3) and antioxidants were associated with an increased risk of all-cause mortality.

These findings confirm the latest U.S. Preventive Services Task Force recommendation in 2014 that stated, "current evidence is insufficient to assess the balance of benefits and harms of single or paired nutrient supplements for the prevention of cardiovascular disease and cancer."

The one exception seems to be the benefit of folic acid for stroke prevention. A 2015 publication from the China Stroke Primary Prevention Trial (CSPPT) study showed that folic acid supplements may reduce cardiovascular disease and stroke risk. The current JACC review also showed a 20 percent reduction in stroke with folic acid alone.

A May 7 JACC study from the CSPPT also showed hypertensive adults with low platelet count who took a daily pill of both enalapril and folic acid daily saw a 73 percent risk reduction in first stroke when compared to enalapril alone.

"Folic acid administration and the reduction of cardiovascular disease through stroke seen in the Chinese CSPPT trial provides the only example of cardiovascular disease risk reduction by supplement use in the period following the Preventive Services Task Recommendation," said David J.A. Jenkins, MD, PhD, DSc, lead author of the review and professor and Canada research chair in nutrition and metabolism, Department of Nutritional Sciences, University of Toronto. "Whether these data are sufficient to change clinical practice in areas of the world where folic acid food fortification is already in place is still a matter for discussion."

Limitations of the review include: the researchers did not consider data from cohort studies, which are longer and more representative of the general population than randomized clinical trials. Also, grouping many types of antioxidants may have been suboptimal since their mechanisms of action may also be very different.