By Craig William Raphael, MS5 & Darcy Green Conaway, MD
Numerous over-the-counter nutritional and vitamin supplements claim to possess a wide range of health benefits, including preventing and treating heart disease. However, data supporting these claims is often not provided. Here we discuss what medical research to date reveals regarding the use of fish oil, folic acid, coenzyme Q, and vitamins C, D, and E in preventing and treating coronary artery disease (CAD).
Fish oils are “essential” fatty acids obtained through supplements or by eating a diet rich in fish, flaxseed, walnuts, and other tree nuts. In 1969, it was observed that people who consumed large amounts of fish had low death rates from CAD, suggesting that fish oils may reduce the risk of CAD.1 However, data supporting this claim has been controversial. Clinical trials, such as the DART study in 1989 and the GISSI-Prevenzione trial in 1999, have reported that diets supplemented with fish oils led to reduced cardiac death, but subsequent trials failed to confirm this.3,4 The benefit of fish oil supplementation in CAD still remains unclear. Nevertheless, the American Heart Association recommends one serving of fatty fish or 1g of fish oils twice a week for good cardiovascular health.
Folic acid, or folate, is another nutritional supplement proposed to decrease CAD. Folate is a vitamin contained in green leafy vegetables, fruits, legumes, and some cereals. It was originally postulated that folate decreases blood levels of homocysteine, an amino acid derivative commonly elevated in patients with CAD and heart attacks. A 10-year trial showed that folate supplementation subtly reduced the long term mortality from CAD.10 However, the NORVIT trial, HOPE 2 study, and VISP study all showed that folate decreased homocysteine levels but failed to decrease the risk of serious cardiovascular events.9,12,13 Consequently, the benefit of folate supplementation still remains unclear.
Coenzyme Q (CoQ), a fat soluble vitamin-like substance found naturally in the body, is another dietary supplement sometimes used to treat heart failure and heart attacks. Due to its anti-inflammatory properties, CoQ is thought to decrease plaque formation and, in 2004, Yalcin et al. demonstrated low blood levels of CoQ in patients with CAD.17 However, few trials have proven a correlation between CoQ supplementation and decreasing CAD risk. Moreover, some common lipid-lowering medicines actually decrease CoQ levels without increasing CAD risk.15,18 Due to confusing data surrounding its use, CoQ is not recommended to prevent or treat CAD.
Finally, vitamins C, D, and E have all been suggested as supplements that may decrease CAD risk. Vitamin C, found in fruits and vegetables, theoretically prevents tissue damage that leads to plaque buildup within coronary arteries, but when administered as supplements, vitamin C failed to reduce the risk of CAD.21,22 Although low levels of vitamin D have been seen in patients with poor cardiovascular health, supplementation with this vitamin has not slowed the development of CAD in clinical trials.29 Lastly, the antioxidant property of vitamin E has been proposed as a possible mechanism to prevent CAD, but research studies have failed to support this proposal.30 Overall, there is a lack of convincing research that suggests that supplementation with any of these vitamins can combat CAD.
Regarding the vitamin and dietary supplements discussed above, none have undergone adequate clinical trials to unequivocally prove that they reduce the risk of CAD. Thus, fish oil, folic acid, CoQ, and the vitamins C, D and E all warrant further investigation before the American Heart Association can recommend them as prevention or treatment of CAD.
Craig William Raphael is a fifth-year medical student at the University of Missouri Kansas City School of Medicine and Darcy Green Conaway, MD, MSMA member since 2011, is an Assistant Clinical Professor and Staff Cardiologist at the University of Missouri-Kansas City School of Medicine and at Truman Medical Center in Kansas City.
Editor's note: This article is part of a special series brought to you by Missouri Medicine, the Medical Journal of the Missouri State Medical Association (MSMA). MedHelp, Missouri Medicine, and MSMA are collaborating to educate and empower health consumers by making the latest scientific studies and medical research available to the public. Learn more about MSMA and see more from Missouri Medicine.
This is a summary of the article"Nutritional and Vitamin Supplements: Do They Prevent Coronary Artery Disease?" by Craig William Raphael, MS 5 and Darcy Green Conaway, MD, which was originally published in the May/June 2012 issue of Missouri Medicine. The full article is available here.