A new review finds that the most widely used supplements do not protect the heart against cardiovascular disease. However, folic acid may prevent stroke.
The National Institutes of Health (NIH) estimate that one third of the entire population of the United States are taking some form of supplement.
Supplements are meant to raise our nutritional intake when food alone is not enough to provide the daily recommended dose.
However, some claim that supplements may prevent chronic disease such as cancer or cardiovascular disease.
Vitamins A, E, and C, for example, have been suggested to keep cancer at bay, while some studies have proposed that folic acid, vitamin E, and vitamin D might be helpful for preventing cardiovascular disease. However, the scientific evidence available is conflicting.
The official message that government authorities and nonprofit organizations have been putting forth to the public is that, even though supplements may help, food should always come first.
The main reasons for this are that food contains fiber and several bioactive compounds that cannot be found in a supplement, and that the evidence for the heart-protective benefits of supplements is insufficient.
So, researchers led by Dr. David J. A. Jenkins — a professor and Canada research chair in nutrition and metabolism at the University of Toronto — set out to examine existing studies in an attempt to determine whether vitamin and mineral supplements do, in fact, protect the heart.
Their findings were published in the Journal of the American College of Cardiology.
In 2014, the U.S. Preventive Services Task Force issued a statement that reported, “Currently, there is not enough evidence to determine whether taking a multivitamin will help prevent [cardiovascular disease] or cancer.”
For the new research, Dr. Jenkins and his team “conducted a systematic review and meta-analysis” of 179 randomized controlled trials published between January 2012 and October 2017 — both before and after the U.S. Preventive Services Task Force published their guidelines.
The researchers used studies from the Cochrane Library, MEDLINE, and PubMed databases.
The review revealed that the four most popular supplements — vitamin D, calcium, vitamin C, and multivitamins — have no cardioprotective benefit.
A significant exception, however, is the role of folic acid in preventing stroke. One randomized controlled trial called the China Stroke Primary Prevention Trial (CSPPT) showed a significant reduction in stroke risk for those taking folic acid.
Overall, it revealed that the intake of folic acid alone can reduce stroke risk by 22 percent. Additionally, people with high blood pressure who took folic acid in addition to their usual hypertensive medication had a 73 percent lower risk of stroke.
“Folic acid administration and the reduction of cardiovascular disease through stroke seen in the […] CSPPT trial provides the only example of cardiovascular disease risk reduction by supplement use in the period following the Preventive Services Task Recommendation.”
Dr. David J. A. Jenkins
“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,” he adds.