Another study has found that the most common vitamin and mineral supplements (multivitamins, vitamin D, calcium, and vitamin C), don't offer hoped for health benefits, and may actually carry some risks. This latest study was a review of other studies, and examined whether specific vitamins or minerals would lower the risk of cardiovascular disease (including heart attacks and strokes) and death from any cause (referred to as all cause mortality"). [Posts discussing other research finding problems with supplements.]
In general, the review of studies of popular supplements (multivitamins, vitamin D, calcium, and vitamin C) show no consistent benefit (no significant effect) for the prevention of cardiovascular disease, heart attacks, or stroke, nor any lowering of death (all cause mortality). On the other hand, folic acid and B-vitamins with folic acid, B6, and B12 reduced stroke (folic acid showed a 20% reduction in stroke), but niacin and antioxidants were associated with an increased risk of death from any cause (10% increase). But overall the effects in the studies were small. Vitamin D did not show any benefits in reducing death, but the researchers pointed out that many vitamin D studies are now under way, and the results of vitamin D studies so far are mixed (e.g. 16 showing positive effects from vitamin D, 17 showing a more favorable effect in the control group, and 10 neither).
On the other hand, the researchers stressed that eating a well balanced diet has lots of health benefits and is recommended by the U.S. Dietary Guidelines Advisory Committee. Three dietary patterns are frequently discussed as beneficial: 1) a healthy American diet (sometimes called a "prudent diet") low in saturated fat, trans fat, and red meat, but high in fruit and vegetables, 2) a Mediterranean diet, and 3) a vegetarian diet. All 3 of these diets are rich in fruits and vegetables (which means increased fiber), are relatively rich in vitamins and minerals, and meet Dietary Reference Intake guidelines.
From Science Daily: Most popular vitamin and mineral supplements provide no health benefit, study finds
The most commonly consumed vitamin and mineral supplements provide no consistent health benefit or harm, suggests a new study led by researchers at St. Michael's Hospital and the University of Toronto. Published today in the Journal of the American College of Cardiology, the systematic review of existing data and single randomized control trials published in English from January 2012 to October 2017 found that multivitamins, vitamin D, calcium and vitamin C -- the most common supplements -- showed no advantage or added risk in the prevention of cardiovascular disease, heart attack, stroke or premature death. Generally, vitamin and mineral supplements are taken to add to nutrients that are found in food.
The study found folic acid alone and B-vitamins with folic acid may reduce cardiovascular disease and stroke. Meanwhile, niacin and antioxidants showed a very small effect that might signify an increased risk of death from any cause.
His team reviewed supplement data that included A, B1, B2, B3 (niacin), B6, B9 (folic acid), C, D and E; and beta-carotene; calcium; iron; zinc; magnesium; and selenium. The term 'multivitamin' in this review was used to describe supplements that include most vitamins and minerals, rather than a select few.
"In the absence of significant positive data -- apart from folic acid's potential reduction in the risk of stroke and heart disease -- it's most beneficial to rely on a healthy diet to get your fill of vitamins and minerals," Dr. Jenkins said. "So far, no research on supplements has shown us anything better than healthy servings of less processed plant foods including vegetables, fruits and nuts."