Posted on Jul 17, 2019, 1 p.m.
An analysis of over 200 clinical trials using 24 interventions conducted by John Hopkins Medicine suggests that almost all nutritional supplements or diets can’t be linked to longer life or protection from heart disease.
As published in the Annals of Internal Medicine the analysis also found that most of the supplements or diets weren’t associated with any harm, and only showed possible health benefits for some people from a low salt diet, omega-3 fatty acid supplements, and possibly folic acid supplements; supplements combining calcium and vitamin D were found to be linked to a slightly increased risk of stroke, according to the researchers.
52% of Americans take at least one daily vitamin or other dietary nutritional supplement according to the CDC; and as a nation $31 billion is spent on these over the counter products. This study adds to the increasing body of evidence that have found no health benefits from taking most of these products.
"The panacea or magic bullet that people keep searching for in dietary supplements isn't there," says senior author of the study Erin D. Michos, M.D., M.H.S. "People should focus on getting their nutrients from a heart-healthy diet, because the data increasingly show that the majority of healthy adults don't need to take supplements."
Data was collected from 277 randomized clinical trials evaluating 16 vitamins or other supplements and 8 diets for their association with mortality or heart conditions; data collected included 992,129 participants from around the globe.
Supplements and vitamins reviewed included: antioxidants, carotene, multivitamins, selenium, vitamin B complex, vitamins A, B3, B6, C, E, D, calcium, vitamin D and calcium, folic acid, iron and omega-3 fatty acid. Diet reviewed included: Mediterranean diet, reduced saturated fat diet modified dietary fat intake diet, replacing calories with more unsaturated fats diet, reduced fat diet, reduced salt diet in healthy people and those with high blood pressure, increased alpha linolenic acid diet, and increased omega-3 fatty acid diet. Each intervention was ranked by strength of evidence from high to very low risk impact.
The majority of supplements showed no link to increased/decreased risk of death or heart health; 3 studies including 3,518 healthy people following a low salt diet had 79 deaths; a 10% decrease in the risk of death was found in these people which was classified as a moderate associated impact.
5 studies involving 3,680 subjects with high blood pressure following a low salt diet had 674 heart disease deaths, these people were found to have a 33% decreased risk of death which was classified as moderate evidence of impact intervention.
41 studies involving 134,034 subjects investigating the impacts of omega-3 fatty acid supplements had 10,707 events such as heart attack or stroke, these studies were linked to an 8% reduction in heart attack risk and a 7% reduction in coronary heart disease and were ranked as being a low evidence of benefit to intervention link.
25 studies involving 25,289 healthy subjects showed a 20% reduced risk of stroke linked to folic acid; there were 877 strokes during these trials and the intervention was graded as being a low link to evidence of benefit.
20 studies investigated combination of vitamin D with calcium involving 42,072 subjects who had 3,690 strokes, suggesting a 17% increased risk of stroke and the evidence was ranked as moderate risk; there was no evidence the vitamin D or calcium taken alone had any health benefits or risks.
Studies suggesting the greatest impact of folic acid supplements reducing risk of stroke were noted to have been conducted in China were cereals and grains are not fortified with folic acid as they are in America, meaning the protective effect may not be applicable to regions where most people get enough folic acid in their diet. According to the authors there were no conflicts of interest and they did not receive financial support for this research study.
"Our analysis carries a simple message that although there may be some evidence that a few interventions have an impact on death and cardiovascular health, the vast majority of multivitamins, minerals and different types of diets had no measurable effect on survival or cardiovascular disease risk reduction," says lead author Safi U. Khan, M.D., an assistant professor of Medicine at West Virginia University.
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This article is not intended to provide medical diagnosis, advice, treatment, or endorsement.
Safi U. Khan, Muhammad U. Khan, Haris Riaz, Shahul Valavoor, Di Zhao, Lauren Vaughan, Victor Okunrintemi, Irbaz Bin Riaz, Muhammad Shahzeb Khan, Edo Kaluski, M. Hassan Murad, Michael J. Blaha, Eliseo Guallar, Erin D. Michos. Effects of Nutritional Supplements and Dietary Interventions on Cardiovascular Outcomes. Annals of Internal Medicine, 2019; DOI: 10.7326/M19-0341