A new study has evaluated the long-term health effects of 27 micronutrient supplements. The work draws on a massive collection of evidence to score each supplement on its cardiometabolic effects, including its influence on cardiovascular disease and type 2 diabetes.
The new systematic review and meta-analysis, which was published in the Journal of the American College of Cardiology, used data from nearly one million participants in 884 randomized controlled trials. The authors took a look at some of the most popular fatty acids, amino acids, vitamins, minerals, antioxidants and polyphenols available as supplements. Here are the results:
The Good
Three supplements showed the most impressive results for reducing major cardiometabolic events:
N-3 fatty acid (also known as Omega-3 fatty acid) reduced the risk of cardiovascular mortality, myocardial infarction, and coronary heart disease events by 7-15 percent.
Folic acid reduced the risk of stroke by 16 percent.
Coenzyme Q10 reduced the risk of all-cause mortality by 32 percent.
According to a press release, these micronutrients protect heart health because they are antioxidants. Oxidative stress contributes to cardiovascular illness, and antioxidants are believed to reduce that stress.
A range of other supplements were found to have some beneficial effect on blood pressure and cholesterol:
N-6 fatty acid, l-arginine, l-citrulline, vitamin D, magnesium, zinc, α-lipoic acid, melatonin, catechin, curcumin, flavanol, genistein, and quercetin.
The Bad
One supplement, in particular, showed strong negative effects: beta-carotene.
Beta-carotene supplements were linked with an increased risk of stroke, cardiovascular disease mortality, and all-cause mortality. In each case, the supplement appeared to increase the risk by about 10 percent.
The evidence for beta-carotene’s negative effect was only rated as “low quality,” though other another recent study found a similar result.
Other academics have argued that beta-carotene protects against diabetes risk factors, and the nutrient has been central to global public health initiatives. But most experts were already skeptical about the need for beta-carotene supplementation in those of us lucky enough to enjoy a healthy and diverse diet.
The Neutral
Several micronutrients were not associated with any cardiometabolic benefits. Vitamin C, Vitamin E, and selenium all showed no effect at all.
Supplements and Diabetes
Although the study identified more than a few micronutrients supplements that may have positive effects on markers of diabetes health, only one of those was rated as “high quality” evidence. The basic takeaway from this large study is that vitamin and mineral supplements don’t have much effect on diabetes, one way or that other.
The one apparent exception: Curcumin, the bright yellow chemical found in turmeric, was found to reduce fasting blood insulin levels.
There’s some evidence that curcumin can be helpful for people with diabetes, but medical authorities do not recognize any significant benefits to the supplement. Turmeric and curcumin are not, for example, listed among the supplements that the American Diabetes Association considers potentially important for people with diabetes.
Some members of our community love taking turmeric supplements, although not always to help with blood sugar. There are several other health benefits associated with this trendy supplement and ingredient. Check out our partner Everyday Health’s article: Turmeric (Curcumin): A Complete Scientific Guide.
Do We Need Supplements?
Micronutrients are essential to human life, but only minuscule amounts are necessary for good health, and many experts are suspicious about the booming micronutrient supplement market. A varied diet generally provides us with all the micronutrients that we need.
In the developing world, where access to healthy food can be limited, micronutrient deficiency is often a big public health problem. In the United States, most people get all the vitamins and minerals they need from their diets, but about one-third of the population is at risk of some deficiency. It’s especially common among communities of lower socioeconomic status.
For those of us that are not food insecure, authorities do not generally recommend the use of micronutrient supplements. The National Institutes of Health, for example, only recommend their use in certain specific cases: pregnant women need iodine supplements, and vegans may need vitamin B12 supplements.
An editorial published alongside the new study suggests that micronutrient supplementation may someday become a common element of preventive health, although much more study is needed to strengthen evidence and determine exactly which supplements should be used in which dosages.
You can find a chart summarizing the effects of all 27 micronutrients and scored by the strength of evidence right here.