Vitamin D and calcium, when combined in one supplement, even increased stroke risk.
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  • A new study, published June 8 in Annals of Internal Medicine, further suggests that investing in supplement pills and powders won't reduce your risk of heart-related disease or lengthen your life.
  • Researchers looked at more than 100 prior studies including 16 kinds of supplements and found that only two types, folic acid and omega-3, helped reduce people's heart-related disease risks.
  • Supplements that combined vitamin D and calcium were found to increase a person's risk of stroke.
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There's plenty of evidence that suggests stocking up on vitamin supplements to stay healthy is a waste of money, if not harmful to health, and a robust new study adds even more weight to that argument.

The meta-analysis, published on June 8 in Annals of Internal Medicine, included 105 previous studies and looked at how 16 different types of supplements (like vitamin D and folic acid) and eight eating habits (including the Mediterranean diet and reduced salt intake) affected people's risk of developing cardiovascular disease, heart attack, stroke, and coronary heart disease, as well as their risk of dying from any cause over the given period. All the studies included were randomised controlled trials, the strongest study design out there.

Researchers found that 14 of the 16 supplements were, on the whole, ineffective at reducing heart-related disease risks or lowering the risk of dying from any cause. These supplements were: antioxidants, B-carotene, vitamin B complex, multivitamins, vitamin A, vitamin B6, selenium, niacin, vitamin C, vitamin E, vitamin D, vitamin D with calcium, calcium, and iron.

The only supplements that seemed to be beneficial for reducing heart-related disease risks were folic acid, which was associated with a reduced stroke risk, and omega-3, which was linked to a reduced risk of myocardial infarction, or heart attack. A low-sodium diet was also connected with a lower stroke risk, but no other diets seemed to affect disease risk.

"This study can help those who create professional cardiovascular and dietary guidelines modify their recommendations, provide the evidence base for clinicians to discuss dietary supplements with their patients, and guide new studies to fulfill the evidence gap," the study authors wrote.

Vitamin D and calcium, when combined in one supplement, increased stroke risk

Most of the supplements had no effect, either positive or negative, on disease risk. But vitamin D and calcium, when combined, actually increased stroke risk.

A previous study, published in April 2019, also found that these two supplements could have potentially harmful effects. Researchers found that people who took vitamin D supplements without have a diagnosed vitamin D deficiency had greater risks for cancer and death than people who didn't take any vitamin D supplements.

They also found that people who took calcium supplements were more likely to develop cancer, but that eating foods high in calcium had no effect on cancer risk. Researchers were unable to pinpoint exactly why this was the case, but theorise that the excess calcium from supplements increases hormone production.

The new study had some limitations, like that many of the former studies researchers analyzed focused on specific populations, such as all Chinese people. That means their findings can't be generalised to everyone, or even all Americans, since lifestyle factors and diets differ between the two countries.

Two doctors not associated with the study said that these new findings offer important insights, but more research needs to be done. "Unfortunately, the current study leaves us with the same foggy conditions that we started with," Dr. Amitabh C. Pandey and Dr. Eric J. Topol wrote in their editorial review. "Until these conditions clear, it would be reasonable to hold off on any supplement or diet modification in all guidelines and recommendations."

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