Vitamins & Supplements Archive


Too much vitamin D may harm bones, not help

A study shows that, for many people, less is more when it comes to vitamin D.

There's no question that vitamin D can help build strong bones. But there may be a sweet spot when it comes to how much.

A study published in the Aug. 27 issue of JAMA found that, compared with people who took moderate amounts of vitamin D, adults who took large amounts daily not only didn't see additional gains in bone density, but in some cases ended up worse off.

Omega-3 fats don’t reduce the risk of diabetes or improve blood sugar control

Research we're watching

While eating more foods rich in omega-3 fatty acids may lower the risk of heart attack, that doesn't seem to reduce the risk of developing diabetes, according to a study published Aug. 24 in The BMJ. Prompted by past findings that this type of healthy fat might reduce diabetes risk and improve blood sugar (glucose) control, researchers decided to look further into the issue. They reviewed 83 randomized trials involving more than 120,000 people, both with and without diabetes. Each trial went on for six months or longer. These trials looked at whether increasing consumption of omega-3 fats (derived from fish or plants), omega-6 fats (such as those in soybean or corn oil), or total polyunsaturated fats could help lower blood glucose or reduce the risk of developing diabetes. They found that increasing the amount of omega-3, omega-6, or total polyunsaturated fats in the diet over an average study period of nearly three years didn't seem to have any effect on glucose metabolism or diabetes risk. It didn't matter whether the additional healthy fats came from supplements, enriched foods, or foods that were naturally rich in these fats.

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Taking supplements for your heart? Save your money

Research we're watching

Yet another study has found that most vitamin, mineral, and other nutritional supplements provide no protection against heart disease.

The new analysis, published July 8 in Annals of Internal Medicine, reviewed data from hundreds of clinical trials that pitted 16 different vitamins or other supplements against placebos. Most of them — including vitamin A, vitamin B6, vitamin D, multivitamins, calcium, iron, and selenium — showed no association with a higher or lower risk of heart disease or death.

Should I get my vitamin D levels checked?

On call

Q. Are there any particular reasons why men should get a routine blood test to check for a vitamin D deficiency?

A. The importance of sufficient vitamin D for bone health has a long history. In the past few decades, several studies have suggested that vitamin D might have other health benefits as well.

Beware of potential health risk related to supplements

Research we're watching

Do you know someone who is taking supplements in hopes of boosting their energy levels, gaining muscle, or losing weight? You may want to warn them about potential dangers. A study published online June 5, 2019, by the Journal of Adolescent Health found that products sold to boost energy, promote weight loss, or build muscle were linked to three times the number of severe medical events compared with vitamins. Researchers came to this conclusion after looking for supplement-related adverse events reported between January 2004 and April 2015 to the FDA. In total, they identified 977 cases of harm linked to supplements. Of those, 40% were severe medical events that resulted in death or hospitalization. While energy, weight loss, and muscle-building supplements appeared to be the riskiest, products sold to promote sexual function or to cleanse the colon were problematic as well. The FDA has found that some of these supplements contain dangerous substances or contaminants, such as pesticides, harmful chemicals, or heavy metals. Past studies have connected weight-loss and muscle-building supplements with serious, sometimes fatal, health problems, including liver damage, stroke, and testicular cancer.

Image: ronstik | Getty Images

Skip vitamins, focus on lifestyle to avoid dementia

News briefs

Vitamins and supplements won't help stave off dementia, but a healthy lifestyle might, suggest new guidelines released May 19, 2019, by the World Health Organization (WHO). The WHO warns that the number of new dementia cases around the world — currently 10 million per year — is set to triple by 2050. While there's no cure for any kind of dementia (such as Alzheimer's disease and vascular dementia), the WHO says it may be possible to delay the onset of the disease or slow its progression. The key: managing modifiable risks, such as chronic disease and unhealthy habits. The guidelines recommend that you keep your weight, cholesterol, blood pressure, and blood sugar under control; get lots of exercise; and eat a Mediterranean-style diet (which emphasizes olive oil, fruits, vegetables, nuts, and fish; minimizes red meats and processed meats; and includes a moderate amount of cheese and wine). The WHO also advises that you don't smoke and you avoid harmful use of alcohol (no more than one drink per day for women, no more than two drinks for men). But don't count on supplements to help you stave off dementia. The WHO says there's no evidence that vitamin B, vitamin E, multivitamins, or fish oil supplements help reduce the risk for dementia. The agency recommends against using supplements as a means to ward off cognitive decline.

Image: © kali9/Getty Images

The importance of potassium

Potassium is necessary for the normal functioning of all cells. It regulates the heartbeat, ensures proper function of the muscles and nerves, and is vital for synthesizing protein and metabolizing carbohydrates.

Thousands of years ago, when humans roamed the earth gathering and hunting, potassium was abundant in the diet, while sodium was scarce. The so-called Paleolithic diet delivered about 16 times more potassium than sodium. Today, most Americans get barely half of the recommended amount of potassium in their diets. The average American diet contains about twice as much sodium as potassium, because of the preponderance of salt hidden in processed or prepared foods, not to mention the dearth of potassium in those foods. This imbalance, which is at odds with how humans evolved, is thought to be a major contributor to high blood pressure, which affects one in three American adults.

Should you be taking an omega-3 supplement?

The answer to that question is becoming clearer, thanks to new research.

Some 10% of American adults regularly take an omega-3 supplement, despite uncertainty about whether these products truly live up to their health claims. But two new studies published in November 2018 shed some light on who might benefit from omega-3 supplements — and who probably won't.


The first study was the Vitamin D and Omega-3 Trial (VITAL), a large multiyear study with 25,871 healthy adults with no history of cardiovascular (heart or blood vessel–related) disease and at "usual risk" for it. The group was racially diverse and chosen to be representative of the general population, says the study's lead author Dr. JoAnn E. Manson, professor of medicine and the Michael and Lee Bell Professor of Women's Health at Harvard Medical School.

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