Another Study Finds Little Benefit and Some Harm From Most Nutritional Supplements

Gerald Chodak, MD


May 23, 2019

This transcript has been edited for clarity.

Hello. I'm Dr Gerald Chodak, for Medscape. In today's commentary I will revisit the question of whether dietary supplements are good for people's health.

Chen and colleagues[1] have recently reported data from the National Health and Nutrition Examination Survey, which included information from nearly 31,000 adults over age 20 years. Surveys were completed annually, and in each survey, individuals were questioned about dietary intake, nutrition intake, and supplement use during the previous 30 days. Using the National Death Index, the investigators analyzed whether people were dying from all causes, cancer, or cardiovascular disease.

This analysis resulted in three main findings. First and most important, the ever-use of supplements did not alter the outcomes in any way; however, there was a benefit from taking in vitamins A and K, zinc, magnesium, and copper. This benefit was not from using supplements; rather, it was from normal dietary intake of these vitamins and minerals. More alarming, people who had a higher-than-normal intake of calcium (more than 1000 mg daily) from supplements had an increased risk for death.

This is not the first study to report the lack of clear benefit from taking supplements, but it raises a number of questions that have yet to be resolved. First, are clinicians questioning their patients about the intake of supplements? Are they trying to find out about any possible interactions between the supplements being taken and conventional drugs that are being prescribed? We know that some of these do interact in a negative way. For example, some supplements reduce the effectiveness of chemotherapy, and other drug interactions do occur. So, without having that conversation, it's not possible for doctors to caution their patients about the potential harms.

Next, [we still don't know] why people continue to take these supplements in the absence of clear benefit. Most of them probably believe that a supplement is unlikely to cause harm even if it doesn't help them. But we know that that's not the case. So we need to improve awareness among our patients about these potential downsides.

A more global question is why we continue to have no regulation or very little regulation of the supplement industry, which is a multi-billion-dollar industry, at the present time. Why is it that conventional drugs must go through rigorous testing, but that same rigorous testing is not required for dietary supplements? There seems to be an incredible disconnect, as both have the potential to cause harm.

Perhaps one day we will find out whether these things are doing any real good. But until that time, I believe that greater caution and awareness are needed. I look forward to your comments. Thank you.

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