Does Melatonin Supplementation Damage the Heart?

If you’ve been taking melatonin, you may have been alarmed by the findings of a recent study reported in the popular media that found an association between long-term melatonin supplementation and an increased risk of heart failure.

Before you throw out your melatonin supplements and rush off to see a cardiologist, let’s consider this research and how its findings compare to other recent studies.

First of all, the study in question has not yet been published and it has not yet been subjected to peer review. Peer review is when other scientists look over all the data and statistical analysis to see if everything was done properly and to assess whether the study was conducted in accordance with accepted standards to be published in a high-quality research journal. Just because the study has not been peer reviewed and published doesn’t mean it’s not valid, but it means that it still hasn’t really been independently confirmed as legitimate.

One big issue that some informal reviewers have brought up is that melatonin use wasn’t measured or monitored directly. What the researchers did was look at a large number of electronic health records for self-reported and prescribed melatonin use.

While melatonin supplements are available without a prescription in the United States, it requires a prescription in several countries from which the data was drawn. This likely resulted in a significant under-reporting of melatonin supplementation from the U.S. data, as it is an extremely popular supplement in this country and its use probably wouldn’t be reported in the majority of electronic health records unless it was specifically asked about by the individual’s physician.

In addition, since the data came from electronic health data collected from physician records, it’s likely that the data was skewed towards those with sleep disturbances bad enough to seek professional care, rather than to simply self-treat.

So, this study may have a major classification error with a large number of melatonin users being classified as being part of the non-user control group.

In addition, we have to consider the most common reason why people take melatonin: insomina.

Chronic insomnia is a known significant risk factor in the development of heart failure and other forms of cardiovascular disease.

So, when we put together the high potential for classification error and the fact that the majority of melatonin users have insomnia, a risk factor for heart failure in and of itself, the findings of this study become a bit questionable, particularly when you add in the current lack of peer review.

If it were in agreement with other research in this area, we might be able to excuse some of the limitations of this study, but other studies on melatonin have not only not found an associated risk with heart disease. In fact, some have found benefits – including in patients diagnosed with chronic heart failure.

So, as with a lot of media-hyped research findings, I think the alarm over melatonin supplementation is premature at best. Any supplement, drug, or even food can cause harm to some individuals. But if you’ve been using melatonin in a reasonable dose (1 to 3 mg/day taken before bedtime is the most common recommendation, although significantly higher doses are still generally considered safe) and it has been helping you get more quality sleep, most likely the benefit to you outweighs any potential harm.

Until next time…

George F. Best, D.C.