Diabetes is one of the most serious health problems in the United States and around the world. According to Centers for Disease Control estimates, 1 in 10 American adults currently has diabetes. And, if the CDC projections are correct, those numbers will double or even triple over the next 40 years.
There are well-established links between disrupted sleep and risk of type 2 diabetes. But the exact relationship between the two is not fully understood. In the ongoing effort to better understand the causes and risk factors for diabetes, research in recent years has increasingly focused on the role of melatonin. Now, new research indicates that low levels of melatonin are associated with elevated risk for type 2 diabetes. The study, led by researchers at Boston’s Brigham & Women’s Hospital, found that women with the lowest levels of melatonin secretion had more than two times the risk of developing type 2 diabetes as those with higher melatonin levels.
Researchers used data from the Nurses’ Health Study, a long-term, large-scale project investigating a broad array of women’s health issues. Since its inception in 1976, the Nurses’ Health Study has collected information from more than 200,000 female nurses. For this study, researchers used information from women who provided blood and urine samples in 2000. First, researchers selected the women without diabetes, and monitored their health for the next 12 years. During the period of 2000-2012, 370 of the women developed diabetes. Using this sub-group, researchers analyzed melatonin levels. In their analysis, they controlled for other risk factors for type 2 diabetes, including body mass index, family history, high blood pressure, and lifestyle habits. They found:
- Lower melatonin levels associated with higher risk of diabetes
- Those with the very lowest levels of melatonin secretion had 2.17 times the risk for diabetes than those with the highest levels of melatonin
- Women with the highest levels of melatonin developed diabetes at a rate of 4.27 cases per 1,000. For women with the lowest levels of melatonin, the incidence of diabetes was 9.27 cases per 1,000.
This is the latest in a series of research breakthroughs that suggest melatonin plays an important role in metabolic functions and risk of diabetes. I wrote recently about studies that have found that mutations to the body’s melatonin receptor gene are associated with significantly heightened risk for type 2 diabetes. Other research has also found evidence of a relationship between melatonin levels on the onset of diabetes:
- Several studies involving mice and other animals have found melatonin secretion has an effect on insulin sensitivity and other markers of diabetes. This study showed improvements to insulin sensitivity and glucose tolerance in mice given supplemental melatonin. And in this study, blood pressure and blood glucose levels dropped in hamsters given melatonin. On the other hand, mice deprived of melatonin experienced diminished ability to metabolized glucose, likely as a result of increased resistance to insulin.
- Studies involving people have also shown links between insulin resistance and melatonin. This study of patients with metabolic syndrome found a strong association between melatonin levels and insulin levels in the human body. Many people with metabolic syndrome very often go on to develop diabetes.
How does melatonin work in the body to influence the onset of diabetes? We don’t yet have a definitive answer to that question. The current study, and other studies of melatonin and diabetes, have not identified the mechanism by which melatonin influences the development of diabetes. In discussing their results, researchers indicate that they believe evidence points strongly to melatonin’s role in the secretion of insulin.
Melatonin, best known as “the sleep hormone,” is critical to regulating the body’s 24-hour biological clock and sleep-wake cycle. Melatonin release is triggered by the absence of light. As night approaches, melatonin levels rise, preparing the body for sleep. Melatonin levels fall back as daytime arrives, and the body becomes alert and prepared for a waking day. Over years of scientific inquiry, our understanding of melatonin’s role in the body has broadened. We’re still learning about the range of melatonin’s influence. But the hormone is now recognized as having influence in several important biological functions, including the immune system and metabolic system.
So, does this mean people at risk for type 2 diabetes should start taking melatonin supplements? Definitely not.
We don’t know enough yet about melatonin as a factor in diabetes. Studies such as this latest one strongly point to a relationship, but it’s one that is not yet well understood. These and other research findings do not indicate that an increase of melatonin through supplements would work effectively to reduce the risk of type 2 diabetes. And supplemental melatonin comes with its own set of possible complications. Our bodies are expert at creating and regulating melatonin naturally. Introducing supplementation of the hormone into the body at an inappropriate dose, or at the wrong time of day, can interfere with the proper functioning of the body’s circadian clock. Melatonin should only be used when specifically recommended by a doctor after careful determination that it is an appropriate treatment.
That said, these results are yet another step forward in our understanding of the importance of melatonin, and in particular, its relationship to diabetes risk. Building on discoveries such as this may lead to new and more effective treatment and prevention strategies to combat this dangerous and all-too-common disease.
Michael J. Breus, PhD
The Sleep Doctor™