Many people struggle with overwhelming tiredness during the day, a condition known as excessive daytime sleepiness (EDS).
About one in three Americans reports experiencing it, and it is more than just an inconvenience—it has been linked to higher risks of heart disease, obesity, and diabetes.
Now, new research shows that molecules in the blood may help explain why some people are more prone to EDS than others, with both diet and hormones playing a role.
The study, led by researchers from Mass General Brigham and Beth Israel Deaconess Medical Center, identified seven specific molecules in the blood, known as metabolites, that are strongly linked to daytime sleepiness.
The findings, published in eBioMedicine, suggest that the risk of EDS is influenced by a combination of internal biological processes, like hormone activity, and external lifestyle factors, such as diet.
“Our study suggests diet and genetics may play an important role in EDS,” said lead author Tariq Faquih, Ph.D., a postdoctoral fellow at Brigham and Women’s Hospital.
“As we learn what’s happening biologically, we are beginning to understand how and why EDS occurs, the early signs that someone might have it, and what we can do to help patients.”
The researchers analyzed blood samples from more than 6,000 participants in the Hispanic Community Health Study/Study of Latinos.
They looked at 877 different metabolites—small molecules shaped by diet and hormone levels—and compared them to self-reported levels of daytime drowsiness. To strengthen their results, the team replicated their findings in additional studies, including the Multi-Ethnic Study of Atherosclerosis as well as large cohorts in the UK and Finland.
Several important patterns emerged. Omega-3 and omega-6 fatty acids, often found in Mediterranean-style diets rich in fish, nuts, and seeds, were linked to a lower risk of EDS. In contrast, tyramine—a compound present in fermented and overripe foods—was tied to higher risk of sleepiness, especially in men.
The researchers also found that metabolites related to sex hormones, such as progesterone, may affect sleep through their interaction with melatonin, the hormone that regulates sleep-wake cycles.
The study highlights potential new approaches to managing daytime sleepiness. Dietary adjustments, supplements, or medications that target these metabolites could one day help reduce EDS. The authors caution that the research has limits: metabolite levels can be tricky to interpret, and questionnaires may not be as precise as clinical sleep tests.
Still, the work points to promising directions. “Conducting a clinical trial would be a big next step,” said Faquih. “It could help us understand whether omega-3s and omega-6s from diet can truly lower the risk of daytime sleepiness.”
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