About one in three Americans experiences excessive daytime sleepiness — that feeling of overwhelming drowsiness even after a full night’s sleep. And while nodding off at your desk might feel like a personal problem, researchers are beginning to uncover that there’s more to it than just being tired.

A new study from Mass General Brigham identified seven molecules in the blood that are linked to the condition. Known as metabolites, these naturally occurring compounds reflect a person’s diet, hormone levels and other internal processes.

Essentially, what you eat and how well your body hums along may be playing a key role in why you’re struggling to stay awake. Researchers analyzed blood samples from over 6,000 participants in a large health study of Hispanic and Latino populations. They also looked at questionnaire responses measuring how often participants nodded off during the day — think watching TV, reading or listening to a training module at work. These findings held up when tested in additional studies across the U.S., UK and Finland.

Among the standout results, researchers noted that omega-3 and omega-6 fatty acids, common in Mediterranean-style diets, were linked to a lower risk of excessive daytime sleepiness. On the flip side, tyramine [tye-ruh-meen] (found in fermented or overripe foods) was associated with greater sleepiness in men. Meanwhile, hormonal metabolites like progesterone also appeared to be linked to sleep regulation.

Eventually, researchers believe this could lead to dietary or pharmaceutical treatments, and they are eyeing a clinical trial to keep studying a solution. For now, you might not be the only one reaching for a second cup of coffee to get through the day.