Diet Linked To Daytime Sleepiness And Alertness
May 8, 2013

Fat Makes You Sleepy, Carbs Keep You Buzzed

Brett Smith for - Your Universe Online

Many people rely on caffeine to keep themselves alert and productive during the day. However, a new study in the journal SLEEP suggests a person´s diet can contribute to or reduce daytime sleepiness and alertness as well.

In the study, Penn State researchers found a“¯high-fat diet increased objective daytime sleepiness, or a person´s ability to take an intentional nap. They also found a high-carbohydrate diet was associated with raised levels of alertness. Both results were found regardless of test subjects´ gender, age, body mass index, total amount of sleep per night, and caloric intake.

“Increased fat consumption has an acute adverse effect on alertness of otherwise healthy, non-obese adults,” said lead author Dr. Alexandros Vgontzas, a professor of psychiatry at the Penn State College of Medicine.

The researchers recruited 31 “healthy, non-obese normal sleepers” between the ages of 18 and 65. The volunteers spent four consecutive nights in a sleep lab where they were monitored by the scientists. The research team calculated the volunteers´ total sleep time by averaging volunteers´ total sleep on the second and third nights.

On the fourth day, the research team tested for objective daytime sleepiness using the Multiple Sleep Latency Test (MSLT), a diagnostic tool used to measure the time elapsed from the start of a designated nap period to the first signs of sleep. The idea is the sleepier the subjects are, the faster they will fall asleep.

Meals were also provided five times to the volunteers after each MSLT so their diet could be assessed.

In their study, the authors noted previous studies had found a connection between diet and subjective sleepiness, or visible signs of sleepiness such as nodding off. However, the new study adds to a growing body of research showing a similar connection between diet and objective sleepiness.

“Our findings are consistent with previous studies that showed that high fat consumption in contrast to high carbohydrate intake affects adversely subjective sleepiness and performance,” the team wrote. “However, the exact mechanisms involved are not known and may include different factors such as cholecystokinin and proinflammatory cytokines.”

Vgontzas added the study´s findings could have larger social implications.

“Excessive daytime sleepiness and fatigue are very prevalent in the modern world and on the rise,” he said. “It appears that a diet high in fat decreases alertness acutely, and this may have an impact on an individual´s ability to function and also public safety.”

Study after study appears to back up Vgontzas´ claim of sleep disorders affecting public safety. A recently released report from the Virginia Tech Transportation Institute found 20 percent of all collisions are the result of driver fatigue. Other studies have shown the same dangers for the aviation and rail industries.

In their conclusion, the researchers suggested a high-fat diet could have negative lifestyle impacts beyond just sleep.

“Future studies are needed to confirm these findings and explore the effects of chronic high fat consumption on the quality of life,” they wrote.