Snacking on simple carbs may fight insomnia

By Anne Harding

NEW YORK (Reuters Health) - Dining on quickly digested, high glycemic index (GI) foods a few hours before bedtime may help people drift off to sleep a bit more easily, Australian researchers report.

An evening snack of simple carbs could offer a "valuable" way to combat insomnia, if other researchers confirm these findings, Dr. Chin Moi Chow and colleagues from the University of Sydney in New South Wales conclude.

"Getting a good night's sleep is also about having good sleep habits and avoiding caffeine and alcohol before bedtime," Chow told Reuters Health in an e-mail. "If you struggle to fall asleep even after doing all this, you can discuss with your doctor if using a high GI evening meal might help you. It may also potentially help those who struggle to fall asleep after shift work or overseas travel."

GI is a number from 1 to 100 that ranks carbohydrates based on how quickly they cause blood sugar to rise. Low-GI foods, like oatmeal and vegetables, cause only a gradual increase in blood glucose and typically contain plenty of fiber, while high-GI foods such as white rice or bananas contain simpler carbohydrates and less fiber.

Carbohydrates are known to increase blood levels of tryptophan - needed to produce serotonin -- which promotes sleepiness, Chow and her team note in the American Journal of Clinical Nutrition. High-GI foods also boost the amount of tryptophan in the blood compared with levels of other amino acids, which may further speed up serotonin production, they add.

To investigate whether the GI of a carbohydrate meal influences sleep, the researchers had 12 healthy men undergo four different tests each: a meal of low-GI Mahatma rice eaten 1 or 4 hours before bedtime and a high-GI Jasmine rice dinner, again consumed at 1 or 4 hours before bed.

When the men ate the high-GI meal 4 hours before going to bed, they took 9 minutes to fall asleep, compared with 17.5 minutes after they ate the low-GI meal at the same time. The men took 14.6 minutes to drop off when they ate the high-GI meal 1 hour before bed.

"We are planning to conduct further testing in this area in people with insomnia because our study used good sleepers (with) little room for sleep improvement. It may be that in people with sleep difficulty, the high-GI meal can...help with consolidating sleep, in addition to helping them fall asleep more readily," Chow noted.

Chow said other foods that might have a similar effect include some types of bread, potatoes, cereal bars, and certain breakfast cereals. "Our group is planning to test other high-GI foods and fine tune the amount in terms of the GI and also the glycemic load," she added.

"Individuals with diabetes or obesity are often advised to adopt a low-GI diet, so use of a high-GI meal or snack to promote sleep may not be appropriate for them."

SOURCE: American Journal of Clinical Nutrition, February 2007.