A study published this week indicates that a diet high in refined carbohydrates may increase the risk of developing depression.
More than 70,000 post-menopausal women participated in the National Institutes of Health's Women's Health Initiative Observational Study between 1994 and 1998. Researchers at the department of psychiatry at Columbia University Medical Center compared the incidence of depression amongst these women with the type of carbohydrates they were eating.
Carbohydrates are categorized according to the levels of sugar found in the blood soon after consumption. Those which cause a sudden increase in blood sugar levels are said to have a high glycaemic index (GI), whereas those that release sugars more gradually have a low GI. The more highly refined carbohydrates, such as white bread, white rice, have a higher GI.
It was shown that the risk of new-onset depression among this sample of post-menopausal women was higher in those women eating foods with a high GI. The more high GI foods they had in their diet, the more likely they were to develop depression. Conversely, eating more low GI foods, such as dietary fiber, whole grains, vegetables and non-juice fruits, lowered the risk of depression.
The high blood sugar levels that arise after eating refined carbohydrates trigger a hormonal response to remove the excess sugar. It is thought that the resulting low blood sugar levels may cause feelings of fatigue, and exacerbate symptoms of depression, such as mood changes, and apathy.
Although firm conclusions can not been drawn from a single study, these data suggest that dietary interventions may be beneficial in the prevention and treatment of depressive disorders. It will be interesting to determine whether similar results are obtained in studies of the general population.