A new study from the Department of Psychiatry at Columbia University Medical Center published in The American Journal of Clinical Nutrition has found that a diet high in refined carbohydrates may lead to an increased risk for new-onset depression in postmenopausal women.

Researchers examined data from more than 70,000 postmenopausal women who participated in the National Institutes of Health’s Women’s Health Initiative Observational Study between 1994 and 1998 and analyzed their dietary glycemic index, glycemic load, the types of carbohydrates they consumed, and their corresponding depression data.

We’ve long known that consumption of carbohydrates increases blood sugar levels, depending on the type of carbohydrate ingested.  Doctors measure this blood sugar rise on a glycemic index, or GI scale, on a scale of 0-100 to measure the amount of sugar found in the blood after ingestion.   The more highly refined a food, the higher its score on the glycemic index.  Studies have also shown that highly refined foods including white bread, white rice, and sugared soda trigger the body’s hormonal response to reduce blood sugar levels. This study has now revealed what some of us have long suspected in ourselves – that this hormonal response to reduce sugar in the blood may cause or increase mood changes, fatigue, and other symptoms of depression.

In post-menopausal women specifically, this study has shown that higher dietary GI scores and a diet of added sugars and highly refined grains correspond to a higher risk of new-onset depression symptoms.  As well as the opposite – that a decreased risk of depression corresponded to an increased consumption of a more balanced diet of fiber, whole grains and vegetables.   Other researchers have found similar results – a study of 3,456 middle-aged civil servants, published in British Journal of Psychiatry found that those with a diet high in processed foods had a 58% increased risk for depression, compared to those whose diets contained more whole foods had a 26% reduced risk for depression.

We also know there is a circular aspect to eating refined carbohydrates – eating sugar causes more sugar cravings.  Studies show that a decrease in blood sugar stimulates hunger, which according to the American Heart Association, may explain why we crave highly refined foods – for the quick energy source and serotonin release.  Some experts believe people who crave carbohydrates may have a low serotonin level to begin with.

Researchers from Columbia University have said further study is needed to understand the implications of these results, and to confirm the results in a broader population.  But, these initial findings do suggest the possibility of a dietary treatment intervention or as a preventative measure.

To read more about the diet and depression connection, visit PsychCentral.com.