The study published in the American Journal of Clinical Nutrition by J. Gangwisch et al, found women who had a higher glycemic index (GI) created by heightened consumption of refined grains and added sugars, had a higher risk of newly onset depression. By contrast, women with a diet more rich in fiber, vegetables, fruits and whole grains decreased their risk of depression.
“We found a progressively higher dietary GI to be associated with increasing odds of depression incidence in carefully controlled analyses,” the researchers said.
“We found added sugars, but not total sugars or total carbohydrates, to be strongly associated with depression incidence… We found that progressively higher consumption of whole grains was associated with lower odds for depression incidence, whereas the opposite was true for nonwhole/refined grains, with progressively higher consumption associated with higher odds for depression,” they wrote.
The research suggested refined foods reduced blood sugar levels, causing a “sugar high” and “crash” thereby bringing altering moods and fatigue - two major symptoms of depression.
There was, however, no association found between glycemic load and depression incidence.
James Gangswisch, an assistant professor of psychiatry at Columbia University Medical Center and the lead author of the study, told BakeryandSnacks.com these findings created opportunities for bakery and snack makers.
Creating a new market for low-GI products, for example, could very well work in the industry’s favor, he said.
What did the study look at?
The observational study involved cross-sectional analysis of 93,676 postmenopausal women aged 50-79 across 24 states in the district of Colombia. The study was conducted between September 1, 1994 – December 31, 1998, with 69,954 women participating in a follow-up three years later.
Food patterns were measured using a food-frequency questionnaire and depressive disorders and tendancies measured with the Burnam 8-item scale.
Gangswisch said they already knew people tended to reach for sweets and carbs when they felt depressed, but the aim of the research was to investigate whether consumption of bread and treats could influence one’s mental state.
“We did what we could call a cross-sectional with depression and consumption of carbs,” he said. “We would expect people who are depressed to be eating more carbohydrates than other people. We were interested in more new cases of depression. We excluded all the people depressed at the baseline and looked at the reports of their diet at baseline. We looked at the new cases of depression three years later.”
Findings showed participants with dietary GIs in the fourth and fifth quintiles were “significantly more likely to have depression three years later than were participants who were in the first quintile in energy-adjusted results”.
Similarly, there was a “significant trend” between added sugar consumption and depression three years later.
Industry opportunity
The study said future research into low-GI foods and depression should be conducted.
“Randomized trials should be undertaken to examine the question of whether diets rich in low-GI foods, such as legumes, cereals high in viscous sticky fibers, and temperate-climate fruit, could serve as treatments and primary preventive measures for depression in postmenopausal women,” they wrote.
Gangswisch said dietary intervention could help serve as treatment and a preventative measure for depression.
“A lot of it is eating in moderation,” he said. “It’s not going to kill you to have these foods once in a while. Evidently, these women [in the study] were just eating a lot more of this high glycemic index stuff, as opposed to every now and again you have white bread instead of whole grain bread, or a dessert here and there.”
Study limitations?
The researchers acknowledged some limitations in their cohort study.
In particular, they said the measurement of dietary exposures through questionnaires instead of through dietary biomarkers or food records could be considered a limitation. The assessment of depression – self-reported rather than through psychiatric interviews – could also be limiting.
In addition, the researchers noted that because the focus group was postmenopausal women they were unable to generalize about the broader population.
Source: The American Journal of Clinical Nutrition
Published June 24, 2015, doi: 10.3945/ajcn.114.103846
"High glycemic index diet as a risk factor for depression: analyses from the Women’s Health Initiative"
Authors J. Gangwisch, L. Hale, L. Garcia, D., M. Opler, M. Payne, R. Rossom, and D. Lane