A diet high in processed grains such as white bread, white flour and sugar could increase the risk of depression in older women, according to a study conducted by researchers from Columbia University that was published in the American Journal of Clinical Nutrition. In contrast, a diet high in whole grains and vegetables decreases the risk.
Approximately three percent of people in the United Kingdom suffer from depression. In the United States, the proportion of people over the age of 12 suffering from depression is eight percent.
The National Institute of Mental Health characterizes the main symptoms of depression as persistent feelings of anxiety, emptiness, guilt, helplessness, sadness, worthlessness, irritability, fatigue or restlessness; difficulty concentrating; changes in sleep patterns; and suicidal thoughts.
Diet can prevent, treat depression
Refined carbohydrates such as white flour and white rice are made by stripping away the high-fiber part of the seed. Consequently, these “white carbs” have much higher proportions of simple sugars and are lower in other nutrients. Typically, these foods score higher on the glycemic index (GI) scale, a measure of how much sugar is found in the blood after eating a certain food.
In order to compare the influence of different types of food on depression, the researchers collected data on more than 70,000 postmenopausal women who had taken part in the Women’s Health Initiative study between 1994 and 1998. They looked at the types of carbohydrates consumed, the glycemic load from these foods, and the rates of depression.
The researchers found that a higher consumption of sugar and refined grains was linked to a higher dietary GI score, and both of these were associated with an increased risk of new-onset depression. In contrast, women who ate more fiber, whole grains, vegetables and fruit (excluding fruit juice) had a lower risk.
“This suggests that dietary interventions could serve as treatments and preventive measures for depression,” researcher James Gangwisch said.
Cause and effect?
As a potential explanation for this connection, the researchers noted that the consumption of high GI foods leads to spikes in blood sugar, which then leads to higher insulin levels. High insulin, in turn, has been shown to worsen symptoms of depression including mood changes and fatigue. Additionally, the researchers remarked that a diet high in refined sugars and grains is associated with a higher risk of inflammation and cardiovascular disease, both of which are depression risk factors.
Other researchers were more skeptical, pointing out that the study was not designed to prove that the high GI diet actually caused the higher rates of depression.
“When you feed your body and brain healthy, whole, nutrient-rich foods, you feel better,” said dietitian and nutrition researcher Lona Sandon of the University of Texas. “You may feel better and have a better mood, simply because you know you are doing something good for your body.”
“What is not clear from the report is whether or not the depression or consumption of refined carbohydrates came first,” Sandon said. “Many people make poor food choices when they are depressed or even stressed, and may reach for refined carbohydrates — like chocolate — in an attempt to improve their mood.”
Another dietitian and nutrition researcher, Penny Kris-Etherton of Penn State University, had a more positive reaction, calling the study “part of an important piece of emerging literature.”
“People are just starting to explore the connection between nutrition and mental health,” Kris-Etherton said. “And I think this work will add fuel to a fascinating area of study, which is certainly worthy of more investigation.”
The researchers themselves acknowledged the limitations of the study and called for more research to confirm their findings in men and younger women.