Q. Can eating processed food cause depression?
A. If you need another reason to cut down on processed foods and eat more fruits, vegetables and fish, here it is.

A. If you need another reason to cut down on processed foods and eat more fruits, vegetables and fish, here it is. A study published in the November 2009 issue of the British Journal of Psychiatry suggests a link between eating lots of processed foods and increased vulnerability to depression.

The researchers studied the diets of English government workers between the ages of 35 and 55. Participants were grouped based on how often they ate whole foods versus processed foods. The "whole foods" group ate plenty of fruits, vegetables and fish. The "processed food" group's diet was heavily loaded with sweets, fried food, processed meat, refined grains and high-fat dairy products. Five years later, participants answered a questionnaire designed to measure symptoms of depression.
Those who ate the most whole foods had 26 percent less risk of future depression than those who ate the least whole foods. Those who ate the most processed foods had a 58 percent higher risk of depression than those who ate few processed foods. Even after accounting for smoking, physical activity, weight, chronic diseases, age and sex, the distinction remained.
The researchers suggest several explanations for their findings. Fruits and vegetables are loaded with antioxidants, and high antioxidant levels have been associated with lower risk of depression. Low dietary intake of the B vitamin folate, naturally found in many vegetables, has been linked to depression in middle-aged men. Lastly, some research suggests the omega-3 oils in fish may have a protective effect in preventing depression.
An alternative interpretation of the data could be that depression affects what people eat, rather than the other way around. The authors tested this issue and did not find this to be the case in their study group. Even so, it is possible some folks who are more prone to depression live a lifestyle where more processed food is consumed.
While there is still a need for more research, it makes sense to eat more whole foods and fewer processed foods. Eating healthy foods improves physical health. Physical health and mental health are closely related.
You can start gradually by eating an additional fresh fruit and vegetable each day. Eat fish at least twice a week. Try substituting one of your snacks with raw carrots, fruit, nuts or whole grain crackers instead of chips or cookies.

Amy Tousman is a registered dietitian and certified diabetes educator with Nutrition Unlimited in Kailua. Send your questions to: Prescriptions, Island Life, The Advertiser, 605 Kapiolani Blvd., Honolulu, HI 96813; islandlife@honoluluadvertiser.com; or fax 535-8170. This column is not intended to provide medical advice.