Eating a lot of red meats, refined grains, french fries, and other typically Western foods will increase your risk of developing diabetes as an adult by more than half, according to a new study by Harvard School of Public Health researchers.
The study, published in this week’s Annals of Internal Medicine, is the first to link overall dietary patterns rather than specific foods to the development of type 2 diabetes, which affects 16 million Americans and can cause blindness, kidney failure, and heart disease.
Frank Hu, assistant professor of nutrition and cardiovascular disease and one of the study’s authors, said looking at the whole diet is an important shift in approach because it mirrors how people eat. Previous studies using the single-nutrient approach – looking individually at things like fat, sugar, and fiber – have provided important results, but could miss the big picture.
“We put so much emphasis on fat (in the past) that people think they can eat a diet loaded with refined carbohydrates like white bread, bagels, and doughnuts by lowering the fat,” Hu said. “We find that fat is not the primary factor for heart disease or diabetes.”
The study’s other authors are Fredrick Stare Professor of Epidemiology and Nutrition Walter Willett; Professor of Epidemiology and Nutrition Meir Stampfer; Associate Professor of Epidemiology and Nutrition Eric Rimm; and Rob van Dam of the Department of Chronic Diseases Epidemiology of the National Institute for Public Health and the Environment in The Netherlands.
Hu said finding the causes behind diabetes is particularly important because the incidence of the disease has rapidly increased worldwide over the past two decades, possibly because of the spread of Western diet and lifestyle. The World Health Organization expects the number of diabetics in the world, today between 120 million and 140 million, to double by 2025.
There are two types of diabetes. Type 1 diabetes mainly occurs in childhood and adolescence and is characterized by the body’s complete inability to produce insulin – the hormone that helps the body process sugar for energy. Without insulin, glucose builds up in the blood stream until it damages organs such as the kidneys, eyes, and heart. Untreated, it can eventually lead to blindness, renal failure, heart disease, and death.
Type 2 diabetes, which makes up between 90 percent and 95 percent of cases, usually occurs in adults over age 40 and is caused by a reduction in the body’s ability to use insulin. Type 2 diabetes in some cases can be controlled by diet and exercise. Though slower to cause damage than type 1, uncontrolled type 2 diabetes can cause the same complications.
One reason diabetes is dangerous, Hu said, is that people often don’t know they have it until high blood sugar levels start to cause complications.
“Diabetes is a silent killer, especially in the beginning (before it is diagnosed),” Hu said. “Clearly this has become a worldwide problem.”
The 12-year study tracked the dietary patterns of 42,000 men between the ages of 40 and 75, of which 1,321 developed type 2 diabetes.
Subjects filled out detailed dietary questionnaires every four years and provided information about their health status. From their responses, researchers identified two typical dietary patterns. The Western diet consisted of red meat, processed red meat, refined grains, high-fat dairy products, french fries, and desserts. The prudent diet consisted of higher levels of fruits, vegetables, whole grains, fish, and poultry.
In analyzing the data, subjects were further divided into five groups for each dietary pattern according to how well they fit the ideal prudent and Western diet. In the group that most closely fit the Western diet, 361 developed diabetes, a 59 percent greater risk than men whose diets were least compatible with Western diet. In the group that most closely fit the prudent pattern, 252 developed the disease, about 16 percent lower than those who did not follow a prudent diet.
The study also indicated that those who followed the Western diet were more likely younger, overweight, and less physically active than those who followed the prudent diet. The study’s results didn’t change, however, when adjusted for the effects of weight, age, and level of physical activity. The risk is particularly high when Western diet is combined with obesity and physical inactivity.
Hu said the message from this study is important for public health because it promotes an overall healthy eating pattern and lifestyle to prevent type 2 diabetes.