In recent years, a diet high in fat and low in whole grains, fruits, and vegetables has been dubbed a "western" diet. As the prevalence of type 2 (adult-onset) diabetes increases, studies suggest that the western diet may be at least partly to blame. However, previous studies have not analyzed dietary factors independent of other risk factors, such as obesity and physical activity. A recent study published in the
Annals of Internal Medicine
, which did analyze diet independently of obesity and physical activity, suggests that while a "western" diet may indeed increase the risk of type 2 diabetes, a "prudent" diet may reduce the risk.
For the purposes of this study, researchers defined a western diet as a diet high in red meat, processed meat, refined grains, French fries, high-fat dairy products, sweets and desserts, high sugar drinks, and eggs. A prudent diet was a diet high in vegetables, legumes, fruit, whole grains, fish, and poultry.
Thestudy began in 1986 when 51,529 male health professionals in the United States enrolled in the Health Professionals Follow-up Study conducted by Harvard School of Public Health. The men were between the ages of 40 and 75 and most of them were white. They completed a mailed questionnaire about medical history, diet, and other risk factors for major diseases in 1986 and every two years thereafter. This recent study of the effects of diet on diabetes included only 42,504 of the men, because researchers excluded men who had diabetes, cardiovascular disease, or cancer, since these diseases might have affected their dietary habits. In addition, men whose calorie intake was less than 800 calories per day or more than 4200 calories per day were excluded, as were men who failed to answer more than 70 questions on the 131-question diet questionnaire.
In 1986, 1990, and 1994, the men also completed a food-frequency questionnaire (FFQ) that included information as to how often they consumed various foods and how much of these foods they consumed. Based on their overall scores on the FFQ, each man was ranked according to how his diet conformed to each of the two dietary patterns (prudent and western) on a scale of 1 (lowest) to 5 (highest). Each man was assigned to one of the five categories of prudent diet and to one of the five categories of western diet. For example, one man could be ranked in the lowest category (1) for prudent diet and in the highest category (5) for western diet.
In 1998—after 12 years of follow-up—the researchers compared the number of men in the highest category of western diet who developed type 2 diabetes with the number of men in the lowest category of western diet who developed type 2 diabetes. They made the same comparison between highest and lowest category of prudent diet. In other words, the men were assessed twice—once based on their rankings on the prudent diet scale and once based on their rankings on the western diet scale.
After accounting for other risk factors for type 2 diabetes, the results were as follows.
Within the western diet categories, the men whose diets ranked in the highest category were about 60% more likely to develop type 2 diabetes than men in the lowest category. Within the prudent diet categories, men whose diets ranked in the highest category were about 15% less likely to develop type 2 diabetes than men in the lowest category. However, the validity of this finding is weakened by the fact that it was not statistically significant.
The researchers also assessed how obesity and physical activity played into the association between diet type and the development of diabetes. Men who were the least physically active and were in the highest category of western diet appeared to be nearly 2 times more likely to develop type 2 diabetes than men in the lowest category of western diet who were the most physically active. Similarly, obese men in the highest category of western diet appeared to be 11 times more likely to develop diabetes than non-obese men in the lowest of category of western diet.
There are limitations to this study, however. First, the study subjects were all men and most were white, so it is not clear whether these findings will apply to women and people of other racial and ethnic groups. Second, though FFQs are considered fairly reliable indicators of dietary habits, they rely on the study subjects to recall their dietary habits accurately, which may not always be the case. Third, because the researchers based diabetes status on the questionnaires and medical records rather than testing all the subjects for diabetes, some subjects in the study may have developed diabetes that was not yet diagnosed.
Should you try to eat a diet that more closely resembles the prudent diet than the western diet?
Absolutely! Although this study suggests that a prudent diet may reduce your risk of type 2 diabetes, it's also likely to reduce your risk of heart disease, stroke, and certain cancers. The findings of this study also provide more evidence that obesity and lack of physical activity can increase your risk of type 2 diabetes. So in addition to gradually changing your eating habits, don't forget about the benefits of regular exercise and weight management.