Am Fam Physician. 2008;78(9):1
Background: Metabolic syndrome is characterized by increased risk of type 2 diabetes, cardiovascular disease, and all-cause mortality, and it affects about one fourth of American adults. Metabolic syndrome is defined by abnormal values of at least three of the following risk factors: waist circumference, blood pressure, fasting blood glucose, high-density lipoprotein cholesterol, and triglycerides (see accompanying table). It seems to be more prevalent in persons who consume a "Western" diet, which is characterized by high intake of processed and red meats, refined grains, and fried foods. Diet components have been linked in cross-sectional and some prospective studies to individual conditions within metabolic syndrome, but the role of diet in the development of the syndrome has not been studied. To evaluate the relationship between diet and the incidence of metabolic syndrome, Lutsey and colleagues prospectively studied men and women enrolled in the Atherosclerosis Risk in Communities study over nine years.
| Diagnosis requires the presence of at least three of the followingrisk factors: |
| Waist circumference measured at the level of the umbilicusmen: > 40 in (102 cm); women: > 35 in (88 cm) |
| Triglycerides: ≥ 150 mg per dL (1.70 mmol per L) |
| High-density lipoprotein cholesterolmen: < 40 mg per dL (1.05 mmol per L); women: < 50 mg per dL (1.30 mmol per L) |
| Systolic blood pressure: ≥ 130 mm Hg or current use of antihypertensives |
| Diastolic blood pressure: ≥ 85 mm Hg or current use of antihypertensives |
| Fasting blood glucose: ≥ 100 mg per dL (5.6 mmol per L) or current medication use for hyperglycemia |
The Study: The study population included middle-aged men and women in four communities in North Carolina, Minnesota, Mississippi, and Maryland who were evaluated every three years between 1987 and 1998 for the development of atherosclerotic disease. At each follow-up examination, participants underwent fasting venipuncture and measurement of blood pressure and anthropometrics. Demographic data and personal habits were also reviewed. Dietary intake was assessed at baseline and at six years using an interviewer-administered food-frequency questionnaire.
Food and beverages from the food questionnaire were organized into 29 food subgroups and then into five major food groups (dairy, meat, fruits and vegetables, refined grains, and whole grains). Consumption in each group was classified into quintiles. Fried foods, sweetened beverages (including regular soda and juice), diet soda, nuts, and coffee were also recorded for individual analysis.
Results: The mean age of the participants at baseline was 53.6 years. After nine years, about 40 percent developed metabolic syndrome. Two main dietary patterns emerged: the Western diet and the prudent diet, which was associated with greater vegetable, fruit, fish, and poultry consumption. After adjusting for behavioral traits that might confound the results, those with the highest quintile of Western diet scores had an 18 percent greater risk of metabolic syndrome than those in the lowest quintile. The prudent diet was not associated with metabolic syndrome.
Among individual foods, hamburger, hot dogs, and other processed meats were more likely to be associated with metabolic syndrome. Diet soda intake was also strongly associated with an increased risk, whereas coffee and nut intake did not affect risk. Those in the highest quintile for dairy consumption had a lower risk of metabolic syndrome.
Conclusion: This prospective study confirms results from cross-sectional analyses that found, after controlling for other risk factors, the high fat, processed and refined grains, and red meat diet popular in the Western world is strongly associated with metabolic syndrome. The association between diet soda and metabolic syndrome deserves further evaluation. The authors conclude that continued research and public education about modifiable risk factors will be increasingly important as the prevalence of metabolic syndrome in the United States continues to rise.