N° 34 | May 2009

Fruit and vegetable intake, C-reactive protein and the metabolic syndrome

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The metabolic syndrome is a cluster of metabolic risk factors in individuals. This syndrome is highly prevalent worldwide1, 3. Individuals with the syndrome are at greater risk of morbidity and mortality due to cardiovascular disease and diabetes4, 5. The dietary determinants of this syndrome remain to be identified6, 7. Systemic inflammation, as measured by plasma C-reactive protein (CRP) concentrations, may directly affect cardiovascular disease through several mechanisms.

Fruits and vegetables associated with CRP levels?

Dietary intake of fruits and vegetables may reduce risk of the metabolic syndrome through beneficial combinations of antioxidants, fiber, potassium, magnesium and other phytochemicals. Fruits and vegetables have been associated with reduced risk of coronary heart disease but the mechanisms have not been well understood. Fruit and vegetable consumption may reduce the risk of coronary heart disease in part through lowering CRP. We conducted a crosssectional study, among 486 female teachers aged 40-60 y living in Tehran, to assess the association of consumption of fruits and vegetables with blood CRP levels and the prevalence of the metabolic syndrome.

A study in Tehran

Fruit and vegetable intakes were assessed using a validated questionnaire. Anthropometric measurements including weight, height, and waist circumference were measured and blood pressure was assessed according to standard methods.

Fasting blood samples were taken for biochemical measurements. Metabolic syndrome was defined as the presence of three or more of the following components8:

  1. abdominal adiposity (waist circumference >88 cm);
  2. low serum HDL-C (<50 mg/dL);
  3. high serum triglyceride levels (≥150 mg/dL);
  4. elevated blood pressure (≥ 130/85 mmHg);
  5. abnormal glucose homeostasis (fasting plasma glucose level≥110 mg/dL).

Fruits and vegetables consumption associated with lower risk of metabolic syndrome

The reported mean daily intake of fruits and vegetables was 228±79 and 186±88 g/d, respectively. The food items that contributed most to fruit intakes were apples, cantaloupe, watermelon, grapes and bananas, respectively; those that contributed most to vegetable intake were onions, tomatoes, mixed vegetables, lettuce, cucumber and green beans, respectively. Both fruit and vegetable intakes were inversely associated with plasma CRP concentrations. Individuals with higher intakes of fruits had lower plasma CRP levels as compared with those with lower intakes (1.56 vs. 1.94 mg/L).

This was also the case with vegetable intakes (1.47 vs. 2.03 mg/L). This inverse association remained significant even after additional control for dietary factors. Compared to those in the lowest quintile of fruit and vegetable intakes, individuals in the highest category had lower odds of having metabolic syndrome. Individuals in the highest quintile of fruits had 34% lower and those in the highest quintile of vegetables had 30% lower chance of having the metabolic syndrome9.

It is concluded that higher intake of fruits and vegetables were associated with lower risk of metabolic syndrome; part of this association may be mediated through CRP. These findings support current dietary recommendations to increase the intake of fruits and vegetables as a primary preventive measure against cardiovascular disease.

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  4. Hu G et al. Arch Intern Med 2004;164:1066-76.
  5. Scuteri A et al. Diabetes Care 2005; 28:882-7.
  6. Meydani M. Nutr Rev 2005; 63:312-4.
  7. Esmaillzadeh A and Azadbakht L. Diabetes Care 2008; 31: 223-226.
  8. National Cholesterol Education Program (NCEP) Expert Panel on Detection, Evaluation, and Treatment of High Blood Cholesterol in Adults (Adult Treatment Panel III). Third report of the national cholesterol Education Program (NCEP) Expert Panel on detection, evaluation, and treatment of high blood cholesterol in adults. Circulation 2002; 106: 3143-421.
  9. Esmaillzadeh A et al. Am J Clin Nutr 2006; 84: 1489-97.
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