The Role of Fruits and Vegetables in Diabetes
Intake of fruits and vegetables, and prevention of type 2 diabetes
The increase in the incidence of type 2 diabetes has been attributed in part to high-fat, high calorie diets, overweight and obesity - particularly excess abdominal fat, and lack of exercise(1,2). These factors are associated with insulin resistance and metabolic syndrome- important risk factors for type 2 diabetes and cardiovascular disease(3). Estimates suggest that up to a 75% reduction in risk for type 2 diabetes could be achieved by preventing obesity(4).
Observations from population-based studies suggest that fruit and vegetable consumption may be associated with a reduced risk of diabetes(5-8) or may be protective(9), although results have not always been consistent(10-12). A positive association between fruits and vegetables and reduced risk is supported by an inverse association between serum carotenoids, a marker for fruit and vegetable intake, and type 2 diabetes and impaired glucose metabolism in adults(13).
Dietary patterns that include fruits and vegetables have been associated with a reduction in fasting blood glucose(14-16), improved results on glucose tolerance tests(17,18) lower glycosylated hemoglobin values(19) and enhanced insulin sensitivity(20). However, energy intake may modify these associations(21). Taken together, these studies suggest that fruit and vegetable intake is potentially beneficial for prevention and management of diabetes.
Fruits and vegetables and weight management
The relationship of obesity and type 2 diabetes is well established(22). Further, weight reduction is an integral part of treatment for type 2 diabetes, leading to improved glycemic control and often a reduction or elimination of the need for medication(22). Weight management may also minimize the increased risk of people with diabetes for cardiovascular diseases.
Research suggests that advice to increase intake of fruits and vegetables coupled with advice to decrease energy intake is an effective recommendation for weight management(23-25), as they are less calorically dense and more nutrient rich per serving than many foods(26).
Fruits and Vegetables, Fiber and Glycemic Control
Results from studies that have evaluated fiber and blood glucose control are inconsistent. Large amounts of fiber appear to be necessary for beneficial effects on glycemia, hyperinsulinemia and plasma lipids in people with diabetes. A recent study(27) addressed the potential issue of acceptability of a high fiber diet. In a randomized, crossover study, 13 patients with type 2 diabetes consumed a standard ADA diet (24 g total fiber) or a high fiber diet (50 g total fiber), achieved by including fruits and vegetables and grains, especially those high in soluble fiber. Results indicated that the high fiber diet improved glycemic control compared to the ADA diet, and patients accepted the high fiber diet with few side effects.
The fiber content of fruits and vegetables may also contribute to a lower glycemic index and hence glycemic load of the diet. A recent metaanalysis indicates that the use of this technique can provide an additional benefit over that observed when total carbohydrate is considered alone(28). Although scientists worldwide do not agree that using the glycemic index is the best way to plan carbohydrate intake for individuals including those with diabetes(29,30), the potential health benefits of fruits and vegetables for those with diabetes are becoming obvious.
Fruits and vegetables, antioxidants and diabetic complications
Newer research is revealing additional benefits of fruit and vegetable consumption for health in diabetes. Elevated blood glucose levels can lead to oxidative stress. This damage may play an important role in the development of complications in diabetes, such as lens cataracts, kidney disease and neurological disease(31). Animal studies suggest the mechanisms by which antioxidants in the diet may help counteract this damage(32). Data from the Third National Health and Nutrition Examination Survey (1988-1994) (NHANES III) showed that adults with metabolic syndrome have suboptimal concentrations of several antioxidants in the blood, as well as a lower consumption of fruits and vegetables compared to adults without metabolic syndrome(33). Further research is needed to determine the role of antioxidants for improving glycemic control and/or exerting antioxidant activity.
Overall the body of evidence strongly supports that healthy diets which include ample fruits and vegetables, whole-grains, and high-fiber foods without excess fat or calories, in conjunction with regular physical activity—can improve control of blood sugar among individuals with type 2 diabetes and may offer some protection against its development.
- Chan JM, Rimm EB, Colditz GA, Stampfer MJ, Willett WC. Obesity, fat distribution, and weight gain as risk factors for clinical diabetes in men. Diabetes Care.
- Hanson RL, Narayan KM, McCance DR, et al. Rate of weight gain, weight fluctuation, and incidence of NIDDM. Diabetes. 1995;44:261-6.
- Wannamethee SG, Shaper AG, Walker M. Overweight and obesity and weight change in middle aged men: impact on cardiovascular disease and diabetes. J Epidemiol Community Health. 2005;59:134-9.
- Field AE, Coakley EH, Must A, et al. Impact of overweight on the risk of developing common chronic diseases during a 10-year period. Arch Intern Med. 2001;161:1581-6.
- Ishikawa-Takata K, Ohta T, Moritaki K, Gotou T, Inoue S. Obesity, weight change and risks for hypertension, diabetes and hypercholesterolemia in Japanese men. Eur J Clin Nutr. 2002;56:601-7.
- Colditz GA, Willett WC, Rotnitzky A, Manson JE. Weight gain as a risk factor for clinical diabetes mellitus in women. Ann Intern Med. 1995;122:481-6.
- Carey VJ, Walters EE, Colditz GA, et al. Body fat distribution and risk of noninsulin-dependent diabetes mellitus in women. The Nurses’ Health Study. Am J Epidemiol. 1997;145:614-9.
- Wannamethee SG, Shaper AG. Weight change and duration of overweight and obesity in the incidence of type 2 diabetes. Diabetes Care. 1999;22:1266-72.
- Sakurai Y, Teruya K, Shimada N, et al. Association between duration of obesity and risk of non-insulin- dependent diabetes mellitus. The Sotetsu Study. Am J Epidemiol. 1999;149:256-60.
- Mokdad AH, Bowman BA, Ford ES, Vinicor F, Marks JS, Koplan JP. The continuing epidemics of obesity and diabetes in the United States. Jama. 2001;286:1195-200.
- Mokdad AH, Ford ES, Bowman BA, et al. Prevalence of obesity, diabetes, and obesity-related health risk factors, 2001. Jama. 2003;289:76-9.
- Zaninotto P, Wardle H, Stamatakis E, Mindell J, Head J. Forecasting Obesity to 2010. London: National Center for Social Research, Department of Epidemiology and Public Health. 2006:52.
- Bergmann KE, Mensink GB. [Anthropometric data and obesity]. Gesundheitswesen. 1999;61 Spec No:S115-20.
- Schienkiewitz A, Schulze MB, Hoffmann K, Kroke A, Boeing H. Body mass index history and risk of type 2 diabetes: results from the European Prospective Investigation into Cancer and Nutrition (EPIC)-Potsdam Study. Am J Clin Nutr. 2006;84:427-33.
- Boeing H, Korfmann A, Bergmann MM. Recruitment procedures of EPICGermany. European Investigation into Cancer and Nutrition. Ann Nutr Metab. 1999;43:205-15.
- Riboli E, Kaaks R. The EPIC Project: rationale and study design. European Prospective Investigation into Cancer and Nutrition. Int J Epidemiol. 1997;26:S6-14.
- Gunderson EP, Murtaugh MA, Lewis CE, Quesenberry CP, West DS, Sidney S. Excess gains in weight and waist circumference associated with childbearing: The Coronary Artery Risk Development in Young Adults Study (CARDIA). Int J Obes Relat Metab Disord. 2004;28:525-35.