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A study recently published in the European Journal of Clinical Nutrition has found strong evidence for the role of wholegrains in the prevention and management of diabetes (Venn & Mann, 2004). The study examined current epidemiological and experimental research and found that people who included three or more serves of wholegrains each day were 20-30% less likely to develop Type 2 diabetes. Authors also found that wholegrains can help control glycaemic responses, a key component of diabetes management. The authors concluded that promoting consumption of wholegrain foods, along with fruits, vegetables and legumes, is beneficial for the people with diabetes, and for the general population.
There are a number of epidemiological studies supporting the role of wholegrains in the prevention and management of diabetes, particularly Type 2 diabetes. A study by Liu, 2002, concluded that wholegrains have a much more favourable affect on glycaemic response than refined grain foods. The author encourages educators to differentiate between refined and wholegrain foods and to advise people to replace refined grain foods with wholegrain varieties. The study also supports the role of wholegrains to prevent and manage heart disease.
In a review of three studies which used food frequency questionnaires to examine the eating habits of 160 000 adults, it was found that the incidence of diabetes was 21-27% lower for those in the highest quintile of wholegrain consumers, even after adjustment for the healthier lifestyle habits found in this group. Additionally, fasting insulin levels and insulin resistance were lower in non-diabetic individuals who ate a diet rich in wholegrains, and glucose control also improved when diabetic individuals included wholegrains (Murtaugh et al, 2003).
A long-term study conducted by Montonen et al, 2003, looked at the development of diabetes amongst 4316 adults over a ten-year period. It found that those people with a high intake of wholegrains had a much lower incidence of diabetes than those people who did not eat wholegrain foods, even after taking into account confounding factors, such as BMI and age. A variety of mechanisms are suggested to explain this protective role of wholegrains, including the action of soluble and insoluble fibre, and nutrients such as Vitamin B6, magnesium and folic acid, of which wholegrains are a rich source.
McKeown et al, 2002, examined the association between wholegrain foods and several metabolic risk factors for Type 2 diabetes in the Framingham Offspring Study cohort. The authors found that wholegrain intake was inversely associated with body mass index (BMI), waist-to-hip ratio, total cholesterol, LDL cholesterol and fasting insulin levels. The study outcomes support the hypothesis that increasing wholegrain intake may reduce the risk of diabetes, and other disease states such as cardiovascular disease, by means of favourable affects on these metabolic risk factors.
An intervention study by Liese et al, 2003, directly assessing the affect of wholegrains on insulin sensitivity, found that higher wholegrain intakes were associated with increased insulin sensitivity. The study tested 1625 adults from a variety of backgrounds, who had normal glucose tolerance, impaired glucose tolerance or Type 2 diabetes. Insulin sensitivity was measured using intravenous-glucose-tolerance test, and wholegrain intakes were assessed using food frequency questionnaires. From the results, the authors concluded that increasing wholegrain intakes may decrease the risk of diabetes by positively affecting one of the underlying mechanisms, namely insulin sensitivity, associated with the development of diabetes.
Hallfrisch and Behall, 2000, have conducted further investigation into the mechanisms behind the protective effects of wholegrains on insulin and glucose responses. A number of factors were found to be responsible, including the composition of the grain, particle size, amount and type of fibre, viscosity, amylose and amylopectin content, form, amount and method of cooking. The authors provide some general guidelines about the effectiveness of different grains, but most strongly recommend replacing refined grain products with whole grain products, regardless of the variety of grain.
Because of the growing evidence supporting the role of wholegrains in the prevention and management of diabetes, encouraging wholegrains is now recommended as a core component of health promotion messages. A study published this year by Schulze and Hu, 2005, emphasises the need to encourage people to replace refined grain products with whole grains, as part of health promotion strategies for targeting diabetes. Along with physical activity, replacing saturated and trans fats with unsaturated fats, moderating alcohol consumption and maintaining a healthy body weight, including wholegrains has been identified as a crucial element in diabetes prevention.
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- Venn BJ, Mann JI. Cereal grains, legumes and diabetes. Eur J Clin Nutr 2004;58(11):1443-1461.
- Hallfrisch J, Behall K, Mechanisms of the effects of grains on insulin and glucose responses. J Am Coll Nutr 2000;19:320S-325S.
- Liese A, Roach A, Sparks K et al, Whole-grain intake and insulin sensitivity: the Insulin Resistance Atherosclerosis Study. Am J Clin Nutr 2003;78(5):965-971.
- Liu S, Intake of refined carbohydrates and whole grain foods in relation to risk of type 2 diabetes mellitus and coronary heart disease, J Am Coll Nutr 2002;21(4):298-306.
- McKeown N, Meigs J, Liu S et al, Whole-grain intake is favourably associated with metabolic risk factors for type 2 diabetes and cardiovascular disease in the Framingham Offspring Study. Am J Clin Nutr 2002;76(2):390-398.
- Montonen J, Knekt P, Jarvinen R et al, Whole-grain and fiber intake and the incidence of type 2 diabetes. Am J Clin Nutr 2003;77(3):622-629.
- Murtaugh M, Jacobs D, Jacob B et al, Epidemiological support for the protection of whole grains against diabetes, Proc Nutr Soc 2003;62(1):143-149.
- Schulze M, Hu F, Primary prevention of diabetes: what can be done and how much can be prevented? Ann Rev Public Health 2005;26:445-467.
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