Diabetes is Australia’s fastest growing chronic health problem and is the sixth leading cause of death. In 2008, total number of Australians with diagnosed diabetes was 1.015 million people.
There is strong epidemiological evidence from around the world to suggest that eating a variety of wholegrain foods is beneficial in the prevention and management of type 2 diabetes – this relationship is a consistent conclusion in systematic reviews.
Diabetes Prevention:
A Cochrane review published in 2008 concluded that high intakes of wholegrain foods reduce the risk of developing type 2 diabetes by 21-33%, a finding consistently demonstrated in the 11 cohort studies and one randomised controlled trial included in the review. The prospective studies also consistently showed an association between high intakes of wholegrain foods and cereal fibre, and reduced risk of type 2 diabetes, ranging from 27-30% and 28-37% respectively.
A study which followed 43,000 men for around 12 years found that those who ate the most wholegrain foods, including brown rice, oats, and barley, were less likely to be diagnosed with type 2 diabetes than those who ate the least. Those who ate the least wholegrain foods (around 0.2 serves per day) were nearly 30% more likely to develop type 2 diabetes compared with men who consumed the most – about 3.4 servings of wholegrains daily.
Since the Cochrane review, several other studies provide further supporting evidence. The MESA study of more than 5,000 US adults followed for seven years found a dietary pattern characterised by a high intake of wholegrains and fruit was associated with a 15% lower diabetes risk.
Wholegrains may in fact improve the way the body handles glucose. Comparisons of people without diabetes eating a white rice breakfast (control group) versus a group receiving a powdered breakfast made from coarsely ground wholegrains and legumes (powder group) found glucose and insulin responses following an oral glucose tolerance test (OGTT) were lower in the powder breakfast group. Individuals in the powder group relative to the control group also had less insulin resistance and improved beta cell function in the pancreas. GGHN – do you have a reference for this? Sourced from existing website, Diabetes page
In light of the evidence, The American Diabetes Association has made a specific dietary recommendation for individuals at high risk of diabetes – that being to consume half of their grain intake as wholegrain. Professor Jim Mann* has also acknowledged the role wholegrains play in diabetes prevention by stating “For those who are at risk but have not yet developed diabetes, the progression of impaired glucose tolerance to type 2 diabetes can be delayed, and insulin resistance improved, by lifestyle changes that include exercise and a diet that includes wholegrain foods.”
*Jim Mann is a Professor in Human Nutrition and Medicine at the University of Otago in New Zealand and Consultant Physician (Endocrinology) in Dunedin Hospital. Professor Mann is also the Director of the Edgar National Centre for Diabetes and Obesity Research (ENCDOR) and the WHO Collaborating Centre for Human Nutrition. His research has principally been in the fields of lipids and carbohydrates as they relate to coronary heart disease and diabetes and in the field of obesity. GGHN – please check you are permitted to add this info to the website.
Diabetes Management:
Wholegrain and high-fibre cereal foods can also help in the management of people who already have diabetes. A review of 24 studies that incorporated wholegrain foods into dietary interventions in subjects with type 2 diabetes found that, in all but two, there were improvements in glucose metabolism, including a reduction in insulin or oral hypoglycaemic agents, lowering fasting blood glucose, lowering glycosylated protein concentrations and reduced urinary glucose and C-peptide.
When testing insulin sensitivity in overweight people with type 2 diabetes on diets that incorporate refined or wholegrains, wholegrain diets have been found to facilitate a greater rate of glucose infusion. Insulin-resistant adults with normal blood glucose levels following an exercise and diet intervention program with increased intakes of wholegrain foods have also been found to achieve weight loss and enhanced insulin sensitivity. GGHN – do you have a ref for these studies? Sourced from ‘Diabetes’ page of existing website. Maybe it’s just from the Venn and Mann paper?
Long-term dietary intervention studies confirm that diets incorporating frequent consumption of wholegrain foods can reduce the progression from impaired glucose tolerance to type 2 diabetes by up to 58%.
Improving Glycaemic Control and Insulin Sensitivity:
Epidemiological studies as well as dietary intervention and metabolic studies strongly support the suggestion that wholegrain foods improve glycaemic control and insulin sensitivity. In the MESA study, there were significant inverse associations between wholegrain intake (0.02 to 1.4 serves a day in the highest quintile) and fasting glucose (2.5%), fasting insulin (9%) and insulin resistance (9%).
In a weight loss intervention trial with overweight subjects at high risk of diabetes, those fed two serves of a wholegrain-based liquid diet product had significantly better improvement in insulin resistance than controls fed an inulin-based product with equivalent levels of dietary fibre.
Suggested Mechanisms:
While there are several plausible mechanisms by which wholegrain foods might reduce diabetes risk and improve glycemic control, some uncertainties remain.
Insoluble Fibre: The evidence that wholegrain foods and insoluble dietary fibre derived from cereals protect against type 2 diabetes is strong and consistent among prospective studies. It is possible that this protection is afforded by the intact structure of the cereal grains slowing digestion and partially restricting absorption of the glycemic carbohydrate.
Nutrients: Long-term diabetes prevention benefits might also relate to the nutrient content of wholegrains. The strongest evidence of this is linked to the higher magnesium content of wholegrains, with prospective studies suggesting that low magnesium intake and status predates the diabetic condition.
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