A variety of scientific studies have suggested that whole-grain products contribute to a healthy diet and, in particular, may be beneficial for the prevention of heart disease, diabetes and some cancers.
As clear evidence is necessary before these messages can be promoted to the public, BRI Australia’s grain health communication campaign, Go Grains, which is supported by growers and the Federal Government through the GRDC, has commissioned a series of independent reviews of the medical literature. Rada Rouse takes a look at their first two reports, covering coronary heart disease and weight control Soon to come: grains and cancer, and grains and allergy.
Whole grains are good for the heart — and it’s not just because their fibre lowers cholesterol in the blood, research shows Stewart Truswell, Emeritus Professor of Human Nutrition at the University of Sydney, in a review of the world medical literature, found that scientific evidence supports claims that eating whole grain breads or breakfast cereals may reduce the risk of heart disease.
Four separate studies based on trials involving a total of 174,000 people in the United States and Finland published in the late 1990s showed that, as consumption of cereal fibre or whole grains increased, the incidence of coronary heart disease declined.
More than fibre at work
“Only a minor part of this apparent protective effect can be explained by the cholesterol-lowering effect of soluble fibre,” Professor Truswell concluded.
Since whole grain wheat-based foods like breads and breakfast cereals were associated with lower risks of heart disease, there is clearly more than just fibre at work.
“From the available evidence it appears that the effect of whole grains on heart disease is the result of the many different protective factors present in grains, including folate and vitamin E, rather than any single factor,” Professor Truswell said.
Vitamins and antioxidants
Professor Truswell cites several other possible heart-protective mechanisms of whole grain food consumption, including the action of folate, a B vitamin, in lowering plasma levels of homocysteine, a substance linked to heart attacks and stroke.
Other protective factors may be the levels of antioxidants — vitamin E, selenium and phenolic acids — found in the outer layers of grains.
Effects of grain-based foods on insulin and glucose responses may also be relevant.
Importantly, Professor Truswell said, some whole grain cereal products including mixedgrain breads (but not wholemeal), oatmeal and rye breads have a low glycaemic index, meaning that they precipitate only a slight rise in blood glucose and insulin levels.
So what is meant by 'whole grain’?
Professor Truswell says there is a need to develop a universal definition of ‘whole grain’. Few of the studies reviewed for his paper define the term, with only the famous US Nurses Study — which followed nearly 69,000 women for ten years — spelling out the detail.
In this study, whole grain foods included dark breads, breakfast cereals containing more than 25 per cent whole grain or bran by weight, wheat germ, cooked oatmeal, and brown rice.
Popcorn was also on the whole grain list.
According to Go Grains campaign manager Trish Griffiths, popcorn is a good example of a whole grain snack that is healthy (as long as consumers go easy on the salt and butter!).
Refined grain foods include cakes, white bread, pasta, muffins, biscuits, refined breakfast cereals, white rice, pancakes, waffles and pizza.
“When we’re talking about whole grain foods, we’re talking about foods which contain all parts of the grain — the endosperm, the bran and the germ,” she said.
“In Australia there is no definition of whole grain, and Go Grains is actually right now working on trying to define how much whole grain ingredients a food needs to have before it can be labelled ‘whole grain’.”
Consumers may still need quite some convincing to switch their bread preferences on health grounds: more than half of the bread sold in Australia is still white.
Program 1.1.1 Contact: Ms Trish Griffiths 02 9888 9600 email firstname.lastname@example.org