When nutrition experts review the same data and come to different conclusions we have to ask why?
Nutrition experts review scientific evidence for different reasons. On the one hand a review might be conducted during the development of healthy eating advice for the general public – this has occurred recently in Australia during the preparation of the new Dietary Guidelines. In the United States and Canada, another reason for reviewing scientific evidence is to apply for a health claim – a government-sanctioned claim for use on food packaging. Such claims are a boon to marketing and are highly sought after. Whatever the motive for a scientific review on a particular topic, the results should be pretty much the same. Evidence is evidence. But it doesn’t always turn out that way.
Nutritionists have embraced the concept of wholegrains with a passion claiming they are protective foods. But the evidence is inconsistent, which may be due to the methodology of the studies that have been undertaken so far. As the dietary fibres found in some grain foods are beneficial for bowel function and lowering blood cholesterol there is a case for basing cereal recommendations on fibre. Other aspects of the nutritional quality of cereal goods, such as nutrient density and glycaemic index are also relevant. Just recommending wholegrains is not enough.
When it comes to recommendations about grain foods the draft Australian Dietary Guidelines keep it simple: eat mostly wholegrain. The rationale is simple too: wholegrains are nutrient-rich and protective against a range of modern diseases such as cardiovascular disease, type 2 diabetes and obesity.
But is it true? How evidence-based is this advice?