Current recommendations are to consume more whole grains in order to prevent lifestyle disease such as diabetes, obesity and cardiovascular disease. Evidence in the nutritional literature has shown a benefit to increased whole grain consumption particularly with regard blood lipid lowering and fat loss effects. The accepted nomenclature of a whole grain product is however confusing, because as with all things, the food industry has used its powerful lobbying power to create a grey area that allows them to misapply labels to products. Whole grains should contain some of the original cereal grain in its original composition. That is to say there must be present the germ, endosperm and bran in its original ratio found within the unprocessed grain. However, a quick look at the breakfast cereal section of a supermarket shows that many products are called ‘whole grain’ which clearly contain little in the way of actual fibre or micronutrients.
True whole grains should actually contain whole grains. But these bitty products are unappealing to many and so food manufacturers grind the whole grain into a fine flour and mix small amounts with refined flour. That whole grains need to be present in the product for it to have beneficial effects on insulin has been demonstrated in research. For example, one group of researchers1 investigated the insulin response of healthy subjects to whole grains, cracked grains, course flour or a fine flour, consisting of the same original grain components. The results showed that insulin response was related to the wholeness of the grain, with the whole grains producing the smallest insulin response and the fine flour producing the greatest insulin response. Using an in vitro model, the researchers showed that starch hydrolysis of the grain products was related to the particle size. However, this was true only for wheat and maize, but was not true for oats.
These results therefore show that for whole grains to be effective at decreasing insulin response the whole grains must be partially intact. Whole grain products that do not contain intact grains may not be beneficial and should be avoided if health benefits are sought. Many breads on the market claim to contain both whole grain and refined flour and these products clearly contain no large whole grain particles and so in terms of preventing excessive insulin release are worthless. Similarly, breakfast cereal which no intact whole grains will not have significant insulin lowering effects. The benefits of whole grains derives from the inability of the starch digesting enzymes to penetrate the outer coat of the grains, and this slows digestion considerably. Grinding the whole grain to flour exposes the starch to amylase and increase digestion rates. This also explains the ineffectiveness of supplemental fibres when compared to ones of food origin.
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