The findings of research published in the journal Appetite show that an observed increase in satiety after eating wholemeal breads was not substantiated by reduced energy intake at a subsequent meal, and the researchers maintain that the findings do not convincingly support a role in the regulation of energy balance for products made from wholemeal flours.
Wholegrain foods have received much attention in recent years, and have been proposed to play a role in energy regulation through lowering of postprandial glycemia and appetite.
Whole grains are found in products such as whole wheat, oatmeal, popcorn and brown rice. They consist of any grain that has retained its starchy endosperm, fibre-rich bran and its germ after milling.
The grains have also been shown to help reduce the risk factors for a number of diseases, including heart disease, cancer and diabetes.
The researchers explained how a randomized crossover single meal study in 16 young adults was conducted to test the effect of iso-caloric meals based on wholemeal wheat breads and pasta in comparison to similar refined wheat products on postprandial glycemia, appetite and energy intake (EI).
“All subjects were young, apparently healthy normal weight adults, with normal fasting glucose,” explained the authors.
Test meals consisted of either refined or wholemeal breads (heated for one minute in an oven) with cheese or refined or wholemeal pasta (boiled for 11 and 12 minutes without salt, respectively) with cheese and were served after an overnight fast.
The authors reported that all meals were served with 400ml of water, and that the breads were made specifically for the study by Barilla but the pasta products were commercially available products, also from Barilla.
The authors said that, on the meal test day, fasting blood glucose was measured twice and the subjects’ appetite sensation was assessed with a visual analogue scale (VAS), and the test meal was then consumed, for which the subjects’ were allowed a maximum of ten minutes.
Blood glucose was continuously measured and appetite sensation was assessed every half hour, they continued. The last blood sample was drawn 180 minutes after the test meal was consumed, and an ad libitum meal consisting of differently sized pizza slices with tomato sauce, ham and cheese (1060 kJ/100 g) together with 300 ml water was then served.
Food and water intake at this meal was registered and energy intake calculated, added the authors.
The scientists found that only the refined wheat pasta had a lower glycemic index compared to refined wheat bread, while wholegrain wheat bread but not wholegrain wheat pasta resulted in increased satiety and reduced hunger compared to refined wheat bread, but the Ad libitum EI score after the lunch meal did not differ.
Whole grain market
Demand is growing for wholegrain products in the UK and Ireland, with the number of launches of whole grain products in those countries increasing by a massive 500 per cent between 2002 and 2008.
Although this significant increase is characteristic of a market in its infancy, the figures are a good indication of sustained upward growth.
In 2002, Mintel’s Global New Products Database (GNPD) recorded four new products making a “wholegrain” claim launched in Ireland. In the UK, there were 29 product launches that year.
By 2008, these figures had increased to 24 and 171 respectively. In 2009 to date, there have been 10 whole grain product launches in Ireland and 81 in the UK.
Published online ahead of print
Title: Wholegrain vs. refined wheat bread and pasta. Effect on postprandial glycemia, appetite, and subsequent ad libitum energy intake in young healthy adults
Authors: M Kristensen, M. G. Jensen, G. Riboldi, M. Petronio, S. Bügel, S. Toubro, I. Tetens, A. Astrup