Population studies have shown that whole grain consumption is associated with diminished risk of serious, diet-related diseases, which are major problems in wealthy industrialised economies and are emerging in developing countries with greater affluence. These conditions include coronary heart disease, certain cancers (especially of the large bowel), inflammatory bowel disease and disordered laxation. Carbohydrates are important contributors to the health benefits of whole grains. Insoluble non-starch polysaccharides (NSP, major components of dietary fibre) are effective laxatives. Soluble NSP (especially mixed-link ?-glucans) lower plasma cholesterol and so can reduce heart disease risk but the effect is inconsistent. Processing seems to be an important contributor to this variability and other grain components may be involved. However, starch not digested in the small intestine (resistant starch, RS) appears to be as important as NSP to large bowel function. Dietary analysis suggests that some populations (e.g. native Africans) at low risk of diet-related disease through consumption of unrefined cereals may actually have relatively low fibre intakes. While NSP are effective faecal bulking agents, they are fermented to a very variable extent by the large bowel microflora. In contrast, RS seems to act largely through the short chain fatty acids (SCFA) produced by these bacteria. One SCFA (butyrate) appears to be particularly effective in promoting large bowel function and RS fermentation appears to favour butyrate production. Animal studies show that dietary RS lowers diet-induced colonocyte genetic damage and chemically-induced large bowel cancer which correlates with increased butyrate. These effects could contribute to a lower risk of cancer and ulcerative colitis in the long term. Cereal grain oligosaccharide (OS) may also function as prebiotics and increase the levels of beneficial bacteria in the large bowel. Understanding the relationships between NSP, RS and OS and large bowel health will be facilitated by the advent of new molecular technologies to identify the bacterial species involved. The potential for improvements in public health is considerable.
Cereal Complex Carbohydrates and their Contribution to Human Health
Topping, D. (2007). Cereal complex carbohydrates and their contribution to human health. Journal of Cereal Science, 46(3), 220-229. doi:http://dx.doi.org/10.1016/j.jcs.2007.06.004