Health aspects of various digestible carbohydrates

Abstract

The present review adresses the question whether simple and complex carbohydrates may result in different physiological responses with emphasis on glucose tolerance, human energy metabolism, and blood lipid spectrum. Furthermore, the implications of possible different physiological responses are discussed in relation to diabetes mellitus, obesity, and cardiovascular disease. Previously, it was believed that all starches were digested more slowly than simple carbohydrates, resulting in a slower release of glucose into the bloodstream. The presumed higher insulinemic response of simple carbohydrates would eventually give rise to hyperinsulinemia and diabetes mellitus. At present, thinking in this area has changed and from many acute experimental studies it has become clear that there is a wide range of glycemic responses to both simple and complex carbohydrate foods, so that some complex carbohydrates give comparable glycemic and insulinemic responses to some simple carbohydrates. These responses to both forms of carbohydrates are appreciably influenced by certain other food components such as dietary fibre and antinutrients. Long(er) term studies on the relation between type of ingested carbohydrate and glucose tolerance show inconsistent results with two recent studies indicating a more beneficial effect of simple as compared to complex carbohydrates on glucose tolerance. Further long term well-controlled studies are necessary to elucidate this issue. Obesity develops under circumstances of a positive energy balance. Recent evidence indicates that energy balance can only be achieved in the case of macronutrient balance and that fat, protein and carbohydrate balances are regulated separately. Current literature indicates a closer regulation of carbohydrate than fat balance, and carbohydrates have been reported to have powerful effects on thermogenesis and energy intake. Differences in thermogenesis among simple carbohydrates have been reported with sucrose and fructose being more thermogenic than glucose. Also, a higher carbohydrate oxidation and more pronounced suppression of lipid oxidation have been reported with fructose ingestion as compared to glucose. Furthermore, it has been reported that there is no difference in the thermogenic efficiency with which the body handles simple and complex glucose saccharides. The implications of these results of acute studies remain uncertain since there is no evidence indicating differences in the effects of various carbohydrates on long(er) term energy and substrate balance. A change from a Western type of diet to a very high carbohydrate diet causes a reduction in HDL and LDL cholesterol but a possibly transient increase in plasma triglycerides. In early studies it was claimed that simple carbohydrates, especially sucrose or fructose, would have more adverse effects on blood lipid spectrum than complex carbohydrates. There is, however, no consistent evidence available to support such a presumption. In fact, the majority of studies indicate no difference in the effects of various types of carbohydrates on blood lipid spectrum when ingested in amounts comparable to habitual Western consumption patterns. Hyperlipidemias, obesity, hyperinsulinemia, insulin resistance, diabetes, and hypertension have all been implicated as risk factors for cardiovascular disease. There is no evidence to support an independent relationship between any of these factors and the consumption of simple carbohydrates. Taking the above considerations into account, it can be concluded that there is no evidence to implicate an independent role for simple carbohydrates compared to complex carbohydrates in the etiology of cardiovascular disease. The available literature indicates that there is no consistent evidence indicating differences in the effect of simple and complex carbohydrates on glucose tolerance, human energy metabolism and blood lipid spectrum. Furthermore, there is no evidence to implicate differences in the effects of simple and complex dietary carbohydrates in the etiology of obesity Diabetes Mellitus or cardiovascular disease.