Carbohydrates and health

Currently roughly half of the daily energy of the human diet is derived from dietary carbohydrates and thus carbohydrates have large public health potential. Recently, the role of dietary carbohydrates in human health has aroused a worldwide public debate. Traditionally, diets high in complex, fiber-rich, carbohydrates have been considered to be protective against various chronic diseases such as cardiovascular diseases (CVD), cancer, type 2 diabetes and obesity. Contrary, it has been suggested that diets high in rapidly absorbed carbohydrates, for example using as glycemic index (GI) or glycemic load (GL) as markers of quality, may cause dyslipidemia, hyperglycemia, insulin resistance, and other related metabolic disorders. Subsequently these can cause chronic diseases such as CVD, cancer and type 2 diabetes. The adverse effects seem to be the most evident among overweight, likely because of underlying metabolic abnormalities.

The concepts of GI or GL are example of simple tools used to categorize the food sources of carbohydrates based their rate of absorption. Carbohydrates that break down rapidly during digestion cause large increase in blood glucose concentration and have a high GI. In addition to quality, the concept of GL takes also into account the quantity of the carbohydrates.

In epidemiological studies diets high in GI and GL have been found to be related with increased risk of CVD and type II diabetes, although the findings are not consistent. For different types of cancer, the evidence is much more limited.

In our study, we found that both high GI and GL were associated with an increased risk of acute myocardial infarction (AMI) in those men whose BMI was ≥ 27.5 kg/m2. Among physically inactive men (energy expenditure for leisure-time physical activity was less than 50 kcal/d), high GL was also related with an increased risk of AMI. These findings support the hypothesis that high consumption of refined sources of carbohydrate foods may be detrimental to health in obese, who often have metabolic disorders such as insulin resistance.

GI and GL as tools to categorize the carbohydrate containing foods have also several limitations. GI and GL databases used in epidemiological studies are created based on small studies that have usually 10-20 participants. It is well known that variation in blood glucose response after consuming carbohydrate containing foods between individuals is high and may also vary significantly between days. Also food processing techniques, other components of a food, other concomitantly consumed foods affect to glucose response. Thus these databases, and GI and GL values as well, are only suggestive tool to assess the healthiness of a particular carbohydrate containing food. Most suitable these tools are when comparing various foods within food group, i.e. comparing e.g. different types of breads or breakfast cereals.

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