Carbohydrates that tend to be disruptive for levels of sugar in the bloodstream (high glycaemic index carbs) can provoke disease-causing changes in the physiology and biochemistry in the body, including enhance inflammation (see here for more about this). The pro-inflammatory effect of high-GI carbs has important implications, because inflammation turns out to be a key underlying process in conditions such as cardiovascular disease (e.g. heart attack and stroke) and cancer.
Cardiovascular disease and cancer are but two conditions that have links with inflammation in the body. Others include infectious diseases (e.g. septicaemia, pneumonia, flu), diabetes, lung disease, gastrointestinal disease (e.g. stomach or duodenal ulceration) and kidney failure. Inflammation can cause debilitating disease and death too. Bearing in mind that high-GI carbs can increase inflammation, could they increase the risk of death from inflammatory conditions aside from cardiovascular disease and cancer?
That is essentially the question posed by a piece of research published this week in the American Journal of Clinical Nutrition . In this study, 1490 postmenopausal women and 1245 men aged 49 or older were followed over a 13-year period. Women eating relatively high-GI diets, compared to those eating relatively low-GI diets, were found to be almost 3 times more likely to die from inflammatory diseases (excluding cardiovascular disease and cancer). This association was not found in men, however. There was no association in either men or women between dietary GI and risk of cardiovascular death either. Previous studies, however, have found that higher-GI diets are associated with a 20-100 per cent increased risk of cardiovascular disease (see here).
Why the association between higher-GI foods and increased risk of death from inflammatory disease in women but not in men? The authors point to previous research which demonstrates stronger links between GI and things like inflammation, excess weight, metabolic syndrome and type 2 diabetes in women than in men. They also point out evidence which showed generally higher ‘antioxidant status’ in men up to the age of 75, which might afford men greater protection against the pro-inflammatory nature of high-GI carbs.
My lasting impression from this study is that it’s perhaps a good idea to keep inflammation in check in the long term. A decent intake of omega-3 fats might be one approach here, but so is eating a diet of relatively low glycaemic index and load. One often-used marker for inflammation in the body is a substance known as ‘C-reactive protein’ or ‘CRP’ for short. The authors of the study discussed here cited evidence linking the consumption of low GI/GL diets with lower CRP levels in healthy overweight individuals  as well as in individuals with type 2 diabetes.
1. Buyken AE, et al. Carbohydrate nutrition and inflammatory disease mortality in older adults. Am J Clin Nutr 23 June 2010 [epub ahead of print publication]
2. Pittas AG, et al. A low-glycemic load diet facilitates greater weight loss in overweight adults with high insulin secretion but not in overweight adults with low insulin secretion in the CALERIE Trial. Diabetes Care 2005;28:2939-41
3. Wolever TM, et al. The Canadian Trial of Carbohydrates in Diabetes (CCD), a 1-y controlled trial of low-glycemic-index dietary carbohydrate in type 2 diabetes: no effect on glycated hemoglobin but reduction in C-reactive protein. Am J Clin Nutr 2008;87:114-25