Researchers at the university of California studied a group of 38,451 subjects from the Women's Health Study, aged 45 years or older at baseline, for seven years. They used a 131-item semi-quantitative food-frequency questionnaire at the start of the study to assess average dietary intake during the previous year.
Women with more than 70 blanks in the questionnaire, or those with a total daily energy intake of less than 2514 kJ or more than 14,665 kJ were excluded.
Glycaemic load was estimated for each woman by multiplying the glycaemic load for each food by the frequency of consumption and then summing up all foods.
The researchers identified 174 patients with incident colorectal cancer (148 with cancer of the colon and 26 with cancer of the rectum). The mean dietary glycaemic load for the cohort was 117, and the mean overall glycaemic index was 53.
"Dietary glycaemic load was statistically significantly associated with an increased risk of colorectal cancer and was associated, although not statistically significantly, with overall glycemic index," write the scientists in the 4 February issue of the Journal of the National Cancer Institute (vol 96, no 3, 229-233).
They conclude that a diet with a high glycaemic load could increase the risk of colorectal cancer by affecting insulin and insulin-like growth factors or, "as suggested by the cross-sectional association between dietary glycaemic load and C-reactive protein, by exacerbating pro-inflammatory responses, either locally or systemically." The researchers called for more research to be carried out to determine the mechanisms of the findings.
While low carbohydrate diets are currently all the rage in the US, Australian dieters are increasingly using the 'glycaemic index' (GI) to change their eating habits, and market analysts estimate that this trend could soon make an impact in Europe.
The GI is a numerical system of measuring how fast a food or ingredient triggers a rise in circulating blood glucose; the higher the GI, the greater the blood sugar response. A low GI food will cause a small rise in blood sugar levels, whereas a higher GI food may trigger a large increase.
Market research firm Mintel recently predicted that this type of carbohydrate control could soon take over the popularity of the low carbohydrate Atkins diet in the UK, where obesity affects a growing proportion of people. In response, UK company Reading Scientific Services (RSSL) said it can now offer a routine GI measurement service to ingredient suppliers and food product manufacturers.