In my last post I wrote about cinnamon and how it seems to be useful for blood sugar balance, a factor that is important for overall health. I also wrote about how the glycaemic index and glycaemic load of food and meals can have an effect on the blood sugar (glucose) levels.
A very recent study (1) has found a link between the glycaemic index of the foods and the glycaemic load of the meals we eat and the risk of developing breast cancer. As previously mentioned, the links between diet and cancer are widely researched. The World Cancer Research Fund UK (WCRF UK), a charity dedicated to cancer prevention, estimate that lifestyle factors such as being overweight, eating an unhealthy diet and being inactive are responsible for about a third of all cancers in developed countries (2).
Gycaemic index and glycaemic load are terms used to characterise foods and diets based on their effects on blood glucose levels. Foods that release sugar quickly into the bloodstream have what is known as a high Glycaemic Index (GI), meals that favour a spike in blood sugar levels are said to have a high Glycaemic Load (GL). White bread, potatoes, processed/refined carbohydrates have a high glycemic index i.e. they tend to cause a rapid surge in blood sugar. Vegetables, whole-grain high-fibre carbohydrates, create a more gradual change in blood sugar levels and are considered to have a low glycemic index. For the classification of more food examples please visit the website ‘The Glycemic Index’, there you will find a database where you can search for specific foods and find out more about GI and health.
This recent study (1) took place in Sweeden and looked at data from 61,433 women who completed special food frequency questionnaires in the late 1980s. After around 17 years there were 2952 women who had developed breast cancer. Analysis of the date found that eating a diet with high glycaemic load was significantly associated with an increased risk of developing breast cancer.
When the data was further analysed: total carbohydrate intake, glycaemic index and glycaemic load were all positively associated with the risk of developing a certain type of breast tumour known as oestrogen receptor (ER+) positive/progesterone receptor (PR-) negative breast cancer (ER+/PR-). Women with the highest glycaemic index diet had a 44% increased risk of developing ER+/PR- breast cancer compared to women with the lowest glycaemic index diet. Women in the highest category of glyceamic load had an 81% increased risk of ER+/PR- tumours, and those with the highest carbohydrate intake had a 34% increased risk, compared to those in the lowest groups. (No associations were observed for ER+/PR+ or ER-/PR- breast tumours)
The investigators speculate that high-glycemic load diets may boost breast cancer risk by increasing concentrations of insulin and sex hormones in the body, which may contribute to the development and spread of breast cancer cells. The WCRF UK say that the relevance of GI and GL to cancer “might lie in the fact that the rise in blood glucose after a meal is closely linked to that of insulin, which apart from its crucial role in carbohydrate and lipid metabolism, is also one of a family of important growth factors (2)”. High blood sugar levels after a meal are also related to an increase in inflammation in the body.
A healthy, nutritious diet which is low in processed/refined foods and rich in vegetables, nuts/seeds, beans, pulses, unprocessed meats and fish (especially oily fish such as salmon, mackerel and trout), healthy fats, unrefined wholegrains will generally keep blood sugar levels stable. Including a source of protein with every meal is also important for blood sugar balance e.g. beans/pulses, unprocessed meat and fish, eggs, nuts/seeds. For more information on blood sugar balance please read my post on cinnamon which contains relevant links.
(1)Larsson SC et al. 2009. Glycemic load, glycemic index and breast cancer risk in a prospective cohort of Swedish women. International Journal of Cancer. 125: 153-157
(2)WCRF/AICR. 2009. Policy and action for cancer prevention. Food, nutrition and physical activity: a global perspective. Washington DC: AICR, 2009
Written by Ani Kowal
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- Refined carbohydrates linked again with increased risk of heart disease
- Women eating foods with a high glycaemic index could be increasing their risk for heart disease
- Review study finds that a healthy diet may help reduce the risk of breast cancer
- Dietary carotenoids linked to a reduced risk of pre-menopausal breast cancer
- Fish oil supplements associated with a reduced risk of breast cancer
