High carb diets again linked to increased risk of breast cancer

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Previously on this site (for example see here) I have written about the role that certain carbohydrate foods appear to have in the development of breast cancer. Foods that are disruptive to blood sugar (high glycaemic index) foods have been implicated here. Also when high GI foods are eaten in quantity, they tend to have what is known as high ‘glycaemic load’ (GL – calculated by multiplying the amount of carbohydrate in a portion by the GI and then dividing the result by 100). High GL diets have been implicated as a risk factor for breast cancer too.

A study just published has added further evidence suggesting that carbohydrate foods can increase a woman’s risk of breast cancer [1]. In this study, more than 61,000 women were followed for over a 17-year period. Overall, higher GL diets were associated with an increased risk of breast cancer (though higher carbohydrate and higher GI diets were not).

The researchers went on to look at the relationship between carb intake and different types of breast cancer. Breast cancer is usually ‘hormone dependent’ (hormones can trigger and drive the development of the tumour), and can express receptors to the hormones such as oestrogen and/or progesterone. The researchers found that cancers that express oestrogen receptors but no progesterone receptors had strong links with carbohydrate intake.

High carbohydrate, high GI and high GL diets were associated with an increased risk of this sort of breast cancer of 33, 44 and 81 per cent respectively. The authors conclude that their findings suggest that a high carbohydrate intake and diets with high glycaemic index and glycaemic load may increase the risk of developing oestrogen positive/progesterone negative breast cancer.

Breast cancer risk has been linked to higher levels of the hormone insulin (see here for more about this). When insulin levels go up, so can the levels of related substances known as ‘insulin-like growth factors’, and these have also been implicated in the development of breast cancer.

Conventional nutritional advice has encouraged us all to eschew fat and embrace the high-carb ideal. The problem is, that this may well be contributing to our disease burden, including with regard to breast cancer risk. A better diet, I suggest, would be one which is lower in carb. This diet might be more in keeping with the diet we evolved on. Meat, fish, eggs, nuts, fruit and vegetables (other than the potato) should form the core foods in the diet, I think. Interestingly, diets with higher animal foods in them have been linked with a reduced risk of breast cancer (see here)

Any real link here may not be due so much to some particular nutritional goodies animal foods have to offer. It might have more to do with the fact that the more such foods are eaten, the less tendency there is to fill up on carbs that have disastrous consequences for health.


1. Larsson SC, et al. Glycemic load, glycemic index and breast cancer risk in a prospective cohort of Swedish women. Int J Cancer. 2009;125(1):153-7

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