High insulin levels linked with enhanced breast cancer risk

A year ago I reported on some research which had found a link between elevated levels of a substance called C-reactive protein (CRP) and worse outcomes for women with breast cancer. CRP levels tend to be higher in individuals with insulin resistance (where insulin levels tend to be high but the tissues in the body are resistant to its effects). This association was probably the reason why one of the authors of this study recommended women with breast cancer take steps to reduce their insulin levels, though at the time I expressed doubt about her suggestion that the diet should be low in fat. If insulin control is the desired outcome, I suggest a diet low in carbohydrate.

Yesterday saw the on-line publication of a study which, again, suggests that insulin may be a provoking factor in breast cancer [1]. The study compared insulin levels in more than 800 women with breast cancer, and a similar number without the disease. Women with the highest insulin levels were found to be at a 46 per cent increased risk of breast cancer. However, the associated between insulin levels and increased risk of breast cancer was only found to be significant in women who did not use hormone replacement therapy.

When the results were re-analysed for only women who were not taking hormone replacement therapy, those with the highest insulin levels were found to be almost 2.5 times at greater risk of breast cancer compared to those with the lowest levels.

We don’t know from studies of this nature whether high insulin levels actually cause breast cancer. However, any causal link between insulin and breast cancer would be strengthened by evidence that links the eating of foods that tend to cause high levels of insulin with increased breast cancer risk. As it happens, there is quite a body of evidence to this effect. See here, here and here for examples.

To my mind there are plenty of good reasons for keeping insulin levels low in the body. For women, there is mounting evidence that reducing risk of breast cancer is one of them.


Gunter MJ, et al. Insulin, Insulin-Like Growth Factor-I, and Risk of Breast Cancer in Postmenopausal Women. Journal of the National Cancer Institute 2008 [epub 30 Dec]

2 Responses to High insulin levels linked with enhanced breast cancer risk

  1. Pasi 4 January 2009 at 3:24 am #

    High insulin also means high blood sugar and high oxidative stress, lots of free radicals that cause damage on cells that can become cancer.
    High insulin decrease apoptosis, the normal way that the body handles faulty cells.
    Cancer cells usually live of sugar because normally they dont have mitocondrias , so high blood sugar promotes their growth and IGF-I support their growht.
    I guess we have the cause of birth and growth here in these statements even if some chemicals, FFA and cortisol also support cancer.

    Keep up the good work!


  1. Donna - 7 February 2009


    While looking for information on dieting Saturday specifically low carbohydrate diet cause I found your blog post High insulin levels linked with enhanced breast cancer risk | Dr …. You really made some great points. Thanks for sharing that info….

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