This week’s hot nutrition news in the UK concerns a study which assessed the relationship between meat-eating and breast cancer. ‘Red meat ups breast cancer risk’ was, essentially, the way this study was headlined in the media. The brevity of such titles will usually not tell the full story, so I decided to take a closer look at this study and its findings.
In this study, researchers at the University of Leeds in the UK assessed the diets and risk of breast cancer in almost 34,000 pre- and post-menopausal women over about 8 years [1]. Meat consumption and risk of breast cancer was assessed in all women. The researchers also provided data for premenopausal and postmenopausal women taken alone.
This distinction turned out to be important, because the results in pre-menopausal and postmenopausal women were very different indeed.
For instance, high total meat consumption (defined as more than 103 grams of meat a day) in pre-menopausal women was associated with a 12 per cent increased risk of breast cancer compared to eating none. On the other hand, low meat consumption (defined as less than 62 g of meat per day) was associated with a 32 per cent reduced risk of breast compared to eating none at all.
Also, looking at the intake of different types of meat, higher intakes of red meat, processed meat, poultry and offal were not associated with a statistically significant increase in cancer risk.
In post-menopausal women it was a different story. Compared to eating no meat at all, even low levels of meat consumption were associated with a 52 per cent increased risk of breast cancer. High meat consumption was associated with a 63 per cent increased risk. This association was strongest for red and processed meat, hence the headlines. Poultry eating, on the other hand, was not significantly associated with risk of breast cancer in post-menopausal women.
However, it should be borne in mind that this study was a ‘epidemiological’ in nature, and cannot therefore be used to conclude that eating red or processed meat ‘ups breast cancer risk’. Just because two factors are associated, doesn’t mean one is causing the other.
Now, this study did attempt to account for other factors which may explain differences in breast cancer risk including age, weight, activity and fruit and vegetable consumption. However, accounting for such ‘confounding’ factors can be an imprecise science. For instance, breast cancer may be influenced by other factors that were not ‘controlled’ for that might influence the apparent association between meat eating and breast cancer risk.
Those still keen to take a cautionary approach here may like to consider avoiding any over-consumption of red and processed meat. That does not mean, however, that these foods cannot take some place in a healthy diet, though.
A broader view of the influence of meat-eating on health can perhaps be had by looking at overall risk of death in vegetarians and non-vegetarians-eaters. When attempts have been made to control for confounding factors, there has been found to be no statistical difference in mortality in those eating meat compared to vegetarians [2].
References:
1. Taylor EF, et al. Meat consumption and risk of breast cancer in the UK women’s cohort study. British Journal of Cancer 2007;96:1139-1146
2. Key TJ, et al. Mortality in British vegetarians review and preliminary results from EPIC-Oxford. Am J Clin Nutr 2003;78(suppl):533S-8S
