Many of you will be aware that red meat has some bas press again, this time because of a supposed link with an increased risk of breast cancer. A study published this week in the Archives of Internal Medicine has revealed, we are warned, that pre-menopausal women eating red meat are at an increased risk of breast cancer [1]. Yet, again, red meat is painted as a major dietary spectre that we consume at our peril. But before we swallow these research findings whole without thinking, my suggestion is that we take a deeper look at this study and its findings.
The study in question is what is known as an ‘epidemiological’ study ” where associations are looked for between certain factors as disease. In this case, the headline grabber was that red meat consumption is associated with an increased risk of breast cancer in pre-menopausal women.
However, just because two things are ‘associated’ doesn’t necessarily mean one causes the other. Many health conscious individuals deliberately reduce their consumption of red meat, while non-health conscious individuals tend not to. It could be, therefore, that those eating more red meat might be subject to other factors which are the true causes of their increased risk of breast cancer such as higher alcohol consumption and lower intake of protective foods such as vegetables. In the study in question, other risk factors for breast cancer such as these were not factored into the equation, which significantly weakens its findings.
Also, what the study actually found was an association between red meat and a certain type of cancer known as hormone ‘hormone-dependent’ breast cancer. Hormone-dependent cancers (those whose growth is stimulated by hormones such as oestrogen and progesterone) are not the only type of breast cancer. When all types of breast cancer were grouped together, the apparent association between red meat and breast cancer disappeared.
And there’s something else about the findings of this study which suggest that red meat has been unfairly incriminated (again). If we look at the detail of this study we find that for intakes of red meat up to five portions a week (which some might regard as quite a lot of red meat), there was no associated increased risk of hormone-dependent breast cancer. With intakes from about 5 ” 7 portions per week there was, however (risk increase was 42 per cent). And a statistically significant increased risk was also found for intakes higher than about 10 portions per week. But the curious thing is that for intakes of 7-10 portions of red meat a week, there was no statistically significant increased risk of hormone dependent breast cancer.
In other words, what this study appears to show is that at quite decent levels of red meat intake there is no increased risk. As intakes rise, though, the risk becomes significant. Oh, but hang on a moment, at even higher intakes any significant risk disappears (only to return at still higher intakes). Does this sound like convincing evidence to you?
And all this gets even less convincing when you consider the results of a review of several studies (not just one) which found no association between red meat consumption and breast cancer risk [2]. What’s even more bizarre about all this is that the research department that produced this review (The Harvard School of Public Health in the USA) also had a hand in the recent rubbishy piece of research that’s had all the press.
What is it about researchers that lead them to churn out this sort of research and feed it to the press? Were the researchers themselves really blind to the woeful deficiencies of this study? Did they perhaps not think of stressing the inconsistency of the results and the fact that they are not in keeping with the body of evidence in the area?
I’m not sure I know how or why this sort of thing happens. However, I do think it’s at least worth bearing in mind that scientific and medical publishing is a competitive arena, and there’s much kudos (and even funding) to be had from having an academic department that publishes regular, meaningful (supposedly) results. My suggestion is that some researchers might be better off, for all our sakes, concentrating on quality, rather than quantity.
References:
1. Cho E, et al. Red meat consumption and risk of breast cancer among premenopausal women. Archives of Internal Medicine. 2006;166:2253-2259
2. Missmer SA, et al. Meat and dairy food consumption and breast cancer: a pooled analysis of cohort studies. International Journal of Epidemiology 2002;31(1):78-85.
