|Red (meat) breast cancer alert!|
Well the truth is that we are dealing with yet another prospective epidemiological study which does not have the power to reveal causal links between parameter (a), in this case the dietary protein sources in early adulthood and parameter (b), which is the incidence of breast cancer.
The average ignoramus will still read the headlines as "red meat" causes cancer and think of poultry, fish, eggs, legumes, and nuts as "the cure". In contrast to the red meat intake which was associated with a 22% risk increase in the 2830 documented cases of breast cancer the scientists had been collecting and following for 20 years, the a higher intake of poultry, fish, eggs, legumes, and nuts was
not just unrelated to breast cancer, in postmenopausal women, a high poultry intake was even associated with a -27% reduced breast cancer risk.
|Energy intake and cancer risk expressed relative to lowest intake quintile for red meat (Farvid. 2014)|
Unlike the fooled readers of the press release, the researchers are obviously aware of the weaknesses of the study, in the discussion of the results, Farvid et al. point out that "potential limitations need to be considered":
- participants were predominantly white, educated US adults, they cannot determine whether our findings are generalizable to other race or ethnic groups
- dietary intake was assessed by food frequency questionnaires, some degree of measurement error is inevitably present, and thus to reduce measurement error they used the cumulative average of
multiple measurements in a sensitivity analysis
- residual confounders are always of concern in any observational studies; although they adjusted for a wide range of potential confounders for breast cancer, they still could not rule out the possibility that other unmeasured or inadequately measured factors have confounded the true association
- they only estimated the effects of substitution of legumes, poultry, and other protein sources for red meat on risk of breast cancer, when trials on dietary modification would be ideal to support these substitutions
- Farvid, et al. "Dietary protein sources in early adulthood and breast cancer incidence: prospective cohort study." BMJ 2014;348:g3437 doi: 10.1136/bmj.g3437