Wednesday, August 11, 2010


Even epidemiologists agree that evidence on meat intake and breast cancer is inconsistent and marginal at best. This is an understatement since if you look carefully at their data there is no convincing evidence that any significant relationship exists. But, as usual they are going to try again and in Ferrucci et al.(2009) British J. Cancer 101, 178 they state that they have shown an elevated risk of breast cancer associated with eating red meat.

But, as usual, I have actually examined their data and it just isn’t so. The following figure shows the hazard ratio (similar to a relative risk) and confidence intervals for five groups of women (age 55-74) based on the amount of red meat they consumed.

Group 1 consumed the smallest amount of meat and 5 the most. So you would expect to see an increase in risk as the amount of red meat consumed goes up,- if eating red meat is related to risk. Which as you can see it is not. The response line is flat and the CIs include the no effect level of 1 with the exception of group 2. Since the women in group 2 are consuming much less meat than groups 3-5 this value is a statistical fluke.

This is one of those papers which contains the actual number of cases of breast cancerper number of person years in each food intake group. Thus, an actual percent can be calculated and these are presented in the following table.

So the actual percent difference between group 1 and group 5 is 0.05% or 5/10,000 which is a very small number and would not be considered to be of any statistical or biological significance.

Well if red meat was not going to show an increase the risk of breast cancer maybe other categories will. So they examined:

1. Steak: No increased risk

2. Hamburger: No increased risk

3. Sausage: No increased risk

4. Bacon: No increased risk

5. Pork chops: No increased risk

6. Processed meat: No increased risk


Try as they might there is no evidence that red meat and other kinds of meat increase the risk of breast cancer.

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