The BBC: Be thin to cut cancer, study says
The Scotsman: Red meat increases cancer risk
The Independent: Consumers ignore cancer risks of eating red meat
The "scientists" carried out what was reported to be the largest ever inquiry into lifestyle and cancer, and issued several stark recommendations:
- Limit red meat
- Limit alcohol
- Avoid bacon, ham, and other processed meats
- No sugary drinks
- No weight gain after 21
- Exercise every day
- Breastfeed children
- Do not take dietary supplements to cut cancer
Well one thing to watch out for is the difference between association and causation. Lots of things can be associated with each other, but they do not necessarily cause each other. For example, if the sun rises at 6am and then my alarm clock goes off you could say that the sunrise and the alarm were associated....but the sunrise did not cause the alarm clock to go off. They happened at the same time but there was no cause/effect relationship.
Keep that idea in mind if you read the report. Anyway, I do not mean to go through the report, but suffice it to say that I think that we can be quite sceptical of its findings and recommendations.
There are three posts you need to read to get a handle on this stuff:
What’s the evidence cancers are our own fault? - a brilliant and exhaustive demolition of the poor science involved in this report, especially the confusion between correlation and causation. The post also explains how the report seems to ignore studies that do not support their position. For example with respect to red meat:
Here again, larger, stronger and newer studies were not included in this Report, including the largest meat study to date. For example, researchers at Harvard examined 14 studies on 725,258 people in North America and Europe investigating meat and fat and associations with colorectal cancer risk. As they reported in the Proceedings of the American Association of Cancer Research in 2004: “Greater intake of either red meat (excluding processed meat) or processed meat was not related to colorectal cancer risk.” This study was found nowhere in the list of references in this Report
Are the recent recommendations designed to ward off cancer justified? - Dr Briffa again talks about the difference between association and causation:
....... these recommendations come from what are known a epidemiological studies, which look for associations betweens things. Clearly, the panel has found a stack of evidence that links, say, excess weight with cancer. However, this link does not mean that one is causing the other.
Let’s for a moment imagine that a study finds that owning a television is associated with obesity. The question is, does owning a TV cause heart disease? Imagine you bought a TV but left it in its box and stored it in the attic. Would you be at increased risk of heart disease? Probably not. However, watching the TV endlessly for hours might be a problem. However, it’s not really owning a TV, but watching it and therefore being more sedentary that is the likely true cause of an enhanced risk of heart disease. It doesn’t matter whether we have 1 or a hundred such studies – they still cannot be used to impugn TV ownership, because we just don’t know that it is this or something associated with TV ownership (such as being more sedentary) that is the true cause of heart disease.
The same argument can be made for any association found in epidemiological studies, including those found between body weight and cancer.
He also notes that the study only looks at cancer, not other causes of death. If you don't get cancer you will die of something else anyway:
...again, the focus is on cancer. When we broaden the debate and focus on overall mortality rates, we find that these are not any higher in meat-eaters than vegetarians. In light of this, meat somehow doesn’t look quite so ‘deadly’.Does red meat really increase colon cancer risk? - we have been eating all of these meats for several thousands of years – without any history of colon cancer. Many peoples in the world still do. So why should they be carcinogenic now? Indeed the writer points out that when you look closely at some of these studies you find some odd things that the scientists and journalists do not really emphasise:
.......... red meat intake does not increase the risk in Aarhus and Potsdam (1.00 means no effect) and it is protective in Italy (0.96 means 4% lower cancer risk in relative terms). ....So in some countries eating red meat seems to be harmful, in another it is beneficial, and in yet more it has no effect one way or the other!
I know it winds some people up, but I'd still come back to the question of what were we designed for. We have been eating red meat for millennia. It is full of nutrients that are often unavailable elsewhere. I am not planning to cut back!
We need to be a bit sceptical about all this science!