We certainly hear a lot about this. The trouble is that what looked great in case-control studies seems to get disproved when the more comprehensive prospective studies are done. Or, maybe not.
My latest HND piece takes a critical look at a big study just published in the Journal of the National Cancer Institute. Many are touting the results of this work, indicating that fruits and vegetables have little if any effect.
One of the obvious problems with the study is that "cancer" is used as the endpoint, with no further breakdown as to the type of cancer. Inasmuch as lung cancer is a major form of cancer, and it is caused in 90 percent of cases by smoking, don't you think that this might skew the results a little bit?
What would the results have been if smokers who got lung cancer were left off the study? After all, no one is suggesting that eating fruits and vegetables will make up for the negative effects of smoking.
Moreover, it is well known that certain fruits and vegetables and protective against certain cancers. While it is easier to get data on "cancer" and "fruits and vegetables," my take is that such broad categories prove very little.
It's almost as if these sorts of studies, which inevitably show no (or very little) effect for healthier diets or supplementation, are purposely designed to come out this way. As it is, a bravura review article done by Christian Roberts and James Barnard (J Appl Physiol 98: 3-40, 2005) examined 424 references and found that there was a major effect of exercise and diet on chronic disease. Cancer is one of the conditions covered in that work.
This paper can be downloaded for free, by the way.
Barnard notes on his website that
I have been studying diet and exercise for over 40 years and am convinced that most of the health problems seen in the U.S. and other industrialized countries are the result of poor diet, a lack of regular exercise and exposure to hazardous chemicals.
I would quibble with him a bit on that "hazardous chemicals" item, since it has been over-hyped, but I would have to agree with the rest of his statement.