Effect of LifeStyle on Colo-rectal Cancer: The Adventist Study

Epidemiologists and people interested in public health love longitudinal studies of large groups. Perhaps the best well known is the Framingham study, but the Adventists are not far behind and they have always been a group of interest because of their focus on 'healthy living' and the ~ 50% fraction of the group that are variations of vegetarian.

Recently a study came out that compared meat eating to non-meat eating Adventists. Overall the meat eaters had about a 25% greater risk of colo-rectal cancer. Impressive data I think, but much more impressive, and not highlighted in the media or even the study itself, is that Adventists as a group are at much lower risk of colo-rectal cancer than Joe American. I normalized the Adventist study group age demographics to match the general US population and found that Adventists as a group had ~ 55% less colo-rectal cancer. To put some perspective on that number, the aggressive colonoscopy screening instituted in the US this past decade has decreased colo-rectal mortality by about 30%. So lifestyle as practiced by a vegetarian Adventist is twice as effective as screening colonoscopy.

More generally -- and close but not exact:

• The Adventist lifestyle reduces the risk of colo-rectal cancer by about half
• Vegetarianism leads to a further 20% reduction in risk.

It is also very likely true that the decrease in incidence has the very nice additional benefit of pushing those cancers that do occur to older ages.

Abstract: Vegetarian Dietary Patterns and the Risk of Colorectal Cancers. - PubMed - NCBI

 

True so far as it goes, but this ~ 78,000 group of people spans North America. Can you think of a convincing reason why this group's findings would not be generalized ? Moreover, this study is in line with many others. One might be skeptical of the degree but the general findings are pretty mainstream.

You should also keep in mind that the trick to identifying important correlations is to otherwise match the two comparison groups. So the fact that this group are all Adventists helps improve the likelihood of the finding being true. The study methods look pretty sound to me as well, and they do a good job of factoring out the other leading or suspected risk factors.

 

^^Ahh, I missed the humor. Sorry. Point taken

Your comment about genetics is mostly not true. The risk factor remains, but the relative risk may change.

 

^^ One study I briefly skimmed compared IIRC all cause mortality between Adventist physicians and non-Adventist physicians and found similar outcomes. That does not surprise me at all, since both groups have similar lifestyles insofar as the important risk factors for preventable death is concerned:

• Little to no tobacco use
• Moderate or less alcohol
• Low rates of obesity and diabetes
• (relatively) non-sedentary

And while physicians as a group have considerably more meat eaters percentage wise than the Adventists, my experience at least is that they do not consume anywhere near the amounts of red meat and pig typical of average Americans. Again only from my experience, vegetarianism among physicians younger than 35 is 10 - 20%.

 

As a public health issue, the (by far) leading group of chemicals that cause harm are antibiotics. I don't mean side effects, I mean misuse and abuse that leads to resistant organisms and altered micro-environments.

As for carcinogens, they are actually way down on the list for the public at large. Individuals in specific industries excluded.

 

"natural."

 

I grabbed a snippet of an abstract for you that is pretty representative of the current state of prime suspects / ignorance depending on your point of view:

Processed meat intake may be involved in the etiology of colorectal cancer, a major cause of death in affluent countries. The epidemiologic studies published to date conclude that the excess risk in the highest category of processed meat-eaters is comprised between 20 and 50% compared with non-eaters. In addition, the excess risk per gram of intake is clearly higher than that of fresh red meat. Several hypotheses, which are mainly based on studies carried out on red meat, may explain why processed meat intake is linked to cancer risk. Those that have been tested experimentally are (i) that high-fat diets could promote carcinogenesis via insulin resistance or fecal bile acids; (ii) that cooking meat at a high temperature forms carcinogenic heterocyclic amines and polycyclic aromatic hydrocarbons; (iii) that carcinogenic N-nitroso compounds are formed in meat and endogenously; (iv) that heme iron in red meat can promote carcinogenesis because it increases cell proliferation in the mucosa, through lipoperoxidation and/or cytotoxicity of fecal water. Nitrosation might increase the toxicity of heme in cured products. Solving this puzzle is a challenge that would permit to reduce cancer load by changing the processes rather than by banning processed meat. ​

N-nitroso compounds are the leading candidates. Think smoked products most of all, and heavily processed products after that.