Search:
Menopause Live - IMS Updates
InFocus

Date of release: 17 August, 2009

Vegetarianism and the risk of cancer


Vegetarianism is regarded by many as one of the best ‘eat healthy’ strategies. Epidemiological studies have shown that consuming a vegetarian diet is associated with lower levels of low density lipoprotein cholesterol and a smaller incidence of overweight, hypertension and type 2 diabetes mellitus compared to consuming a diet with meat [1]. Some studies have reported on better longevity in vegetarians as well [2]. Since dietary habits are often mentioned in regard to cancer risk, it became necessary to investigate large populations that consume specific foods. Vegetarians are, of course, a very good model for people with a well-defined nutrition characterized by a higher content of fiber, folic acid, vitamins C and E, many phytochemicals and a fat content that is more unsaturated. 


Key and colleagues have examined cancer incidence in a prospective study of 63,550 men and women in the UK and compared vegetarians to meat- and fish-eaters [3]. Participants, who were 20–89 years old, were recruited in the 1990s and followed until the end of 2005. When five types of malignant neoplasms were combined (lung, colorectal, breast, ovary, prostate), and meat-eaters considered as the reference point, fish-eaters had a 17% reduced risk (95% confidence interval (CI) 0.71–0.96) and vegetarians had an 11% reduced risk (95% CI 0.80–1.00) for cancer. However, the incidence of colorectal cancer was higher among vegetarians than in the meat-eaters. Interestingly, the number of cancer patients in this study was much lower than expected according to national rates. Among women, there were 27,652 non-vegetarians and 12,824 vegetarians. The relative risk for breast cancer was similar for all groups (fish-eaters 1.02, vegetarians 0.94) and was insignificantly lower for ovarian cancer (fish-eaters 0.43, 95% CI 0.18–1.01; vegetarians 0.73, 95% CI 0.42–1.28). Key and colleagues also published a pooled analysis from two prospective studies (including the above study) reporting on 20 cancer sites [4]. It was noteworthy that the risk for endometrial cancer was found to be insignificantly lower, and the risk for cervical cancer was insignificantly higher when fish-eaters and vegetarians were compared with meat-eaters.

Comment

Most reviews on breast cancer mention that a low-fat diet and energy restriction are associated with a reduced risk. In the current study, such a correlation was not found among vegetarians. Perhaps similarly, despite the common perception that meat-eaters have a higher risk for colorectal cancer than vegetarians, this was not found in Key’s British cohort. The key for understanding those findings may be hidden in the detailed nutritional characteristics of the subgroups inspected. It seems that the meat intake among the meat-eaters was only moderate compared to national figures from the UK. On the other hand, consumption of vegetables and fruits among the non-vegetarians was lower, but not so much different from that in the vegetarians.
Another specific sort of diet often investigated is the Mediterranean diet, a mixture of fish/sea food and vegetarianism. The diet is rich in vegetables, fruits, legumes, cereals, fish, and a moderate intake of red wine during meals. Greater adherence to a Mediterranean diet is associated with a significant improvement in health status, as seen by a significant reduction in overall mortality (9%), mortality from cardiovascular diseases (9%), incidence of or mortality from cancer (6%), and incidence of Parkinson’s disease and Alzheimer’s disease (13%) [5]. I believe that it is well established that diet has an important role in human morbidity and pathophysiology of various diseases. However, talking ‘headlines’ on vegetarianism, carnivores, Mediterranean diet, etc., may not necessarily apply to the individual because of the great variety in the exact contents of food among people who supposedly belong to the same category. Still, ‘eat healthy – be healthy’ is a good slogan that should be promoted.

Comentario

Amos Pines
Department of Medicine T, Ichilov Hospital, Tel-Aviv, Israel

    References

  1. Fraser GE. Vegetarian diets: what do we know of their effects on common chronic diseases? Am J Clin Nutr 2009;89(Suppl):1607-12S. Published May, 2009.
    http://www.ncbi.nlm.nih.gov/pubmed/19321569

  2. Singh PN, Sabate J, Fraser GE. Does low meat consumption increase life expectancy in humans? Am J Clin Nutr 2003;78(Suppl 3):526-32S.
    http://www.ncbi.nlm.nih.gov/pubmed/12936945

  3. Key TJ, Appleby PN, Spencer EA, et al. Cancer incidence in vegetarians: results from the European Prospective Investigation into Cancer and Nutrition (EPIC-Oxford). Am J Clin Nutr 2009;89(Suppl):1620-26S. Published May, 2009.
    http://www.ncbi.nlm.nih.gov/pubmed/19279082

  4. Key TJ, Appleby PN, Spencer EA, et al. Cancer incidence in British vegetarians. Br J Cancer 2009;101:192-7. Published July 7, 2009.
    http://www.ncbi.nlm.nih.gov/pubmed/19536095

  5. Sofi F, Cesari F, Abbate R, Gensini GF, Calsini A. Adherence to Mediterranean diet and health status: meta-analysis.BMJ 2008;337:a1344.
    http://www.ncbi.nlm.nih.gov/pubmed/18786971