2012 meta-analysis on veg mortality and cancer incidence
A new meta-analysis on vegetarian mortality and cancer has been released (1). It found a statistically reduced rate for vegetarians in terms of ischemic heart disease mortality and cancer incidence. It did not find a difference for all cause mortality or stroke.
Comments I have added to Disease Rates of Vegetarians and Vegans on VeganHealth.org:
“Although the 2012 meta-analysis by Huang et al. (1) is more recent, it may not be as reliable as the 1999 meta-analysis [by Key et al.] because it includes a 1984 study on Zen priests (2) who were mostly semi-vegetarian and which used a standardized mortality ratio (comparing all the Zen priests to the greater population rather than comparing the “vegetarians” to non-vegetarians within the same group). The Heidelberg Study results were also included and its control group was semi-vegetarians, which means there were semi-vegetarians in both the “vegetarian” and “non-vegetarian” group in the 2012 meta-analysis; while this is not ideal, it should have biased the results against finding a beneficial effect of a vegetarian diet. In its favor, the 2012 meta-analysis includes data from EPIC-Oxford that was not available for the 1999 meta-analysis.”
There is a table with the confidence intervals at the link above.
Reference
1. Huang T, Yang B, Zheng J, Li G, Wahlqvist ML, Li D. Cardiovascular Disease Mortality and Cancer Incidence in Vegetarians: A Meta-Analysis and Systematic Review. Ann Nutr Metab. 2012 Jun 1;60(4):233-240. (Link)
2. Ogata M, Ikeda M, Kuratsune M. Mortality among Japanese Zen priests. J Epidemiol Community Health. 1984 Jun;38(2):161-6. (Link)
June 15th, 2012 at 5:20 am
Jack,
what did you meant with this :”It did not find a difference for all cause mortality or stroke”.
Do I miss something here? The abstract of the meta-analysis includes this:
“All-cause mortality in vegetarians was 9% lower than in nonvegetarians (RR = 0.91; 95% CI, 0.66-1.16)”.
June 15th, 2012 at 8:41 am
Peter,
The abstract was misleading because it listed findings that were not statistically significant. But if you notice, the final sentence of the abstract was, “Our results suggest that vegetarians have a significantly lower ischemic heart disease mortality (29%) and overall cancer incidence (18%) than nonvegetarians.” For a finding to be statistically significant, 1.00 cannot be within the 95% confidence interval (CI). In the case of the all-cause mortality, it’s not even very close to statistical significance.