Sorry, I should probably add a summary at the top of the article so people don’t have to read the details. Overall, there’s a strong case that vegetarians (including vegans) don’t have a significant difference in mortality rates between regular meat-eaters, other things being equal. Vegetarians (including vegans) appear to have a lower incidence of heart disease and vegans, especially, have a lower incidence of type 2 diabetes. This means that vegetarians are probably healthier while alive, but don’t necessarily live longer.

Nigel,

The Humane Research Council study on vegetarian recidivism was a cross-sectional study and had no limit on the length of time someone had to be vegetarian (or vegan) before they could qualify as an ex-vegetarian. In other words, if someone considered themselves to follow a vegetarian diet for one day, they would have qualified to be an ex-vegetarian for the survey.

On the other hand, cohort studies measuring disease rates in vegetarians are prospective studies that follow people through time and measure their disease outcomes. They usually require that someone be a vegetarian for some period of time. For example, the EPIC-Oxford study participants were given follow-up surveys approximately 5, 10, and 15 years after entering the study to verify their diet.

The authors state, “When we excluded data for participants known to have changed diet group at least once during follow-up, leaving data for 4270 deaths before age 90, there was no significant difference in risk between diet groups for all causes of death combined, as follows: low meat eaters, HR: 0.93 (95% CI: 0.85, 1.02); fish eaters, HR: 0.91 (95% CI: 0.81, 1.02); and vegetarians and vegans, HR: 0.92 (95% CI: 0.84, 0.99) compared with regular meat eaters.” They don’t indicate how many people went from meat-eater to fish-eater to vegetarian, or the other direction, or whether they tested to see if one direction impacted the results more than another.

The Vegetarian Resource Group conducted a prospective study among their members and found a high retention rate among those completing the follow-up survey, including, “One hundred percent of vegan males stayed vegan, while 83% of females stayed vegan.” We don’t know how well that extrapolates to other vegetarians, but it’s a stark contrast to the Humane Research Council’s study and used an arguably better methodology for determining recidivism rates (i.e., prospective instead of cross-sectional and based on people who presumably had some resolve in being vegetarian).

Nikita,

Good catch, it’s fixed. Thanks.