Hi Elizabeth, I’m the co-author of the piece linked above. You’re absolutely right we chose to focus on the omnivore-vs-vegetarian comparison, for a variety of different reasons. However, AHS-2 does have some comparisons between omnivores to vegans. From the abstract: “the adjusted hazard ratio (HR) for all-cause mortality in all vegetarians combined vs non-vegetarians was 0.88 (95% CI, 0.80–0.97). The adjusted HR for all-cause mortality in vegans was 0.85 (95% CI, 0.73–1.01)”. So depending on how strict you are being with statistical significance there’s somewhere between a small signal and no signal that veganism is better with respect to all-cause mortality than omnivorism.
I think AHS is the best data we’ve got on this topic, but I’d be cautious about over-interpreting it. In my mind the biggest criticism is that Adventists are generally more healthy than the typical American (they do a lot more exercise, avoid alcohol and tobacco etc), which leads to extremely pernicious selection bias. For example, it could be that a vegan diet is much healthier than an omnivorous diet if you are the kind of person who spends a lot of time worrying about your health generally, but the risk of getting the wrong nutrients is so high with a vegan diet that it is harmful to people who are not otherwise concerned about their health. So I’m not confident the very slight improvement in overall mortality from switching from a vegetarian diet to a vegan diet can be judged to be a real effect from AHS alone.
On the other hand, I think I would be confident enough in the AHS data to say that it shows that veg*nism does not entail a tradeoff on the ‘years of life lived’ axis. The most conservative reading of the data possible would be that a veg*n diet has no effect on years of life lived, and I think it is probably more reasonable to read the AHS study as likely underestimating the benefits a veg*n diet would give the average person. Obviously ‘years of life lived’ is not the same thing as ‘health’ so I’m not saying this is a knock-down argument against your main point—just wanted to contextualise how we were using the data in the linked piece.
Scott describes the study as functionally randomized because restrictions vary by church, which is indeed the closest I could possibly hope to get with a nutrition RCT. However the cohort description makes no mention of this, and the 7DA I talked to said that it wasn’t his experience: individual churches varied a little in their recommendations, but people within the same church varied a little in their choice of diet. This seems corroborated by the fact that meat eating is associated with ~every bad thing.
Also if I’m reading this correctly, the rank ordering of death rates is for women: pescatarian < lacto-ovo-veg <vegan < omnivore (lower is better) for men: pescatarian =~ vegan < lacto-ovo vegetarian < omnivore
I have several questions on how you did the statistics, would you be willing to talk more over email?
Ah sorry, I seem to have slightly misled you. The quote which you attribute to Scott is actually written by me and the co-author of an adversarial collaboration hosted on Scott’s old blog. I’m not the author of the Adventist Health Study linked, much that I wish I was!
If you have questions about the statistics in the adversarial collaboration I’d be more than happy to talk through the approach we used. If you have questions about AHS2, by all means let’s share the work of finding the answer but I can’t promise to be any more help than any other random person you’d pick off the street
Getting the paper author on EAF did seem like an unreasonable stroke of good luck.
I wrote out my full thoughts here, before I saw your response, but the above captures a lot of it. The data in the paper is very different than what you described. I think it was especially misleading to give all the caveats you did without mentioning that pescetarianism tied with veganism in men, and surpassed it for women.
I made the mistake of looking at the total of the 7DA health data and I’m both excited and overwhelmed. Are there papers you would recommend I prioritize, besides the AHS2 one? Is there anything on adventists with medical issues affecting digestion?
Hi Elizabeth, I’m the co-author of the piece linked above. You’re absolutely right we chose to focus on the omnivore-vs-vegetarian comparison, for a variety of different reasons. However, AHS-2 does have some comparisons between omnivores to vegans. From the abstract: “the adjusted hazard ratio (HR) for all-cause mortality in all vegetarians combined vs non-vegetarians was 0.88 (95% CI, 0.80–0.97). The adjusted HR for all-cause mortality in vegans was 0.85 (95% CI, 0.73–1.01)”. So depending on how strict you are being with statistical significance there’s somewhere between a small signal and no signal that veganism is better with respect to all-cause mortality than omnivorism.
I think AHS is the best data we’ve got on this topic, but I’d be cautious about over-interpreting it. In my mind the biggest criticism is that Adventists are generally more healthy than the typical American (they do a lot more exercise, avoid alcohol and tobacco etc), which leads to extremely pernicious selection bias. For example, it could be that a vegan diet is much healthier than an omnivorous diet if you are the kind of person who spends a lot of time worrying about your health generally, but the risk of getting the wrong nutrients is so high with a vegan diet that it is harmful to people who are not otherwise concerned about their health. So I’m not confident the very slight improvement in overall mortality from switching from a vegetarian diet to a vegan diet can be judged to be a real effect from AHS alone.
On the other hand, I think I would be confident enough in the AHS data to say that it shows that veg*nism does not entail a tradeoff on the ‘years of life lived’ axis. The most conservative reading of the data possible would be that a veg*n diet has no effect on years of life lived, and I think it is probably more reasonable to read the AHS study as likely underestimating the benefits a veg*n diet would give the average person. Obviously ‘years of life lived’ is not the same thing as ‘health’ so I’m not saying this is a knock-down argument against your main point—just wanted to contextualise how we were using the data in the linked piece.
Scott describes the study as functionally randomized because restrictions vary by church, which is indeed the closest I could possibly hope to get with a nutrition RCT. However the cohort description makes no mention of this, and the 7DA I talked to said that it wasn’t his experience: individual churches varied a little in their recommendations, but people within the same church varied a little in their choice of diet. This seems corroborated by the fact that meat eating is associated with ~every bad thing.
Also if I’m reading this correctly, the rank ordering of death rates is
for women: pescatarian < lacto-ovo-veg <vegan < omnivore (lower is better)
for men: pescatarian =~ vegan < lacto-ovo vegetarian < omnivore
I have several questions on how you did the statistics, would you be willing to talk more over email?
Ah sorry, I seem to have slightly misled you. The quote which you attribute to Scott is actually written by me and the co-author of an adversarial collaboration hosted on Scott’s old blog. I’m not the author of the Adventist Health Study linked, much that I wish I was!
If you have questions about the statistics in the adversarial collaboration I’d be more than happy to talk through the approach we used. If you have questions about AHS2, by all means let’s share the work of finding the answer but I can’t promise to be any more help than any other random person you’d pick off the street
Getting the paper author on EAF did seem like an unreasonable stroke of good luck.
I wrote out my full thoughts here, before I saw your response, but the above captures a lot of it. The data in the paper is very different than what you described. I think it was especially misleading to give all the caveats you did without mentioning that pescetarianism tied with veganism in men, and surpassed it for women.
I made the mistake of looking at the total of the 7DA health data and I’m both excited and overwhelmed. Are there papers you would recommend I prioritize, besides the AHS2 one? Is there anything on adventists with medical issues affecting digestion?