Mr. Heisenbug says that smoking is the best predictor of heart disease. (Not quite. A high Agatston score is a better predictor. For example.) It is the best lifestyle predictor. People who smoke, according to this, have a six-fold increased risk of heart disease compared to non-smokers.
Why would this be? Heisenbug points to a study that found that when smokers quit, the microbial diversity of their gut increased. He speculates that (a) smoking decreases microbial diversity, which is quite plausible and (b) decreased microbial diversity increases heart disease — which has some plausibility.
It would be interesting to find other factors that have a big effect on microbial diversity and whether they are also associated with heart disease. The idea that smoking causes heart disease via its microbial effects predicts, or at least suggests, that a change that reduces microbial diversity a lot will increase heart disease.
The only lifestyle factor that we can safely say leads to a lack of microbial diversity is a diet that is low in fermentable fiber. And fiber intake is consistently linked (negatively) with heart disease. I’ve never seen data linking lower overall diversity to a decrease in risk for any disease. And lots showing the opposite.
The stuff about diversity (fiber intake increases diversity and is associated with less heart disease, many associations of more diversity with less risk of Disease X, no associations in the opposite direction) is substantial support for your idea, in my opinion.
His theory, in other words, made a prediction that turned out to be correct. A large fraction of what we’re told about health hasn’t led to any correct predictions. Here is an idea about how to prevent heart disease, a major killer, that there is actually reason to believe. And Heisenbug can say whatever he wants, in contrast to a heart disease expert quoted, say, in the New York Times, who is under pressure to say certain things. So we can take what he says at face value.
I agree. Especially because there’s never been a good explanation WHY fiber has that effect on [he means "association with" -- Seth] heart disease.
Suddenly I am a lot more interested in microbial diversity and the association of fiber and heart disease. Smoking has countless health effects — it increases many cancers, for example. Obviously it increases lung and throat cancer. This means there are many ways it could cause heart disease. Fiber is quite different than smoking and as far as I know has no effect on lung and throat cancer. If it could be established that fiber causes a reduction in heart disease (not just is associated with a reduction), that would be considerable evidence (but far from proof, of course) that microbial diversity influences heart disease.