Does Veganism Cause Strokes?

You may have seen the study a few weeks back featuring, among other things, the finding that vegetarians — vegans included — may be at a higher risk of stroke compared with meat-eaters.

If this is true, it presents a problem for us, but let’s back up a bit first.

I’ve noticed a knee-jerk reaction among some in the vegan community to studies like this. It’s automatically discounted as meat industry propaganda, scientists pushing an agenda, that sort of thing. This could be true — research involving diet and disease is rife with conflicts of interest, poor methods, and more. But it is not fair to come to this conclusion without digging a little bit deeper. Was the study actually funded by the industry? Is there an identifiable conflict of interest? Are the methods solid? It’s fair to raise these concerns if so, but if not, it just makes it look like we are unable to handle bad news. So let’s handle the bad news because it may not be so bad.

I also want to underscore the importance of actually reading the study, because unfortunately many people read an article summarizing the study which puts words in the scientists’ mouths. Journalists are typically not scientists, and they are often pressured to hint at conclusions that may not be supported by the evidence. Scientists, on the other hand, are supposed to be rigorous, deliberate with their words, and careful not to paint with a broad brush. I’ve seen some in the vegan community react to articles summarizing this study by arguing with the authors of the study, when really their gripe was with the reporter that inaccurately inferred causation.

The study looked at 48,188 participants from the United Kingdom with no history of heart disease. They were divided into three groups: meat-eaters (n = 24,428), pescetarians (n = 7,506), and vegetarians (including vegans; n = 16,254). They collected dietary information at baseline and then followed up years later, looking at the incidence of heart disease and stroke.

This means that, unlike other studies which use a cross-sectional design (i.e., collecting dietary patterns and history of heart disease or stroke at the same time, making causal inference quite difficult), this one is longitudinal: they looked at how people eat and what happened over time. While it still doesn’t allow us to definitively conclude a causal relationship, it can narrow things down much more than a cross-sectional design. Also, unlike other studies, this one features a rather large sample size.

One interesting finding in this study, totally unrelated to the main point: they found that vegans and vegetarians tended to be of lower class compared to meat-eaters:

Overall, non-meat eaters were younger and had a lower area level socioeconomic status than meat eaters, but were more highly educated, less likely to smoke, reported slightly lower alcohol consumption, were more physically active, and were more likely to report dietary supplement use.

That contradicts claims by many that veganism isn’t for the poor or that veganism is merely a privilege of the rich.

The researchers found that, over the course of the follow-up period, vegetarians — vegans included — had a lower risk of ischaemic heart disease, but not a statistically significantly lower risk of heart attack:

As seen above, the risk of haemorrhagic stroke and total stroke, but not ischaemic stroke, were significantly greater in vegetarians — including vegans.

Personally, I figured that something that increases your risk for heart disease or heart attack would also increase your risk for stroke, and vice versa, but this study challenged that assumption.

Notably, when they analyzed vegans and vegetarians separately, the significant associations relating to risk for heart disease and stroke disappeared; they attribute this to the relatively small number of vegans in their sample:

When we assessed vegetarians and vegans separately, the point estimates for vegans were lower for ischaemic heart disease (0.82, 0.64 to 1.05) and higher for total stroke (1.35, 0.95 to 1.92) than meat eaters, but neither estimate was statistically significant, possibly because of the small number of cases in vegans.”

While we can take some solace in the fact that this relationship was not statistically significant, we should be concerned that the estimate for the increased risk for total stroke (1.35, or 35%) is even higher than that for vegetarians including vegans (1.20, or 20%). However, the risk for heart disease among vegans was estimated to be even lower than for vegetarians (0.82, or 82%, versus 0.89, or 89%). Again, these are not statistically significant estimates so we need to be cautious about what conclusions we can draw.

As with many things, it’s not so black and white. We need to critically examine the evidence and not throw away that which we do not like. We also need to keep in mind that an increased risk for stroke among vegetarians including vegans is not a death sentence; it’s still unlikely to happen to any given person.

This is the sort of study that opens the door to further examination. This can help us greatly. Even if vegans are at a relatively greater risk than meat-eaters for stroke, we’re at a reduced risk for heart disease. Why is that? We could learn a lot from taking in the science and accepting it unless we have reason to do otherwise.

Perhaps zooming in on vegetarians and vegans could reveal that the increased risk for stroke is due to, say, B12 deficiency. B12 is cheap and easy supplement that every vegan should take anyway; if that’s all it takes to reduce our risk of stroke to be on par with meat-eaters, and retain our relatively reduced risk for heart attacks, that’s excellent news.

This is the sort of science we should welcome with open arms. Scientists aren’t trying to hurt us, and unless they truly are stooges of the meat industry, we should take their findings seriously and not presume malice on their part. We need to be confident in veganism as an ethical stance, and learn whatever we can from scientific findings that help us remain healthy.

After all, we can’t save animals if we’re dead.

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