Science

Are Vegetarians & Vegans at Higher Risk of Stroke?

This post contains a video, which you can also view here. To support more videos like this, head to patreon.com/rebecca!

Transcript:

Oh no, a new study shows that “Vegan and vegetarian diet could increase stroke risk!” Okay everyone, throw away your Impossible Whoppers. I mean, don’t throw them away…throw them at me. I will take them. They’re too dangerous to just leave in a trashcan! What if your dog eats them?? Send them to me. Send them all to me. I will…dispose of them. Properly.

So yes, there WAS a new study with some news about vegetarian diets, but no, obviously this doesn’t mean that vegan or vegetarian diets are suddenly unhealthy. I say “obviously” but it’s not going to be obvious to people who see these headlines and just think, “oh well, I guess I’ll just keep eating all the meat I want then, no need to try to be healthy.” Which is why I’m here, to help you in case one of these people sees you eating vegetarian and wants to tell you about how you should just give up instead.

The research in question is a massive cohort study just published in the British Medical Journal. I’ve talked before about how great cohort studies can be — essentially, it means researchers look at a giant population of people and follow their health over a period of many years to see which ones develop a disease. It can show us correlation, like “people who ride bikes have less acne,” but it can’t show us causation, like “riding bikes gets rid of pimples.” That’s not a real example by the way. Unfortunately.

In this case, researchers looked at nearly 50,000 people from 1993 to 2001. They split them up by what type of diet they reported having: meat eaters, pescetarians like myself who eat fish but no other meat, and vegetarians and vegans in the last group. That’s unfortunate they had to combine them but they didn’t have enough vegans to look at them separately, so that’s something for a future study.

Sure enough, they did find that the vegetarian group had a very tiny increase in occurrence of one, and only one type of stroke: hemorrhagic stroke, which is the kind where a blood vessel bursts. They found that the vegans and vegetarians stood a total of 20% higher chance of stroke compared to the other groups.

So where’s the issue? Well, the researchers take great pains to point out the context: meat eaters actually had a 13% increased risk of ischaemic heart disease — that’s where a blood vessel is blocked off so the heart doesn’t get enough blood. About 85% of all strokes are ischaemic as opposed to hemorrhagic, which means when you look at the actual numbers (as opposed to the percentage increase), eating meat is much worse. Compared to meat-eating, vegetarian and pescetarian diets led to 10 fewer cases of ischaemic heart disease per 1,000 people over 10 years. But the increase in hemorrhagic stroke was equivalent to only three new cases per 1,000 people over ten years.

Talking about percentages when it comes to increased risk is so tricky that way! For instance, let’s say you have to pick one: do you want a 90% increased chance of dying in a car accident, or a 10% increased chance of getting heart disease? You can’t just go based on which percentage is higher. To figure it out, you need to know your actual risk of each thing. In this case, to completely oversimplify things, your risk of dying in a car accident is about 1 in 77. In a population of 1,000 people, that means about 13 people will die. Increase that by 90% and now about 25 people will die — an increase of 12 deaths.

Your risk of dying of heart disease, though, is about 1 in 4. So out of 1,000 people, 250 people will die of heart disease. Increase that by 10% and you now have 275 people dying — an increase of 25. If you just wanted to minimize your chance of death, you’d take the 90% increase of a car accident and maybe just walk everywhere you go.

As an aside, that math even surprised me. I threw out 90% and 5% as random ridiculous figures thinking I’d have to adjust them once I did the math but nope, heart disease really is that fucking deadly. It’s so deadly that you can’t even compare it to the thing everyone compares risk of death to, a la “you’re more likely to die in the car on the way to the airport than you are in a plane crash.”

So the fact is that overall, the most impactful takeaway from this study is that subjects who ate meat other than just fish were much more likely to develop heart disease than pescetarians, vegetarians, or vegans. However, that’s not much of a surprise, as many studies have shown this over the years. Also, it’s worth noting that we don’t know cause and effect, and so we don’t know if some other lifestyle choice that meat-eaters tend to make contributes to that figure.

That’s why the hemorrhagic stroke finding is more interesting. Vegans and vegetarians tend to be healthier people in general — they tend to be more mindful of what they eat since it’s not the default in our culture (this study was done in the UK), and they also tend to be more physically active. So it is interesting that despite the fact that vegans and vegetarians tend to be healthier, they have a slight increase in this one type of stroke. Why could that be? Well, this actually also fits in with other studies, including several Japanese studies the authors cite showing a possible link between lower consumption of animal products and higher risk of stroke.

The authors point out that it might be due to some vegetarians and vegans having very low cholesterol, or a lack of the vitamin B12 which is primarily found in animal products and is responsible for the health of your blood cells, among many other important tasks. It’s derived from animal products but vegetarians can get it from milk, cheese, and eggs, while vegans can get it in fortified foods like cereals — yes, unlike many supplements B12 is perfectly fine for humans to consume outside of where it’s normally found. The problem is that you need to pay close attention to what you’re eating to make sure you get it, and not everyone on a vegan or vegetarian diet knows how important that is. 

And of course, it may be something else entirely, like some lifestyle choice that tends to go along with being a vegan or vegetarian. More research will be needed to tease that out. 

So in the meanwhile, don’t use this study as an excuse to not reduce your meat intake — that will pretty much always be a healthy decision for you and the planet. Just make sure that if you’re vegetarian or especially if you’re vegan, you’re getting all your necessary vitamins and minerals. Oh and you should still send me Impossible Whoppers. Just because.

Rebecca Watson

Rebecca is a writer, speaker, YouTube personality, and unrepentant science nerd. In addition to founding and continuing to run Skepchick, she hosts Quiz-o-Tron, a monthly science-themed quiz show and podcast that pits comedians against nerds. There is an asteroid named in her honor.

Related Articles

Leave a Reply

This site uses Akismet to reduce spam. Learn how your comment data is processed.

Back to top button
Close