Vegan Health Problems: A Science-Backed Summary


Some people say that a vegan diet is going to destroy your health.

Others say that a vegan diet will cure all your problems and make you a virtual superhuman.

Which one (if either) is right?

The issue with most of those posts is that they aren’t based on any actual scientific evidence. Some do, but it’s often cherry-picked either way.

And since this is a topic people are very passionate about (on both sides), people are fairly good at ignoring arguments that contradict their opinions.

Personally, I’m vegan. However, I’m vegan because of ethical reasons, not health reasons. I don’t care if a vegan diet is good or bad for health, in fact when I went vegan in the middle of a semi-professional soccer season, I fully expected my performance to suffer (although it didn’t).

So I’m going to go about this post the right way; Objectively.

You can literally follow the same unbiased approach by going to Google Scholar and searching for phrases like “vegan health effects.” (Don’t add terms like “positive” or “negative,” or you’ve already become biased).

This post is a summary of the several studies I read on this topic in case you don’t have the time or don’t want to read studies with technical wording.

It’s important to understand these, or else you may end up sick and feel like you can’t be vegan anymore.

The American Journal of Clinical Nutrition: Health Effects of Vegan Diets

The author of this study had no financial conflicts, which is something you should always look out for and keep in mind.

The paper reviewed all the evidence available at the time (2009). Here’s the main takeaway from it:

Vegans tend to be thinner, have lower serum cholesterol, and lower blood pressure, reducing their risk of heart disease. However, eliminating all animal products from the diet increases the risk of certain nutritional deficiencies.

Most literature supports that a vegan diet might actually come with health benefits (if done right). Keep in mind that there are usually a few significant confounding factors (i.e. people who are health conscious are more likely to go vegan).

The other part of that takeaway is that a vegan diet comes with a greater risk of nutritional deficiencies. I think that’s pretty expected from anyone that’s vegan. You have to focus on getting enough of certain nutrients at first until you’re comfortable with the diet.

In particular, the author found that the risk for deficiency is most common for:

If you actually become deficient in any of those nutrients, it will likely have serious health consequences. It’s especially important for children, as deficiencies can stunt their growth.

On a proper vegan diet, it’s not hard to get enough of these. However, if you’re considering adopting a vegan diet now, it’s important to be aware of these potential issues and address them.

But for the scope of this post, this is where we move on.

Effects of a Vegan Diet on Cancer and Heart Disease

Next up is this meta-analysis that looked at 96 studies about both vegan and vegetarian diets.

Here’s the main takeaway:

This comprehensive meta-analysis reports a significant protective effect of a vegetarian diet versus the incidence and/or mortality from ischemic heart disease (−25%) and incidence from total cancer (−8%). Vegan diet conferred a significant reduced risk (−15%) of incidence from total cancer.

Both vegan and vegetarian diets appear to reduce the risk of ischemic heart disease (which leads to heart attacks) and total cancer.

It’s hard to know right now whether this is because of detrimental effects of animal products, or positive effects of having easier access to nutrients like choline on a vegan diet, which are involved in heart health.

The vegan diet appears even more protective when it comes to cancer.

Note the percentages of the risk decreases (8-25%). These aren’t exactly huge, but they are significant.

The lifetime risk of developing cancer is just under 40% for males, and about 38% for females. So a 15% decrease for males would take it from 40% to 34%.

This is where some bloggers significantly mislead readers who don’t understand that the risk change is relative.

Moving on, a vegan diet is likely a bit better for heart disease and cancer if anything.

A Cross-Sectional Study of 71,751 Subjects

This was a huge study with a mean age of 59 years old that used data that was collected from 2002-2007.

Subjects completes a 204 item questionnaire.

It found that the mean BMI was lowest in strict vegetarians, while also being highest in non-vegetarians.

Again, there’s that confounding factor that people more conscious about their health are probably more likely to be a strict vegetarian (or vegan, which this study didn’t include).

But still, the results show that people with a vegetarian diet have healthy BMIs.

The Effects of a Vegan Diet on Gut Microbiota

While it’s a relatively new area of focus, it’s becoming clear that your gut microbiota affects all sorts of aspects of your overall health.

This meta review specifically looked at how the vegan diet might impact gut microbiota.

Again, the authors had no conflict of interest to declare, and here’s the excerpt we’re most interested in:

The vegan gut profile appears to be unique in several characteristics, including a reduced abundance of pathobionts and a greater abundance of protective species. Reduced levels of inflammation may be the key feature linking the vegan gut microbiota with protective health effects.

This study was really about seeing if there was a link between gut microbiota and the health effects (like the lower risk of heart disease and cancer we saw above) of a vegan diet.

The takeaway is that there is a significant change in gut microbiota, which appears to have a protective effect. So that could at least partially explain some of the other results we saw.

Conclusion: Is a Vegan Diet Healthy or Not?

Which of those first 2 types of people are right?

The ones who claim that vegan diets are the worst thing for your health, or the ones claiming it’s a panacea?

After going through these studies, I think it’s clear how people tell both types of stories:

  1. A vegan diet does increase the risk for certain important nutritional deficiencies, which can lead to very serious health issues.
  2. A vegan diet can also reduce inflammation, help people maintain a healthy BMI, and reduce chance of cancer and heart disease (all these likely overlap).

In reality, if you’re a level-headed person looking for an object view of the issue, the likely conclusion you will draw is that properly vegan diet will have a beneficial effect on health, if anything.

Beyond that, we can’t really say anything because there are too many individual factors for any particular person. Some claim a vegan diet cured their skin conditions like eczema, while others say it made them worse.

I’m not claiming it’s going to give you superpowers, and you likely won’t notice any big changes if you already ate pretty healthily before going vegan (like I did).

We also don’t have much data to look at when it comes to long term vegans (see “are vegans healthier than meat eaters“). While I personally can’t think of any issues that would pop-up, we don’t have evidence either way.

I’ve done my best to be as objective as possible, holding studies that we summarized to a high standard. My hope is that you come away from this with a reasonable, broad view of the health effects of a vegan diet.

About the author

Dale Cudmore

Your friendly neighborhood vegan from Toronto. Chemical engineer turned semi-professional soccer player and freelance nutrition writer. I've been vegan for years and try to make life easier for others by sharing what I've learned.

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