You can go on any sort of diet for a short while and be “okay,” but eventually an unhealthy diet will catch up with you.
So asking if a vegan diet is sustainable long term is a good question.
I’m going to summarize the biggest potential health issues of a vegan diet on a longer time scale, as well as studies that look at this exact topic.
Reasons a Vegan Might Not Be Healthy Long Term
Not all vegan diets are equal, and it is indeed possible to become ill over a longer time period if you don’t plan yours well.
There are 3 main concerns when it comes to nutritional deficiencies:
- Vitamin B12
- Vitamin D
Let’s go through each one at a time.
Vitamin B12 Deficiency on a Vegan Diet
Vitamin B12 is incredibly important for a wide variety of neurological functions. In other words, your brain doesn’t work so good if you’re deficient in it.
Most meat eaters get plenty of B12 from animal products, but plants don’t have any in them.
So when you first go vegan, you have full vitamin B12 stores, and those can last you for years.
This is the only supplement that I believe every vegan should take to be on the safe side. There’s no harm in getting too much (within reason).
Vitamin D Deficiency on a Vegan Diet
A common deficiency in everyone is a vitamin D deficiency. But it’s even harder for some vegans to get.
Vitamin D is stored in fat tissue for about 4 months.
In most places, you can get a lot of sun during the summer and fall, and that will more or less last you through the winter (you’ll still get some during the winter).
But in places that don’t get much sun, Nordic countries in particular, vitamin D deficiency is common.
A study in Finland found that:
In Finland, the dietary intake of vitamin D in vegans was insufficient to maintain serum 25-hydroxyvitamin D and parathyroid hormone concentrations within normal ranges in the winter, which appeared to have a negative effect on long-term BMD
The effects of a vitamin D deficiency might not be obvious right away, but they will show up in the long term.
The only substantial dietary sources of vitamin D are animal products (they also make vitamin D from the sun), but that’s not an option for vegans.
So, if you don’t get much sun, your best alternative is a vegan vitamin D supplement (ideally D3).
Iron Deficiency on a Vegan Diet
You can get plenty of iron on a vegan diet (legumes, grains, etc.), but it’s something that you need to pay attention to.
It’s also easy not to get enough, and to make things worse, iron from plants (non-heme) doesn’t absorb as well as iron from animal sources.
In order to avoid an iron deficiency, vegans need to pay attention to it and include good plant sources of iron.
If you’re not able to get enough from your diet, again, your only other option is to get a vegan iron supplement.
Studies Looking At Long Term Health of Vegans
A summary of this topic was recently done by the Cancer Epidemiology Unit from the University of Oxford.
They found that:
The long-term health of vegetarians appears to be generally good, and for some diseases and medical conditions it may be better than that of comparable omnivores. Much more research is needed, particularly on the long-term health of vegans.
There’s a lot of research showing that vegetarians are healthy long-term, but not very much specifically for vegans.
The research that is available for vegans typically has small sample sizes or isn’t over a long time period.
However, other studies seem to suggest that not only is a vegan diet healthy long term, but it’s likely healthier than one containing meat.
Another study found that:
More studies are also needed with long-term vegans because the health advantages appear more clearly defined when a person has been following a plant-based diet for >5 y
Again, more research needs to be done, but my point is that there are no obvious red flags as of now.
Summary: Can Vegans Be Healthy Long Term?
Obviously I’m vegan and probably biased.
But to me, there’s no logical reason to me a vegan diet wouldn’t be sustainable long-term in most situations.
However, according to the evidence, we can’t make any real conclusions right now.
What we can say (or speculate) is:
- Certain potential negative health effects of a vegan diet (i.e. deficiencies) may not show up for months or years.
- Vegans should test blood levels regularly (at least on a yearly basis).
- Vegans may need to use supplements for certain hard to get nutrients.
- While far from robust, the current research suggests that a vegan diet is probably even healthier than eating meat long term.
Unfortunately, we probably won’t get concrete answers to this question any time soon, so you’ll have to live what I’ve been able to find and summarize in this post.