Many people claim that a vegan diet can not only help prevent cancer, but also reverse (or treat) it.
However, these claims often don’t come with sources backing them up.
I decided to do a bit of digging into the subject to find relevant studies.
I’ll summarize what I found here.
Vegan (and Vegetarian) Diets and Lower Cancer Risk
Most of the research done around vegan diets and cancer is about whether it affects the risk of getting cancer, not treating it.
They’re different things, although related.
We’ll start by summarizing these studies, and then look at studies around treatment after.
First, vegan diets do appear to help prevent cancer:
Vegan diet seems to confer lower risk for overall and female-specific cancer than other dietary patterns. The lacto-ovo-vegetarian diets seem to confer protection from cancers of the gastrointestinal tract. (Source)
It is important to note a few things:
- Most studies looking at plant-based diets look at vegetarian diets, which are linked to lower cholesterol levels, lower blood pressure, lower risk of type 2 diabetes, and lower risk of prostate and colon cancer. (Source)
- Vegan diets also seem to have the same effects, but a vegan diet needs to be properly planned in order to avoid certain nutrient deficiencies (vitamin B12, vitamin D, calcium, etc.). (Source)
- One possible explanation of how a vegan diet may prevent cancer is that plant-based proteins increase glucagon activity, leading to benefits like lower cholesterol and decreased IGF-1 activity, which in turn reduces risk of cancer. (Source)
- Specific foods that vegans typically eat more of, like soy, are linked to a decrease in prostate cancer risk. (Source)
While nutrition studies are almost always correlational (and don’t prove causation), the evidence is pretty one-sided that vegetarians and vegans have a lower risk of many prominent cancers.
But Can a Vegan Diet Be Used to Treat Cancer?
This is a separate question from whether or not a vegan diet can prevent cancer.
It might seem like common sense that if a diet can prevent cancer, it should be able to reverse it as well, but it’s a separate claim that needs to be proved.
Unfortunately, there’s not a lot of research on this. The majority focuses on the risk of getting cancer in the first place.
However, I did find some related research that I thought was interesting. Here are the highlights:
- It should be made very clear that any diet (including vegan diets) are not treatments by themselves. Conventional cancer treatment should always be the focus of any therapy strategy. (Source)
- One intervention study put one group of men with prostate cancer on a vegan diet (with the other serving as a control group). There were no adverse effects of a vegan diet. The study only looked at the feasibility of the diet, rather than specific effects. In other words, a vegan diet didn’t make things worse, but they didn’t assess whether it made things better. (Source)
- A study in mouse models (ironic and sad for studying vegan diets) found that methionine restriction (vegan diets are lower in the amino acid methionine than meat-containing ones), produced therapeutic responses in chemotherapy-resistant colorectal cancer. (Source)
Like I said, there’s nothing out there as of yet that really looks at the effect a vegan diet has on a cancer patient (it’s a hard thing to study to be fair).
However, the pieces above form a foundation that suggest that a vegan diet may help (not replace traditional therapy) treat cancer. More research will hopefully build upon that start.
Summary: Can Vegan Diets Treat Cancer?
Research strongly suggests that vegan diets have preventative effects on cancer.
And while it seems to make sense that it would also be a good diet if you actually have cancer, that’s yet to be proven.
Unfortunately, data looking at eating a vegan diet in actual cancer patients is very limited, and while there are a few signs it could be effective, it is far from proven in any way.
That’s about all we can say on the topic, there’s just no definitive conclusions we can draw.