healthHealth and Medicine

Harvard Professor Says This Kind Of Diet Would Cut Preventable Deaths By A Third


Robin Andrews

Science & Policy Writer


There's no consensus right now on whether vegetarians live longer or not. Foxys Forest Manufacture/Shutterstock

A researcher from Harvard University has come to the conclusion that vegetarian diets may help you live longer. Saying that, a major study back in 2015 came to an altogether different conclusion: Sure, plant-based diets can be healthy, but they probably don’t help you live longer.

So – what’s the deal?


First off, these latest revelations aren’t based on a single, new study, but the words spoken by one Professor Walter Willett, an epidemiologist and prolific nutrition expert at Harvard University’s T.H. Chan School of Public Health. He was an invited speaker at this week’s Unite to Cure Fourth International Vatican Conference in Vatican City, and here’s what he had to say, courtesy of the Telegraph:

“We have just been doing some calculations looking at the question of how much could we reduce mortality shifting towards a healthy, more plant-based diet, not necessarily totally vegan, and our estimates are about one-third of deaths could be prevented,” he said, presumably referring to premature deaths.

“That’s not even talking about physical activity or not smoking, and that’s all deaths, not just cancer deaths. That’s probably an underestimate as well as that doesn’t take into account the fact that obesity is important and we control for obesity.

“When we start to look at it we see that healthy diet is related to a lower risk of almost everything that we look at.”


It's worth noting that Willett's comments don't actually use the word “vegetarian”, but rather reference a "healthy" and “more plant-based diet”.

“I didn’t refer to vegetarians for several reasons,” Willett told IFLScience. “First, the replacement issue is critical; if we replace red meat with soda, refined starch, and sugar, we will probably not be better off and might be even worse off.

“However, if we replace it with a mix of nuts, beans, soy foods, and whole grains, we will have lower risks of heart disease, diabetes, and total mortality,” he noted. 

Willett emphasized that this isn't about a “simple dichotomy between being a vegetarian or not,” but instead the continuously lower risks related to greater shifts to a plant-based diet, with "healthy food replacing animal-based foods."


When asked about the calculations referenced at the conference, Willett directs us to multiple pre-existing studies he's involved with (including these three papers, and more), adding that there's a large literature to back up said findings.

So what about that 2015 study? Well, that looked at data from two pre-existing studies involving more than 60,000 people. Comparing the mortality rates of those on a variety of diets, they found that there was no clear difference in mortality rates.

Other studies agree or disagree with this conclusion, and often note many confounding factors are likely influencing the data. In fact, Willett opined that the studies of vegetarians have in general not considered those aforementioned food group replacement issues sufficiently.

At present, however, there doesn’t yet appear to be a clear consensus that the vegetarian diet will help you live longer, even if research frequently suggests that they're generally healthier than meat-eaters.


Sure, the overconsumption of meat, like the overconsumption of anything, is bad for you. Diets should be nutritionally balanced and based on good science, and most rarely tick both or either of these boxes. The same, of course, applies to vegetarian diets; generalizing dietary benefits isn't all that sensible.

In any case, the UK’s National Health Service (NHS) has some excellent explainers for those wishing to try out a fully vegetarian diet. As with all diets, they offer notes of caution: For example, they explain that vegetarian sources of omega-3 fatty acids may not be as beneficial to your cardiovascular system as those obtained from oily fish.

Importantly, though, they emphasize the need to have a “healthy, balanced diet”.

Like all diets, vegetarian or no, if you’re thinking of making a change, talk to your doctor first.


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