An estimated 3 percent of Americans follow a vegan diet, not consuming any animal products at all; an additional 5 percent follow a vegetarian diet, eating eggs and dairy, but not meat. At the same time, Americans are eating more meat than ever. In 2020, we consumed an average of 265 pounds of meat per person, up from 97 pounds per person in 1999.
There are many reasons why people decide not to consume animal products. Some think it’s cruel to eat animals or believe our factory farming system is not sanitary. Others recognize the environmental impact of meat production, or choose a plant-based diet for their health.
What do we know about how plant-based diets affect our health?
For starters, it is important to understand that eating patterns are notoriously difficult to study. Most nutrition research is observational, which means researchers observe people who follow different diets over time without being able to account for other factors that may influence their health. Some vegetarians who choose plant-based diets out of health concerns may also, for example, be more health-conscious in other areas of their lives. Other vegetarians may choose a plant-based diet because a family history of heart disease, which may make them more likely to experience a heart attack or stroke. In addition, many nutrition studies require participants to self-report their food intake, which is not the most reliable way to collect data.
That said, there is a large body of evidence that demonstrates plant-based diets offer some health benefits.
A high-quality systematic review published in 2018 found evidence that eating a plant-based diet can help to manage Type 2 diabetes. This review is unique because most of the studies were randomized-controlled studies, the gold standard in research. The data showed that the participants eating a plant-based diet were better able to control their blood sugar and cholesterol levels and were more likely to lose weight compared with people who consumed animal products. In fact, many of the vegetarians in the studies were able to reduce the amount of medications they needed.
There is mixed evidence on whether plant-based diets help people to live longer. A study including more than 12,000 participants reported in the Journal of the American Heart Association found that plant-based diets helped people avoid heart disease and increased life expectancy. Meanwhile, another study of more than 250,000 participants conducted by Australian researchers found no difference in mortality rates among vegetarians and meat-eaters.
There is some solid data that plant-based diets contribute to a healthy gut microbiome—microorganisms in our digestive tracts that contribute to overall wellness. This is likely, at least in part, due to the amount of fiber in plant-based foods.
But there are still questions about whether plant-based diets contribute to cognitive health. A large systematic review in the journal Nature found the same health benefits identified in previous reviews: weight loss, better energy metabolism, improved gut microbiomes, and reduced likelihood of developing heart disease and diabetes. But researchers were unable to find evidence that plant-based diets help improve cognitive function and mental and neurological health. That’s despite a recent prospective study of nearly 1,000 older adults which found that a plant-based diet was able to slow cognitive decline in five separate areas.
The take-home message: The evidence is mixed. Plant-based diets offer some health benefits, but our understanding of exactly what they are and how this works is not completely clear. There’s no disputing that Americans love their meat-based dishes; just think of McDonald’s hamburgers, bacon for breakfast, and Thanksgiving turkey. That’s why nutritionists and public health officials have been making the case that eating meat is not an all-or-nothing proposition. There is clear evidence that simply eating less meat also offers some health benefits. And there are plenty of ways to do this. Campaigns like Meatless Monday encourage people to eat less meat without forgoing the hot dog at the ballpark or the Fourth of July barbeque.
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