More Plants, Less Meat Key to Longer Lives, Show Major Harvard & Sydney U. Studies

Yet more evidence has emerged that diets rich in plant-based whole foods and low in meat are the key to longevity.

Plant-rich diets will help you age better and live longer, according to two major studies that spotlight the ill health effects of animal proteins.

Researchers at Harvard University and the University of Sydney studied large-scale consumption patterns to determine the most health-promoting diet and found that whole-food plant-based eating is the key to lowering mortality rates.

The findings come at a time when meat and dairy are regaining popularity in countries like the US and the UK, driven by advocates of raw milk and the carnivore diet, rising concerns around ultra-processed foods (UPFs), and political support for animal proteins.

Some of the criticism is tied to vegan meat alternatives, whose volume sales in the US dropped by 2.3% in 2024, against a 4% increase for conventional meat. Experts argue that these products don’t reflect the entire plant-based diet.

Miyoko Schinner, founder of vegan cheese pioneer Miyoko’s Creamery and a University of California professor, noted we “can’t conflate products with the future” of the plant-based sector. “We’re just focused on the sales of products that we’re making, and that doesn’t reflect the entire picture,” she told Green Queen in January.

“The whole world’s not going to go vegan because there’s Beyond Burger, right? But they might go vegan if we promote a plant-rich diet,” she said. And these two studies argue that doing so might help you live better too.

Harvard study: plant-rich diets will help you age better

At the Harvard TH Chan School of Public Health, researchers investigated the midlife diets and eventual health outcomes of more than 105,000 Americans over a 30-year period, noting that diet is the second-largest behavioural risk factor for mortality in the US (after tobacco).

They scored participants based on how well they followed eight dietary patterns that promote healthy ageing – each emphasises a high consumption of fruits and vegetables, whole grains, unsaturated fats, nuts, and legumes, and low to moderate intake of fish and certain dairy products. They also looked at the consumption of UPFs.

Nearly a tenth of the participants aged healthfully, with adherence to one of the eight dietary patterns linked to better cognitive, physical, and mental health. On the flip side, higher intakes of processed meat as well as sugary and diet beverages were linked to lower chances of healthy ageing.

The leading diet was based on the Alternative Healthy Eating Index, which was developed to prevent chronic diseases and is rich in plant-based whole foods and low in red and processed meats, sugary drinks, sodium, and refined grains. Participants who stuck to this diet were 86% more likely to age healthily at 70 years, and over twice as likely at 75.

Another leading diet was based on the Planetary Health Diet Index, which emphasises plant-based foods and minimising animal proteins to improve both human and planetary health.

“Our findings suggest that dietary patterns rich in plant-based foods, with moderate inclusion of healthy animal-based foods, may promote overall healthy ageing and help shape future dietary guidelines,” said co-corresponding author Marta Guasch-Ferré.

It’s a highly relevant point, since scientists have recommended that the US Department of Agriculture prioritise plant proteins and encourage Americans to cut back on red meat in the upcoming dietary guidelines.

The research, published in the Nature Medicine journal, follows a December 2024 study by the Harvard Health School, which found that a higher ratio of plant proteins to animal-based foods can improve heart health. And in March, its researchers were part of another analysis that suggested replacing less than a tablespoon of butter with plant-based oils can lower the risk of premature death from cancer and other causes by 17%.

Populations with high plant protein intake have longer lives

Across the Pacific, experts at the University of Sydney’s Charles Perkins Centre assessed demographic and food supply data from 101 countries over almost 60 years. This included regions where meat consumption is high, like the US, Australia, Sweden and Argentina, as well as places such as Pakistan and Indonesia, where plant-based food intake is more prevalent.

Since it’s hard to compare the countries very easily, the researchers corrected the data to account for income and population size. Doing so revealed that nations with higher availability of plant proteins had longer life expectancies than those where animal proteins were more readily available.

For children under five, easy access to higher amounts of meat, dairy and eggs was linked to lower mortality, with the researchers noting that adding energy from any protein source – plants or otherwise – was beneficial for kids. They stressed that the findings “do not refute the advantage of incorporating plant-based proteins in a malnourished environment”.

In adults, however, plant proteins increased overall life expectancy. “The optimal balance of protein and fat in national food supplies – which correlates with minimal mortality – varies with age, suggesting that reductions in dietary protein, especially from animal sources, may need to be managed with age-specific redistributions to balance health and environmental benefits,” the authors wrote in the Nature Communications journal.

“Protein is a crucial part of the human diet, but as eating habits change and developed countries look to decarbonise, where we get our protein from has come under greater scrutiny,” said senior author Alistair Senior.

“The knowledge that plant-based protein is associated with a longer life is really important as we consider not only how our diets impact our own longevity, but the health of the planet.”