Meat or plant protein? Age matters

Think of a dinner table. On one side, you’ve got sizzling steaks, grilled chicken, and cheese. On the other, steaming bowls of lentils, roasted chickpeas, and nutty whole grains. The global conversation about food and health often pits these two camps, animal-based proteins and plant-based proteins, against each other. But what if the right answer isn’t about picking a side at all, but about timing?

A study published in Nature Communications from researchers at the University of Sydney suggests just that. The team, consisting of scientists Caitlin Andrews, David Raubenheimer, Stephen Simpson, and Alistair Senior, analyzed decades of global data to explore how different kinds of proteins in national food supplies relate to survival at different stages of life. Their findings? The “best” protein source might depend not only on what you eat, but when in your life you eat it.

Indeed, our food choices shape more than waistlines: they shape the planet. Food systems account for about one-third of all greenhouse gas emissions, and scientists worldwide have argued that shifting away from meat and toward plants is essential for sustainability. However, animal and plant proteins aren’t identical. They differ in amino acid composition, digestibility, and micronutrients like iron and vitamin B12. So, while replacing animal protein with plants may help the planet, what does it mean for human health, especially across the lifespan?

That’s the puzzle Andrews and her colleagues set out to solve. To this end, the team pulled together a massive dataset consisting of food supply records from the UN’s Food and Agriculture Organization (covering 101 countries, 1961–2018), mortality and survival data from the Human Mortality Database, and Economic data from the Maddison Project Database.

In other words, they weren’t looking at individual diets, but at national food availability: what was in the supply chain, on average, for people to eat. While this isn’t the same as what individuals actually consumed, it captures the broader nutritional environment in which a country’s citizens lived.

The study zeroed in on two crucial survival markers: survival to age 5 (early-life survival) and survival to age 60 (later-life survival). Here’s what they found. Animal protein helps early in life. In environments where fat and calories were sufficient, countries with more animal-based protein in their food supplies had better early-life survival. This makes sense biologically: animal foods are rich in easily absorbed amino acids and critical nutrients like iron, zinc, and vitamin A, all essential for growth and development. For infants and young children, these nutrients can be life-saving. They also found that plant protein helps later in life. In contrast to their first finding, for people living into middle and older age, countries with more plant-based protein in their food supply had lower mortality rates. High plant protein availability correlated with longer life expectancy and reduced risks of chronic diseases like heart disease, diabetes, and some cancers. Finally, fat is a double-edged sword. Higher fat in the food supply supported survival in early life, but in later life, it correlated with worse outcomes. Too much fat, especially when combined with high meat consumption, appeared linked to shorter lifespans.

In short: animal protein supports survival early in life, plant protein supports survival later in life.

But why would this be?

Think of animal protein as rocket fuel: powerful, nutrient-dense, and great for rapid growth, but over the long haul, it might damage the engine. Processed and red meats, for example, are linked to cardiovascular disease and cancer. Plant protein, meanwhile, is more like a steady battery: slower, gentler, and protective over time. Legumes, nuts, and whole grains don’t just deliver protein; they also bring fiber, antioxidants, and other compounds that reduce inflammation and support long-term health.

The researchers even showed that in “isocaloric swaps” (replacing animal protein with the same calories of plant protein), later-life survival consistently improved.

If this sounds familiar, it’s because some of the longest-lived populations on Earth, the so-called “Blue Zones” like Okinawa in Japan and Ikaria in Greece, have diets dominated by plants, with only small amounts of animal protein. These communities tend to avoid processed meats and instead focus on beans, vegetables, and whole grains. The Sydney team’s findings fit perfectly into this picture, but add an important nuance: "early in life, animal foods may still play a critical role, particularly in regions where malnutrition is common."

The findings are deeply relevant for global policy: once again, nutrition and sustainability policies must be tailored, not one-size-fits-all. Also, the research aligns with a growing body of evidence suggesting that children and young people need sufficient protein, and animal sources can be especially important where malnutrition is a risk, whereas adults in mid to late life benefit from diets richer in plant proteins, with less reliance on red and processed meats.

If you want to learn more, the original article titled "Associations between national plant-based vs animal-based protein supplies and age-specific mortality in human populations" on Nature Communications at https://doi.org/10.1038/s41467-025-58475-1.