Published in Nature Communications, Dr Alistair Senior, PhD candidate Caitlin Andrews and their team in the Charles Perkins Centre studied food supply and demographic data between 1961-2018 from 101 countries, with the data corrected to account for population size and wealth, to understand whether the type of protein a population consumed had an impact on longevity.

First author Caitlin Andrews said: “Our study suggests a mixed picture when it comes to comparing the health impacts of meat- versus plant-based protein at a population level.

“For the under-fives, a food system that supplies large amounts of animal-based proteins and fats — such as meat, eggs and dairy — lowered rates of infant mortality. However, for adults, the reverse was true, where plant-based proteins increased overall life expectancy.”

Methodology

To understand the impact of plant- and animal-based protein diets on human longevity, the researchers analysed publicly available data about the food supply of 101 countries across a 60-year period. The data included the amount of food produced per country, along with the levels of calories, proteins and fats available for consumption.

The countries studied represented a range of food systems, including countries where the consumption of animal-based protein is higher, such as Australia, the US, Sweden and Argentina, and areas where the consumption of plant-based foods is more prevalent such as Pakistan and Indonesia.

In order to compare the impact of different countries’ food supplies on life expectancy, the researchers corrected the data to take into account the differences in wealth and population size between countries. Having done this, they found that countries where overall availability of plant-based proteins were higher, such as India, had relatively longer life expectancies than countries where animal-based proteins was more readily available, such as the US.

Animal-based proteins and health conditions

Eating high levels of animal-based protein, particularly processed meat, has long been linked to a range of chronic conditions such as cardiovascular disease, type 2 diabetes and certain types of cancer.

Meanwhile, plant proteins — including legumes, nuts and whole grains — are associated with a lower risk or chronic diseases and overall mortality rates, with studies suggesting that plant-based diets have contributed to the longevity in the most long-lived communities on the planet — Okinawa in Japan, Ikaria in Greece and Loma Linda in California.

Lead investigator Dr Senior said: “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.

“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.”