After years of being the also-ran, plant protein has taken its place alongside animal protein in many supermarket chillers. Beef sausages line up with plant versions made from legumes, not cows – and the choice of plant-based burgers, meat balls and schnitzels keeps on growing.
But how does protein from plants stack up against protein from animals?
“All animal foods, including eggs and dairy, contain all of the nine essential amino acids humans need to get from food, but most plant sources of protein like legumes, nuts and seeds lack one or more which means you need to eat them with another plant protein food such as a grain to get all nine essential amino acids,” says dietitian Dr Rosilene Ribeiro of the University of Sydney’s School of Life and Environmental Science.
“Beans and rice are a good example – beans are missing an amino acid called methionine, while rice lacks an amino acid called lysine but eaten together they supply all nine essential amino acids.”
This might sound complicated but combining foods like this comes naturally to people all over the planet: think dahl and rice, baked beans on toast, peanut butter sandwiches or bread and hummus.
“If you follow a vegan diet it’s good to get all your amino acids together in one meal but as long as you eat a variety of plant protein sources through the day you should get the right mix of amino acids,” Ribeiro says.
“The only plant foods containing all nine essential amino acids are quinoa, soy and amaranth seeds.”
Another difference is what the protein comes with, adds Melbourne-based dietitian Skye Swaney.
“With plant protein, we get other beneficial nutrients like fibre and polyphenols, while animal sources of protein like meat, fish and dairy can be rich in nutrients like easily absorbed iron, B12, calcium and omega 3 fatty acids.”
But most adults can meet their protein needs fairly easily on a plant-based diet, she adds – you just might need bigger helpings.
“Animal foods are typically higher in protein relative to their kilojoule content, so you may need a larger portion of a plant food to get the same amount of protein as you would from an animal source,” she explains.
“Children can get enough protein from a plant-based diet too, but it needs careful planning to ensure there’s sufficient iron, B12 and calcium as well – if your child’s diet is vegan or mostly plant-based it’s a good idea to consult an accredited practising dietitian to make sure their diet is on the right track.”
How much protein we eat matters too – and too much does us no favours, according to Ribeiro who says most people in Australia are meeting their protein needs – and many of us eat too much.
“Consuming a lot of protein forces your body to work faster to process it and the faster your body works, the more likely it is to make a mistake, raising the risk of diseases including cancer,” she says. “It’s also about what the protein comes with – if it comes with high levels of saturated fat, as in fatty cuts of meat, it can increase the risk of heart disease.
“This may explain why observational studies of long-lived people have linked traditional diets low in protein and high in carbohydrates to longer lifespans,” she says. “But we can reduce the amount of protein in our diet by replacing some animal sources with plant sources of protein because plant sources naturally contain less protein per gram. ”
Yet it’s also true that a higher protein intake benefits older people to help offset age-related muscle loss, adds Ribeiro whose research focuses on nutrition and longevity. The recommended protein intake for adults is around 0.8g per kilo of bodyweight and rises to 1g per kilo for over 70s.
“Some researchers suggest that for longevity we need low protein, high carbohydrate diets as younger adults – but switch to a higher protein intake as we get older. But we need more research to be sure. ”
Can plant protein do a decent job of building muscle for athletes?
“We’re seeing more athletes switch to a plant-based diet for different reasons, including health, sustainability and animal welfare,” says sports dietitian Bethanie Allanson of Sports Dietitians Australia. “I work with the West Australian Cricket Team, for example, and some of their players have changed to a plant-based diet. Research shows that for endurance and strength, including powerlifting, a well-managed plant-based diet doesn’t hinder performance, although it doesn’t enhance it.
“It just takes more effort to ensure you get all the essential amino acids and nutrients you need. Some athletes use protein supplements but it’s mainly for convenience when they’re travelling, for example.”
Still, when it comes to buying plant-based meats and products like plant-based burgers, check the label first, says Swaney.
“They’re often highly processed and high in sodium – if you want to include them, choose products that are lower in sodium and with a high content of whole foods like legumes, wholegrains, nuts and seeds.”