Strength training is now the go-to for healthy ageing, with benefits newly revealed for the body and brain in preventing illness and injury. In Part II of the Listener’s feature on the new science behind strength training, how much protein is enough? You can read Part I here.
We need to eat protein to build and keep muscle, especially if we’re strength training. It’s an essential building block of the body.
Protein is now a big and persistent trend. Eat more protein, we’re urged by social media and marketing alike. Protein influencers have sent sales of cottage cheese – formerly an overlooked and old-fashioned dairy item – spiking upwards, and recommendations for supplements are everywhere.
But how much protein do we really need? The recommended daily intake for adult men in New Zealand is 0.84g to 1.07g per kilo of body weight, increasing with age. For women, it’s 0.75g to 0.94g. Those numbers are in line with other countries but now it’s widely acknowledged that it’s not enough for optimal health.
“We all agree that’s too low,” says physiology researcher Lauren Colenso-Semple, who explains if people are eating protein at those levels, it’s worth trying to get more. “If you bump it up to about 1.2g per kilogramme, there is a real benefit.”
For a 90kg man, that’s 108g of protein a day; for a 70kg woman it’s 84g. Fitness experts and influencers often promote levels far higher than this, but Colenso-Semple says it’s not a one-size-fits-all situation, according to evidence.
“It’s conceivable if you’re trying to really maximise your muscle growth, that going to 1.4 or 1.6g per kilo might be reasonable. After that, we start to see diminishing returns. Once we start getting higher than 1.6g, we’re not really seeing much benefit, at least from a muscle level.”
For most people, “enough protein” will look like a high-quality protein source with every meal. That can be from animal foods – meat, eggs and dairy – and from plant sources such legumes, grains and pulses. It all adds up.
If hitting that target is a struggle, adding in a protein shake – which typically contains around 25g of protein – might help, Colenso-Semple suggests. This can be particularly useful for older people whose appetites have waned.
Going higher on the protein isn’t harmful, but on its own won’t necessarily prevent a slide into sarcopenia. It’s more important to do the strength work. “The stimulus for muscle growth is lifting weights.”
Listener nutrition columnist Jennifer Bowden backs up comments that a high-protein diet is not harmful, at least in the short term, and points to guidance from the International Society of Sports Nutrition (ISSN). It recommends higher protein intakes of 1.4 to 2g per kilo of bodyweight per day for those who exercise regularly. The ISSN notes no evidence of harm in healthy, active individuals consuming up to 3g per kilo.
However, Bowden points out much of this evidence comes from short-term studies, and the long-term effects of very high-protein diets remain unclear; therefore, a balanced approach is wise.
Bowden also cautions individuals with existing kidney disease to be mindful of high-protein intakes.
She adds increasing protein should not come at the expense of other foods such as fruits, vegetables and wholegrains.
Whole-food sources of protein are generally preferred to supplements such as protein powders, as they provide a broader range of nutrients such as fibre, vitamins, minerals and healthy fats.
