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How much protein do we need for optimal health? According to a growing body of evidence, more than has been recommended in the past.
What is protein?
Protein is one of the building blocks of our bodies; one of the three main macronutrients - along with fat and carbohydrate. When you hear people talk about 'counting macros' - protein is one of those. Protein is made up of smaller molecules called amino acids. Our bodies can produce some amino acids, and others we need to get from the protein foods we eat.
Protein is also an enduring global trend in food. 'High protein' has become a common claim on the packaging of foods from every aisle in the supermarket, from bread to yoghurt.
And while there’s a fair few health claims that are more marketing than science, there’s some solid evidence - with more emerging - behind why many of us might benefit from foods with a protein boost.
What does protein do?
One of protein's main roles in the body is growth and repair. It helps in the formation of muscles, hair, nails, skin and organs. If the body is under extra demand - if you're an athlete; a growing teenager; pregnant or breastfeeding or you are sick or injured - you might well need more protein to keep that growth and repair going.
If we don't eat enough protein, we might have lower immunity; mood and concentration issues; feel weak or hungry, and we could lose muscle mass, especially as we get older (see below).
Protein also gives us a feeling of satiety: we feel full and satisfied when we eat it. There is a theory known as protein leverage that we are wired to seek out a certain amount of protein from our food, and we will keep eating until we hit that point, no matter the calories. Foods higher in protein play an important role in regulating our appetite.
Why do we need it?
As we age - from our 30s onward, in fact - we start to gradually lose our muscle mass. This is accelerated in women at perimenopause and beyond, but it's also a natural part of ageing for all genders.
We need to keep our protein intake up to help us maintain that muscle, which protects our bones, too. As we get older we become a bit less efficient at using the protein we're eating, so we might need to consume a bit more to give ourselves the best chance of making the most of it.
Holding on to our muscle is important because there's evidence to show it'll help with long-term health and can even impact longevity. Lower muscle mass is associated with higher rates of metabolic syndrome and heart disease, and having more muscle is associated with a lower risk of death from any cause. Being strong and able to move well also means we can stay active and independent as we get older.
Exercise physiologist and nutrition scientist Dr Stacy Sims is an advocate for prioritising protein. She says it's key, especially for women and for all of us as we age.
"That's with the aim really of maintaining and building muscle mass, even if we're not consciously in the gym trying to do it.
"When we have regular doses of protein, then we're going to keep what [muscle] we have, so then when we're 80 and we're walking along and we fall, we don't necessarily break our hip."
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How much protein is enough?
That depends on your age, gender and activity levels. There are official guidelines for protein in New Zealand that set recommended daily intakes. These are in line with those in other countries.
However, there's a growing school of thought among nutritionists that these are set far too low for optimal health. Sims is among those; she says the RDIs are woefully low, especially for women.
"The [official] reference range for women came from sedentary old men", she points out - the thinking being that older men and younger women have about the same amount of muscle mass.
"But the muscle quality is different," Sims says.
Women, she says, need far more than the 0.75g - 0.94g of protein per kilo of body weight officially recommended. She suggests protein levels of between 1.6g and 2.2g of protein per kilo; the amount goes up as we get older and through to post menopause. For a 65kg woman, that would be between 104 and 143 grams of protein a day.
For men, official recommendations are for between 0.84g and 1.07g per kilo - again, increasing as we get older - but here again, nutrition experts often recommend higher levels. Around 1.6g per kilo seems to be a good level to aim for, with more if you're doing a lot of exercise.
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How do I get enough protein?
Those recommendations might seem high, but Sims reckons it's possible to get enough protein from our food if we're focusing on spreading it out throughout the day. And we don't need to be weighing and measuring every morsel, either.
"We want to have a fist-sized portion of a protein food at every meal," Sims says. That amount supplies between 25 and 30 grams of protein.
"It doesn't have to be meat", she stresses.
"It can be eggs and dairy and nuts and seeds, a whole conglomerate of things that will give you this much. So if you get that at every meal, and then at every snack you're having some kind of protein, you should be readily able to get up to about that 110 gram mark."
Supplementing with protein powder on days when you're doing heavier muscle-building exercise, Sims suggests, will easily get you up to an even higher dose. And she says we shouldn't only focus on meaty sources.
"Porridge with nuts - that has protein. If you're doing porridge with nuts and yoghurt, then you're getting a good 20 or more gram hit. We should think beyond the traditional proteins."
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Can you have too much protein?
It has been believed that eating high levels of protein could put pressure on the kidneys and cause problems. However the body of evidence now shows that in healthy people, there's no risk of this happening. If you have existing kidney issues or kidney disease, though, it's a different story: your protein intake needs to be carefully monitored, so take your advice from your medical professional.
