The truth about protein: how to get enough – at every age

<span>‘There is a sweet spot for protein.’</span><span>Composite: Guardian Design/Getty images</span>
‘There is a sweet spot for protein.’Composite: Guardian Design/Getty images

Eating protein is non-negotiable. Like carbs and fats, it’s a macronutrient that bodies need in relatively large, regular doses (compared with micronutrients such as vitamins and minerals). But our protein needs change throughout life, according to age, sex, activity levels and more. In fact our requirements can be highly individual and hence easily misjudged, especially when, says the dietitian Linia Patel, “There are conflicting messages around how much protein we should be eating.” On the one hand, the National Diet and Nutrition Survey shows that we exceed our daily protein recommendations, which scientists say could shorten our lives. On the other hand, says Patel: “What I see in my own clinical practice is that around 80% of my clients are not eating quite enough.” The booming protein industry, with its bars, pouches and shakes, would have us believe the more is always the merrier. So how much protein should we be eating?

What’s the official advice?

The recommended daily intake of protein for healthy adults is 0.75g per kilogram of body weight (or 0.8g if you’re in the US). This means, according to the British Nutrition Foundation, the average woman should eat about 45g of protein a day, while the average man should stick to around 56g – about two portions of nuts, tofu, fish or other protein source. Your ideal protein portion should fit into the palm of your hand. There are plenty of non-animal foods that are high in protein and rich in other nutrients and fibre to boot: beans, peas and lentils, soy products such as tofu, not to mention a plethora of nuts and seeds. You can find out how much protein is in individual foods by checking the packaging or consulting a website such as the British Nutrition Foundation’s. Some maths may be involved.

In the UK, the average daily intake is 76g a day for adults aged 19 to 64, and sits above the recommended levels in all age groups. However, these guidelines, says Patel, are under review, and “we clinicians have been trying to encourage the government to change the way they’re measured”. For a start, bodies skew heavier since these recommended averages were established. Based on today’s body weights, you’d be looking at a good 5g more.

Also, these suggested intakes were determined using “nitrogen-balanced” studies, which represent, says Patel, “the minimum protein we need to prevent malnutrition”. But preventing malnutrition, she argues, “is a whole different ballgame from thrive mode”.

A new technique for establishing protein needs has been developed, catchily called the indicator amino acid oxidation method. “It suggests the minimum protein intake for thrive mode, not just to prevent malnutrition, is about 1g to 1.2g per kilogram of body weight per day.” By this metric, national protein consumption levels don’t look as problematic. “As a woman in my 40s,” says Patel, “as my hormones decrease I will lose muscle mass. The 1g of protein will help me prevent that, not the 0.75g.”

The newer method is not a licence for people to overconsume protein, however.

What if you eat too much?

“There is undoubtedly a sweet spot for protein,” says Giles Yeo, a professor of molecular neuroendocrinology at Cambridge University and the honorary president of the British Dietetic Association. “And the big reason is that we cannot store it.” So any protein that’s not needed to build or repair tissue will be converted into fat, leaving nitrogen as a byproduct to be peed out. “That process , if taken to extreme, puts stress on our kidneys.”

Also, most of our protein consumption still comes from animal products, which often deliver more saturated fat than vegan sources, and meat elevates numerous cancer risks.

What if you don’t get enough?

Everyone knows protein is essential for replenishing and building muscle, but that’s not the half of it. “It’s needed to produce and transport hormones around the body,” says Patel, “and it’s important to make sure you have enough of the right building blocks for hormones, particularly as you get older, and production slows.”

Protein also affects mood regulation. Different types contain various amino acids, of which there are about 20 found in the human body, and some are, says Patel, “the building blocks for neurotransmitters, the chemical messengers that help govern your mood and memory”.

Protein helps appetite and blood-sugar regulation, too. “It’s a very complex molecule,” says Patel, “but on a basic level, your body has to work quite hard to break down amino acids, so if you include protein at a meal, it slows down the absorption of carbohydrate eaten with it, releasing it more slowly into your body.” Eggs on toast will fill you up for longer than jam on toast.

Part of the problem with ultra-processed foods, says Yeo, is that they tend to contain less protein, “and if you don’t have enough protein, but have access to other food, you end up eating more food”. This is the Australian obesity expert Prof Steve Simpson’s “protein leverage hypothesis”. “His argument,” says Yeo, “is that the lower protein content of some of the foods that we’re exposed to is one of the drivers of the continued obesity problem.”

And there’s more, Patel says: “Fifty per cent of your bone structure is protein. So a low-protein diet weakens your bones. And then, of course, because I’m vain, I want my skin and my nails and my hair to look great. One of the first signs when you’re a bit low on protein is that your nails become brittle. Your skin begins to suffer.” Because what do our bodies use to make collagen? It’s amino acids, silly.

What if you’re a child?

Patel and Yeo agree that if you’re able to give your children a balanced diet, you don’t need to be pedantic about protein levels. “Growing children can probably stand to take a little bit more protein because they’re using it,” says Yeo, but they’re smaller than adults, so their portions should still reflect that. The aforementioned official guide was made in 1991 when average body weights were lighter, but they start with 14.5g (about two big eggs) a day for one- to three-year-olds, 19.7g (add a small portion of peas) for four to six, 28.3g (one cup of cooked soya beans) up to 10, then the low 40s until 14. Then the sexes split and from 15, girls need a little more than the adult women’s figure, at 45.4g, whereas for boys the recommendation sits just below grownups at 55.2g.

How do you know if you’re getting enough?

As someone who works with everyone from endurance athletes to menopausal women, Patel knows first-hand that protein needs depend on factors such as age and activity levels. “It’s such an individual thing,” she says. “I might also need a little bit more than you, genetically.” You could work with a dietitian to establish your sweet spot, or try to learn for yourself. She generally advises adults to start by aiming to consume 1g per kg of body weight a day, and start monitoring muscle mass. The gold standard method is a Dexa scan, which uses low-dose X-rays, but most of us wouldn’t have access to one. The next best thing, she says, are the body composition scales you find at the gym. “They’re not accurate like a Dexa, but they can give you an indication over time, if they’re used right, like you’re weighing yourself at the same time every day and not after a workout.”

What if you work out a lot?

Even if you’re fit, it’s not about overdoing it and “eating a whole chicken a day”, says Patel. For bulky rugby players, the protein recommendation is “about 2g per kg in body weight per day, and they’re at the top of what the American College of Sports Medicine recommends.” So would regular people training for a 10k run or marathon, or simply working out regularly, need to take on more protein, or does that apply only to elite athletes? “Not at all,” says Patel. “You have that range from one to two grams and I would say one is where you start. For most gym-goers, and I would say for people who are running a little bit, it’s 1.2g, but it depends on your age.” And then as you’re more active, you move up that gradient, but make sure you boost your protein intake around activity. “There’s no point eating Nando’s chicken at dinner if you did a run in the morning, and you didn’t eat some protein in your breakfast.”

What if you’re pregnant?

Again, we’re all individuals, but Patel says that protein needs while growing babies “are not excessive. In general, you shouldn’t eat for two – you should just eat your healthy balanced diet. Only in the third trimester do you increase your calories by 300.” And when you do so, there’s no need to make a concerted effort to eat a higher proportion of protein, as long as you’re sticking to that healthy, balanced diet.

What happens when you’re middle-aged?

This is the ideal time for healthy ageing preparation, when hormone production starts dipping – oestrogen and progesterone in women and testosterone in men – and when sarcopenia (reduction in muscle mass) strikes. “We need to make sure we’re getting enough protein from middle age,” says Patel, “perhaps more markedly for women.” The official guide backs this up by upping a woman’s recommended average daily intake to 46.5g of protein. This is the time when we need to up the strength exercises to retain that muscle mass, too.

Do you need more or less in old age?

Valter Longo is a professor of gerontology and biological science at the University of Southern California, and an expert in the epidemiological longevity data that supports not exceeding the official protein guidelines. But even he says that from our late 70s we need a protein boost up to about 1g per kg of bodyweight, daily.

Using Patel’s preferred metrics, you’d already be consuming that, so it would be a little more. “As you age,” says Patel, “you become less efficient in using protein than when you were younger. And this is why elderly people need a little bit more to slow the natural reduction in muscle mass. An older person who’s trying to be active might need 1.4g per kg.”

The best way to consume it all, says Patel, is to spread your intake across your day, with each meal and snack including some protein. Roughly 20g of protein looks like “two eggs with two slices of seeded toast, or two slices of wholemeal toast with a tablespoon of peanut butter and a latte, or 125g of Greek yoghurt with some pumpkin seeds sprinkled on top”. If cottage cheese is your thing, a cup of that with an apple is a 20g protein snack, and meal-component wise, so is “a small chicken breast or half a big one, 75g of smoked or poached salmon or a cup of cooked lentils”.

In her view, eating enough protein is key to maintaining quality of life into old age. “If there’s one functional determinator of how well you live, it’s how much muscle you have,” she says. “That will determine whether or not you can get up the stairs or stand up from the sofa. Age-related muscle loss can have a serious impact on metabolic health and mobility.”

Should you vary your protein sources?

Without getting too technical about it, different protein sources offer different amino acids, and we need the whole gamut to keep ticking over nicely. So protein doesn’t always mean steak or hummus or whatever your favourite is – you need to eat a wide range. “My overall recommendations would be to include some protein at every meal and diversify your sources,” says Patel. This is partly why she doesn’t recommend protein shakes and the like. “Some protein shakes work for some people, as long as they don’t become a substitute for good, proper nutritional habits,” says Patel. “Because in a chicken, you’re not just getting protein, you’re getting magnesium, B vitamins, zinc and iron. In a protein shake, you’re just getting protein.”

• This article was amended on 15 April 2024. An earlier version said the British Nutrition Foundation recommends that men and women eat no more than 56g or 45g of protein a day, respectively. These amounts are guidelines, and not upper recommended limits.