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