Protein is a building block for organs, tissues, muscles, bones and skin, but how high should our intake be?

We’re advised to consume foods rich in protein to keep us fuller for longer and build muscle. But how high should our intake be, and can we get too much of a good thing?

Protein is a building block for organs, tissues, muscles, bones and skin. In the absence of carbohydrates and fats in the diet, its calories can be used as energy. The question of how much we need is not as easy to answer.

A recent trip to the supermarket left me wondering if I were missing a nutritional trick. In the chilled cabinets were yogurts, puddings and shakes with the words ‘high protein’ emblazoned across them in attention-grabbing print. 

The cereal aisle had breakfast options proclaiming their protein content would power me through my day. Near the till were protein bars, bites and powders, including a strawberry-flavoured one for €80 a kilo.

Nóra Ní Fhlannagáin, a sports dietitian and lecturer at Atlantic Technological University in Galway, says whey is usually the ingredient that gives the products their high protein content.

“When cheese is made, the fat and casein proteins in the milk form curds, which become the cheese, and the leftover watery liquid is whey. It was once fed to pigs, but is now dried into powder that’s naturally high in protein. In plant-based products, the protein usually comes from dried peas or soy.”

Protein is a building block for organs, tissues, muscles, bones and skin. In the absence of carbohydrates and fats in the diet, its calories can be used as energy. The question of how much we need is not as easy to answer.

“The European Food Safety Authority advises 0.8g of protein per kilogram of bodyweight per day for adults,” Ní Fhlannagáin says. 

Nóra Ní Fhlannagáin: "If you’re an active person who exercises, particularly if you lift weights — as we should all be doing — you will benefit from up to 1.6g per kilogram.”

“But that’s to prevent deficiency. If you’re an active person who exercises, particularly if you lift weights — as we should all be doing — you will benefit from up to 1.6g per kilogram.”

The reason for this higher requirement is that exercise places stress on muscle fibres, causing microscopic damage. Ní Fhlannagáin says this “micro damage is normal and desirable because the muscle grows back bigger, better and more powerful”.

“It’s called training adaptation, and protein provides the amino acids required to repair, rebuild and make it happen.”

Older people also have higher protein needs because their ability to use protein diminishes with age.

“Our muscles become less efficient at taking up the amino acids in protein,” says dietitian Sharon Madigan, head of performance nutrition at the Sport Ireland Institute. “This can lead to a loss in muscle mass of 8% to 10% a year from our 30s unless we take steps to ensure sufficient protein intake.”

Food for thought

According to online chatter from Stanford University professor Andrew Huberman, who hosts a podcast, protein may also have cognitive benefits.

He’s particularly enthusiastic about creatine. “Creatine is made from amino acids found in protein-rich foods and has been taken by athletes for years to help with muscle building and recovery,” says Madigan.

“It allows them to repeat short bursts of high-intensity exercise such as sprinting or weightlifting so that they require a shorter pause for rest between repetitions. Many athletes take it daily.”

There was a time when creatine supplements were considered controversial, as they were believed to damage the kidneys and liver. But clinical trials disproved this in the early 2000s.

Sharon Mafigan: "Creatine is made from amino acids found in protein-rich foods and has been taken by athletes for years to help with muscle building and recovery."

Since then, there has been a boom in creatine products, and follow-up studies have shown that creatine may do more than enable people to lift heavier and push harder. It could ease symptoms in people with neurodegenerative diseases and stroke; improve memory, attention and information processing in adults; and even mitigate the effects of a bad night’s sleep. No wonder it’s proving popular with Huberman and other wellness and longevity gurus.

Madigan isn’t as convinced. She points out that most of the research has been conducted on people who are creatine-deficient.

“The jury is still out with respect to its cognitive effects on healthy young individuals,” she says.

“However, it may be beneficial to older adults, helping them maintain function and keep up the activities of daily life as they age.”

Ní Fhlannagáin warns of possible side-effects of taking creatine, including bloating, cramping, constipation, and dehydration. “It should only be taken in the correct dosage under the guidance of a sports nutritionist,” she says.

While some people double down on protein to bulk up, others fill up on it to slim down. The low-carb, high-protein Atkins diet first established the link between protein and weight loss in the 1970s.

“Our culture is obsessed with being thinner, and because protein is satiating and keeps us full for longer, it can help us go into a calorie deficit and lose weight,” Ní Fhlannagáin says. “That’s yet another reason why we see so many protein products for sale.”

More is not always more

If they can help us bulk up or slim down while also bestowing possible cognitive benefits, shouldn’t we all be eating these products? That’s perhaps what marketers would like us to think, but Madigan believes it’s too simplistic.

When it comes to weight control, she says, “the body needs to get energy from somewhere. Fat stores are the first route, but the second is protein stored in muscles, which can lead to muscle loss. So, while we can lose weight by cutting carbohydrates in favour of protein, we need to be mindful where that weight loss is coming from.”

When it comes to muscle building, Ní Fhlannagáin says more is not always more. “Some people think they will build more muscle by adding more protein to their diet. But there is a threshold, which hovers around 1.6g of protein per kilo of bodyweight, and once you reach it, more won’t make your muscles bigger. It’s also worth remembering that protein alone doesn’t grow muscles. It has to be accompanied by exercise.”

Problems can also result from prioritising protein over other nutrients. A lack of fibre can lead to constipation. Not enough fruit and vegetables can lead to vitamin and mineral deficiencies.

“Athletes also increase their risk of injury if they don’t have enough carbohydrates,” Ní Fhlannagáin says. “We mustn’t fall into the trap of eating so much protein that it pushes out other vital nutrients.”

The secret may lie in improving our diet, rather than reaching for supplements. “My advice to anyone concerned about their protein intake is to eat meat like chicken, beef, and lamb as well as oily and white fish,” says Ní Fhlannagáin. “Tuna probably packs the biggest protein punch per calorie of all foods. Dairy products like milk and yogurt are great as are eggs, soya products, beans, peas, nuts, and lentils.”

Madigan recommends eating as many forms of animal and plant proteins as possible. “Take porridge, for example,” she says. “It has some protein, and when you add milk, nuts, and seeds and maybe Greek yogurt, you have a breakfast that contains lots of different nutrients, including plenty of protein.”

Where protein powders can help is if you struggle to eat enough protein. “My father, who is 80, adds protein powder to his food,” says Ní Fhlannagáin. “His appetite isn’t what it used to be, and he can find it hard to eat enough protein to maintain his muscle mass.”

However, she doesn’t recommend protein bars, saying that “they may contain protein, but they are often ultra-processed and unhealthy”.

If you’re tempted to pick one up while shopping, Madigan urges you to check the ingredients list and choose the one with natural ingredients like nuts, fruits, oats, and seeds.

“The more ingredients there are, the more you should steer clear,” she says. “A lot have added polyols to make them sugar-free but these can cause bloating and gut issues and should be avoided.

“As someone smart once said: If your granny wouldn’t recognise the ingredient, don’t eat it.”