Protein is having a moment, with supermarket and health store shelves groaning under the weight of shakes and bars. It’s estimated that around one in ten people in the UK eats a protein bar once a week – while a similar number regularly consumes protein powders.

And cost doesn’t seem to be an impediment. Look at the protein shakes sold at Joe and the Juice, the coffee and juice bar chain. It reported a record £45 million in profits last year, helped by the introduction of protein shakes.

Its latest Beets and Berries protein shake (which contains strawberries, beetroot powder, banana, date puree, collagen, whey protein and ‘sproud m*lk’ (a milk alternative made with pea protein and rapeseed and oat oils) costs £9, for instance.

Protein is vital for energy, growth, tissue repair and maintenance of our bodies, especially bones and muscles.

It supports the function of organs such as the brain, heart and liver. It also plays a vital role in maintaining aspects of normal body function: for instance, our antibodies, an essential part of the immune system, and haemoglobin, which carries blood around the body, are both proteins. Too little protein could affect your immunity and how fast or well wounds heal.

So should we all be buying – quite literally – into the trend for protein shakes and bars to boost our intake?

The risks (which include kidney stones and tooth decay) can outweigh the benefits if you overdo it.

The average adult is already having more than the recommended levels of protein (45g a day for women, 55g for men) – women are eating 67g per day and men, 85g, according to the Government’s National Diet and Nutrition survey.

And it is not hard to see why.

For a woman, for example, to eat the recommended amount of protein in a day she could have one egg for breakfast (6g); 6oz plain Greek yoghurt at lunchtime (18g); snack on a handful of nuts (4g); and 2oz of cooked chicken for supper (14g) and a milky coffee (3g).

The requirements of athletes and regular gym-goers may be slightly higher, as your body needs protein to repair and grow muscle that is broken down during exercise.

‘It’s around 1.2g to 2g extra per kilogram of body weight per day for endurance training and preserving muscle mass – and around 1.6g to 2.8g extra per kilogram of body weight per day during strength-gaining periods,’ says Dr Nicolas Berger, a senior lecturer in sport and exercise science at Teesside University. So if you weigh 60kg (9st 4lbs), you would need around 100g more protein for strength-building.

And it’s not just regular exercise that means your protein requirement increases, just getting older means you need more to maintain muscle strength.

Older people need around 1.2g to 1.5g extra protein per kg of body weight per day, according to a 2020 study by the University of Sheffield. They should consume 25-30g of protein at each of their three daily meals.

The requirements of athletes and regular gym-goers may be slightly higher, as your body needs protein to repair and grow muscle that is broken down during exercise

This is to prevent muscle wastage, which in turn can help prevent falls and general frailty, as well as certain illnesses such as pressure ulcers, and to speed up recovery from surgery – too little protein can affect wound healing and your ability to fight infection.

The optimum way to have protein, say experts, is from whole food sources, partly because many protein-rich foods are important sources of other nutrients, too.

‘It’s generally better to obtain protein from natural sources such as beans, pulses, soya, nuts, fish, eggs, and meat,’ says Lucy Jones, a dietitian and chief clinical officer of NHS weight management provider, Oviva.

‘These foods provide protein and other essential nutrients, including fibre, vitamins, minerals and beneficial fats.

‘Opting for whole foods for protein intake ensures a more balanced intake of all nutrients, which is often missed when using protein supplements.’

However, another concern regarding protein bars and shakes is their added ingredients, such as sweeteners and sugars.

‘Protein bars and drinks claim to provide a convenient way to increase or maintain protein intake, aid muscle recovery, support weight loss or muscle gain – and even claim to be complete meal replacements,’ says Dr Berger.

‘But this isn’t always true and often they have very little quality protein [i.e. a type that doesn’t provide all nine essential amino acids needed for muscle production or is in a form that can’t easily be used by our cells] – as well as lots of other poor-quality added ingredients.’

Common additives of concern, he says, include artificial sweeteners such as sorbitol and mannitol which can cause bloating and digestive discomfort.

‘The common thickener carrageenan is linked to inflammation, while the stabilisers guar gum and xanthan gum can cause digestive discomfort in sensitive individuals,’ he adds.

‘Such ingredients also make these options ultra-processed foods (UPFs) – foods that have been linked to weight gain, and increasingly conditions such as type 2 diabetes.

‘As such this could overshadow any health benefits.’

Dr Nicolas Berger, a senior lecturer in sport and exercise science at Teesside University

And then there’s the sugar. ‘A lot of protein bars have added sugar to improve their taste,’ says Raggi Munjal, a dentist based in South Yorkshire.

‘So if you have these bars regularly – one a day, for example – they can cause tooth decay like any chocolate bar would, because of the sugar attack on teeth.’

They’re also often high in calories for what is essentially a snack rather than a proper meal, which may increase unhealthy weight gain. (The Joe and the Juice Beets and Berries protein shake contains 371 calories, for instance.)

‘And the irony is that it’s not necessary to have excess protein – even if you are sporty,’ adds Jon Dearing, a consultant orthopaedic surgeon at Carrick Glen Hospital in Ayr, who specialises in sports injuries.

‘Excess protein will just be removed without being broken down or used by our cells.’

However, having too much protein can overwhelm this process. As Bhaskar Somani, a professor of urology at University Hospital Southampton, explains, it can hinder the function of the kidneys, and lead to kidney stones: pebble-like pieces of minerals. This happens when there is too much waste in the body and too little liquid to flush it out, which then can combine with the calcium in urine to form stones.

‘The stones can block the ureters – the tubes from the kidneys to the bladder – leading to infection and if left untreated and unrecognised even cause the loss of kidney function and even kidney failure,’ says Professor Somani.

‘I have had quite a few young patients coming to me with kidney stones with no previous history. And when I ask about their lifestyle, I discover they are having protein shakes. The quickest I have seen a patient develop a stone after starting with them is six weeks!’

Meanwhile earlier this year, researchers at the University of Pittsburgh found that consuming over a fifth of calories from protein can activate a type of white blood cell which can in turn clog up the arteries with plaque – a substance that damages the vessels, disrupting blood flow.

Poor blood flow is linked to a higher risk of stroke and heart attacks.

So does anyone really need protein shakes?

Dr Tom Crisp, a consultant in sport and exercise medicine at Queen Mary University of London, is unequivocal. ‘The hype surrounding protein shakes and bars is the biggest con.

‘Our daily requirement amounts to about one 8oz steak. Anything more than that is just an expensive way to make you pee more often.’

That’s because excess protein is excreted from the body in urine, making us go to the loo more.

‘If you are doing, say, competitive weightlifting you may need a bit more – but not a lot,’ he adds. 

Dietitian Helen Bond, a spokesman for the British Dietetic Association, agrees.

‘Most people have enough protein in their diet – it’s a myth that we need excess amounts. It’s just band-wagoning. Yet we are being sold the idea that we should pay a premium for it.’

Joe and the Juice did not respond to a request for a comment.