Once the preserve of bodybuilders, protein supplements are now being stirred into morning coffees, spooned into yoghurt, baked into flapjacks and marketed to everyone from busy professionals to menopausal women.

Sold as the perfect supplement for muscle power and growth, this year alone the global protein supplement market is estimated to be worth around £21billion – with powders accounting for more than half of sales.

Experts say that generally for athletes or older adults struggling to eat enough protein, powders can be a useful convenience.

But their popularity is much more widespread: in the UK, a quarter of adults regularly consume protein shakes, for instance. And among 25-to-34-year-olds, it’s higher – 37 per cent, according to research by YouGov. There is no question that protein itself is vital – along with fat and carbohydrates, it is one of the essential macronutrients we need to consume every day’, says Ro Huntriss, a dietitian based in London.

‘It helps to build and repair muscle, as well as hair, skin and nails – and supports your immune system.’

While dairy, meat, fish and eggs are the most regularly consumed protein sources, many are now turning to protein powders to meet their daily needs. But experts believe this trend has raced ahead of the science supporting its health benefits, as we reveal.

DO YOU ACTUALLY NEED THAT MUCH PROTEIN?

Government guidelines recommend 0.75g of protein per kilogram of body weight per day. This equates to 56g for a man weighing 75kg (11st 8lb) and 45g for a 60kg (9st 6lb) woman. However, the British Nutrition Foundation says most people already exceed this amount – with men averaging around 85g per day and women around 67g.

‘The guideline amounts are based on the amount needed to stop us losing muscle tissue and wasting away,’ says Stuart Gray, a professor of muscle and metabolic health at Glasgow University.

Protein, which many may take as part of a fitness routine, won’t necessarily help with your performance. Instead, its main role begins after you’ve finished training

‘Protein is important for development and growth, but at a population level [on average] in the UK, we get 1.1g to 1.2g per kilogram – which is plenty.’ But the type of protein is important, he adds.

As well as the obvious sources, such as chicken breasts and egg whites, you might not realise it’s also found in many everyday foods including bread, beans, oats, peanut butter and potatoes – all these sources add to our daily intake.

The problem is people are relying increasingly on ultra-processed, ‘high-protein’ products, such as bars, supplements and powders – and these have an undeserved health halo, says Professor Gray.

‘Often these “high protein” foods are essentially chocolate bars with a lot of sugar and fat – and some protein added. Everyone’s going for these foods, but really they don’t need to. When possible, a wholefood-first approach is better because you will get lots of other useful nutrients from it, too.’

This is important because protein, which many may take as part of a fitness routine, won’t necessarily help with your performance.

In a study last year, cyclists who were given a carbohydrate and protein powder did not perform any better than those taking a placebo. The 12 participants cycled for 100 minutes on a stationary bike, combining easy cycling with harder intervals. They also completed a 20-minute time trial going as hard as they could.

The research, published in the International Journal of Sport Nutrition and Exercise Metabolism, showed no difference in performance or perceived exertion between those given the supplement or the placebo.

‘Protein is mostly used for building muscle, so it is useful for athletes for recovery and repair post-exercise,’ says Professor Gray.

‘From an endurance point of view, it doesn’t contribute any energy to any useful degree and it won’t have any benefit.’

Instead, protein’s main role begins after you’ve finished training.

That’s because when you challenge a muscle with resistance – and this applies to endurance exercise, too, as muscles are continually put under strain – you’re putting it under tension that it’s not used to.

This forces your body to adapt, so it repairs and also reinforces your muscle fibres, making them stronger and more able to cope with that weight in the future.

This process depends on amino acids – the building blocks of protein – from dietary sources.

‘Within the muscle, we’ve constantly got a breakdown and build-up of muscle proteins,’ says Graeme Close, a professor of human physiology at Liverpool John Moores University.

‘So it’s important that we’re eating protein on a regular basis. And if you want to grow muscle, you need to consume more protein than you’re breaking down on a daily basis.’

TRUTH ABOUT 30G PROTEIN MEAL

There’s a long-held view that you must eat 30g of protein in every meal. In fact Professor Close says while you don’t need to be too strict with the amount per meal, what is important is spacing out your protein intake – i.e. don’t skip it all day and pack in as much as you can in the evening meal.

‘If your dinner is at 7pm, that’s a prolonged period of time and the body is constantly using the amino acids that it’s got circulating in the blood to rebuild.

‘With no amino acids coming in, it will use its own – and if that happens over time, muscle mass can gradually decline.’

One study, published in the Journal of Nutrition in 2014, found people who spread protein more evenly across the day experienced higher rates of muscle protein synthesis – the process of building muscle – than those eating most of it in one meal.

THE MYTH COSTING SHOPPERS BILLIONS

Protein, and protein powders specifically, are often branded as a shortcut to a leaner, fitter and stronger body. And some premium brands can cost upwards of £65 per kilo. But experts warn that not only do we probably not need as much protein as we think, but protein supplements are a waste of money without exercise.

‘My big gripe is that people think protein will rescue them from not doing exercise,’ says Professor Gray. ‘To grow muscle you need protein – but in the absence of exercise, added protein does nothing.’ The real driver of muscle growth is resistance training – challenging muscles with weights, resistance bands or even your own body weight.

‘If you’re doing resistance training, you’ll gain a small extra muscle-building benefit of taking protein,’ says Professor Gray.

Journalist and personal trainer Lucy Gornall learned that generally for athletes or older adults struggling to eat enough protein, powders can be a useful convenience. But their popularity is now much more widespread

‘The muscular system takes it up and utilises it – but only up to 1.6g of protein per kilo of body weight. After this, the benefits plateau.’

And if you’re not doing resistance training but still taking extra protein, the body doesn’t require it – so any surplus will either be excreted as waste or stored as fat.

Professor Gray adds: ‘Even with exercise, once you move beyond consuming 20g to 30g of protein in one go after exercise, a lot gets excreted. I see a lot of people take a 60g protein shake, but the body has a limited capacity.’

Studies show that in those under 65, the best muscle-building response is with protein intake of around the recommended 1.6g per kg of bodyweight per day. (A 60kg woman would aim for 96g of protein a day – the amount in 400g of chicken breast for instance). In those over 65, the sweet spot is around 1.2 to 1.59g per kg. Any more makes no difference.

DOES 30-MINUTE PROTEIN WINDOW REALLY HELP?

Many gym-goers follow a mantra that there’s a 30-minute window after exercise to consume protein if they want to maximise muscle growth.

Known as the ‘anabolic window’, the theory is that muscles can only make the most of protein during a brief period immediately after a workout.

But experts say this window is likely much wider than people think. ‘There’s evidence that the muscle remains sensitive to protein possibly up to 48 hours – so there’s no crazy rush to get protein in,’ says Professor Gray.

‘When you look at studies suggesting protein is most effective straight after exercise, a lot of them have been done in controlled lab conditions and people often come in having fasted.

‘They’ll exercise, take protein and they might see a small benefit when it’s taken sooner rather than later, although it’s not much.’

In the real world, he adds, ‘someone might eat before exercising and so probably has protein in circulation anyway – so it becomes even less important to rush to get protein in after’.

ARE YOU BUYING THE BEST STUFF?

If you struggle to hit your protein intake through food, or need a convenient way to hit your target on busy days, a protein powder can help. However, it’s worth knowing what to look for.

‘Protein powders are generally classed as ultra-processed foods (UPFs) but not all UPFs are nutritionally equivalent,’ says dietitian Ro Huntriss.

Traditionally, most powders were made from whey protein, derived from liquid left over during cheese-making. Today there are also plant-based options made from peas, soy, hemp and rice. ‘A whey protein powder primarily provides a high-quality protein source, whereas some may be high in sugar, salt and saturated fat with little nutritional value,’ says Ro Huntriss.

Professor Graeme Close, a specialist in human physiology, also warns that some supplements you buy online contain enough prohibited ingredients for an athlete to fail a drug test – due to traces of heavy metals, such as lead and cadmium.

‘Look for a company’s certification of its manufacturing practices and what is in the product.’ This will usually be on its website.

And his advice for women is to be wary of products marketed in pink packets and said to help ‘tone’ or ‘slim’ or work better for menopause.

‘Females don’t need a different type of protein to males, he says: ‘Protein intake is based on weight, not gender. So, if you weigh less than a male, you probably just need less.’

Here's what else you should eat to keep your muscles strong

By dietitian Dr Emily Leeming

Why do muscles matter? If you ever struggle to open a stiff jar or find it takes a little longer to get out of a chair, you might give it some thought, but muscle strength is not only important for going about your daily life, it can be an early predictor of how well – and how long – you’ll live.

That’s because muscles underpin some fundamental aspects of your health, supporting your metabolism, helping control blood sugar, protecting against falls, and even strengthening your immune response.

Many people confuse being active with being strong. But while regularly walking your dog or gardening will boost aerobic fitness, it’s unlikely to build muscle. And this is crucial.

A recent study involving more than 5,000 older women found that those who were stronger had a 30 per cent lower risk of dying prematurely than those with weaker muscles.

Muscle strength was measured by grip strength – and the results also took into account how active they otherwise were, reported JAMA Network Open.

Dietitian Dr Emily Leeming says older adults should aim to eat 1 to 1.2g per kg of their body weight in protein every day

Crucially, better grip strength was linked with a lower risk of early death – even among relatively sedentary women who didn’t meet recommended aerobic activity levels of 150 minutes a week. Yet around two-thirds of us aren’t meeting the recommended two sessions a week of muscle-strengthening. Most experts suggest 20 minutes, yet even five minutes can help – and using resistance bands or exercises at home is just as valuable as any gym session.

Building strong muscles starts with eating enough protein: older adults should aim for 1 to 1.2g per kg of their body weight every day. For someone weighing 70kg (around 11st) that’s the equivalent of 84g of protein – a palm-sized portion of chicken or fish gives you 20-30g; two eggs about 12g; and a 110g pot of Greek yoghurt around 10g.

Plant-based foods – such as beans, tofu, tempeh and lentils are also good sources.

Protein is not the only important nutrient for muscle health. People who ate healthier diets – with plenty of veg, fruit, wholegrains nuts and fish – had better muscle mass and function over time, according to a 2021 study in Osteoporosis International.

That’s because a plant-rich diet may provide a mix of nutrients to support muscle repair as well as dampening excess inflammation.

For example, magnesium (found in spinach, pumpkin seeds and beans) plays a role in muscle function and recovery, while vitamin C (from berries, peppers and citrus fruits) supports collagen production, important for maintaining healthy muscle and connective tissue.

Interestingly, a study published earlier this year in the journal Radiology found that those who ate the most ultra-processed foods had more fat stored inside their thigh muscles, a sign of poorer-quality muscle.