Amarpreet Singh has been drinking protein shakes since he was 16.

The 30-year-old, who lives in London and works in banking, started going to the gym at a time when he says protein supplements were mostly associated with bodybuilders.

Fourteen years later, shakes are still part of his routine, but they have become considerably more expensive.

He says a 4.5kg bag of the whey protein he buys cost around £60 in 2020.

By last year, the price had gone up to £120, though he managed to get one from eBay for £90.

Now the same bag is £170.

“I was a bit gobsmacked,” he says.

Among his gym friends, the rising prices have even been given a nickname – “proteinflation”.

Over the years, protein powders and shakes have attracted a much broader customer base, while food manufacturers now offer high-protein versions of everything from bagels to water.

Evie Lewis is a more recent buyer of protein powder.

The 19-year-old University of Manchester student began using it a few months ago because she felt she wasn’t getting enough protein in her diet.

“You hear a lot more about protein now on social media,” she says.

But at £32.99 for a 420g tub, she’s feeling the high price and tries to make the product stretch.

“I’ve been rationing it and using less than what’s suggested,” she admits.

Max Longman, 32, from Manchester, works in real estate and has been taking protein supplements for 10 years, originally to help him gain weight.

He now drinks a protein shake every day and says his monthly spending on whey protein has risen from around £45 a year ago to £60 now.

“Loads of foods have protein added to them now. Up until a few years ago, I’d never heard of high-protein yoghurt, and now I eat it three or four times a week,” he says.

More recently, weight-loss drugs such as Wegovy and Mounjaro have added another source of demand.

People taking these drugs typically eat less, and are often encouraged to make sure they get enough protein while losing weight to help preserve muscle.

But that growing appetite for protein is running up against a problem – supply has not kept pace.

And the result has been a sharp rise in the wholesale price of some key ingredients, and consumers are feeling the squeeze.

According to global market intelligence platform Expana, the European price of one widely used type of high-protein whey was 130% higher in late August than a year earlier, and more than four times its level three years ago.

There is no equivalent UK measure, but Expana says the UK market is closely linked to mainland Europe, where some British businesses source their whey protein.

Other dairy proteins have also become more expensive, with another type of whey protein up 60% over the year, while one type of milk protein concentrate was up 80%.

Manufacturers say that increasing production takes time and is costly, as producing high-protein whey requires specialist processing and drying equipment.

So some are starting to adapt what they make, by changing recipes or looking for cheaper sources of protein.

Warrior, a UK sports nutrition company, is one of those looking for alternatives.

“Our whey protein powder was £12.50 on the shelf last year. We’ve put that up to £17.99 and we’re still subsidising that from other aspects of the business,” says its founder Kieran Fisher.

The company is now launching a product using other sources of protein, which Fisher says costs around half as much as whey.

The effects are also being felt outside the fitness market.

Dairy proteins are used in infant formula, and Expana says higher dairy protein costs have contributed to price rises there too.

There are, however, early signs that the market is starting to adjust.

Wholesale prices for high-protein whey have begun to level off over the past couple of months, although they remain much higher than they were a few years ago.

For now though, the higher prices aren’t putting off Max.

“It feels like protein is so important now, a lot more than it used to be. It’s pushed out everywhere,” he says.

“If you’re doing exercise and not taking any, you feel like you wouldn’t be recovering properly.”

But for students like Evie, managing on a much tighter budget, it’s a different story.

“It was affordable on my gap year [when she was working], but now I’m at university, I don’t think I’ll continue buying it. It’s not a necessity right now,” she says.

Amarpreet says he will continue buying protein, but admits “it’s becoming a luxury”. He says £170 for a bag is too much for him, so he’s switching to a cheaper brand, which he can get for about £100 a bag.