Experts issue warning on protein bars as new study raises concerning 'question'

For seasoned gym-goers and newbies alike, hitting protein consumption goals can be a challenge. Conventional wisdom says that to effectively build muscle, it's best to aim for 1.6 to 2.2 grams of protein per kilogram of body weight per day - a number that's generally quite achievable by incorporating more high protein ingredients like chicken, fish, tofu and yogurt into meals.

However, plenty of gym buffs reach for a protein bar for an extra shot of the good stuff while on the go, with some bars boasting up to 20g of protein wrapped up in a tasty, chocolatey treat. If that seems almost too good to be true, scientists suggest you might be right.

While bulking out your diet's protein levels with whole foods is always recommended, there's nothing inherently wrong with adding a protein shake or bar to round out your day or add a little boost post-workout. But they're not all created equal, and a recent analysis of 1,641 protein bars provides some food for thought the next time you reach for a protein bar over a dollop of Greek yogurt for a protein-filled snack.

Not all protein bars are created equal (skynesher/Getty Images)

The study showed that, actually, the quality of protein in most bars on the market isn't ideal for building muscle.

For the study, researchers analysed the protein content, source, and nutritional quality of widely-available protein bars, using data from OpenFoodFacts.org. They divided the bars into four categories based on their protein sources: plant only (pea and rice), animal only (milk proteins), mix of animal (milk and egg) and plant (soy), and mix of animal (milk and collagen) and plant (soy), and tested amino acid composition and digestibility using a process that mimics the digestion process in a laboratory setting.

The findings were quite astonishing: Although 81% of the protein bars were considered high in protein, when the protein sources were processed into bar form, digestibility dropped drastically - to as low as 47%. That means that not all of the protein said to be in the bars is actually able to be digested and absorbed by the body, so in all likelihood you aren't getting the full 20g of protein from the bar.

According to the study, "the low numbers are most probably due to application of lower-nutritional-quality proteins (such as collagen) and of other ingredients such as carbohydrates, fats and fibres, that might deteriorate the bioaccessibility of essential amino acids."

Getting enough protein is important for gaining muscle, but it's important to choose the right protein sources (svetikd/Getty Images)

The best bar for bioaccessibility was the one containing only milk proteins, sourced from whey and milk protein concentrate, but the content didn't come close to the levels in its isolated form.

"Therefore, we suggest the consumption of protein bars as a part of a complete diet," the study concluded.

"We think that these results raise the question of the nature of the true protein nutritional quality of high protein products and generate the need for more data to reveal the relationship between protein sources, the effect of additional ingredients and protein nutritional quality of protein-associated food products."

So, maybe it's better to chow down on a chicken breast post-gym rather than a chocolatey protein treat if you want to maximise your gains.