Ask Dr Adam: Can My Body Only Absorb a Certain Amount of Protein?
Thanks to the rise of social media nutrition experts, a swathe of best-selling cookbooks and an influx of gym-focussed foods in the supermarket, protein has become something of a diet obsession in recent years.
And with good reason too: protein is the building blocks of our muscles. Getting enough of this vital macronutrient can not only help to maintain muscle strength as you age, but also boost metabolism, improve bone density and support heart health too.
Government guidelines suggest that women should aim for roughly 45g of protein per day and men should eat around 55.5g, but if youāre currently working out with the goal of getting stronger, adding extra protein into your diet is often a necessary step to seeing results.
But when it comes to protein, how much is too much? Is it possible that your body can only absorb a certain amount, meaning all those extra grams youāre carefully consuming through high-protein snack bars and gym yoghurts are essentially wasted money?
As always, we asked our Head of Nutrition, Dr Adam, to clue us in on the factsā¦
How much protein can the body absorb?
Studies have shown that once you hit around 20 to 25g of protein in one sitting, your body doesnāt continue to increase protein synthesis (the process where your muscles use protein to repair and grow) any further, even if youāve just exercised. Instead, any excess amino acids are either used for energy or excreted in your pee.
This effect is especially true if youāre consuming protein without following it up with exercise. After eating protein, your muscles can only process so much before theyāre āfull,ā meaning they hit their maximum absorption capacity. Typically, this happens around two hours ā post-consumption – a phenomenon thatās known as the āmuscle fullā effect.
For individuals with more muscle mass or higher body weight, the threshold for protein absorption might be slightly higher, around 30 to 35g per sitting. But thereās still a limit: likely between 0.25g to 0.35g per kg of body weight.
Does exercise change things?
Yes, it does. When you do resistance training, your body becomes much better at using protein to build muscle. In fact, exercise can nearly double the amount of muscle-building that happens compared to just eating protein alone.
That means eating a bit more than 20 to 25g of protein after a workout might be helpful, but the benefits donāt keep increasing at the same rate. For example, going from 10g to 20g of protein gives you a big boost, but jumping from 20g to 40g only gives you a small extra gain (roughly 20 to 30% more).
This info comes mostly from studies using protein supplements like whey and looking at muscle growth over the first four hours after eating.
Does having protein in one sitting make a difference?
A 2023 study found that eating a large amount of protein, up to 100g in one go, can still boost muscle-building, as long as you take it over a longer time period; in this case, 12 hours.
So, having a big serving of protein might still be useful, especially if itās spread out slowly in your body. You even see this in nature, with predators feasting on huge amounts of protein after a kill, with their bodies making use of the protein hit over time.
Another consideration is the form of protein youāre eating. How digestible it is, and whether youāre eating it in a meal that contains fat and fibre, will dictate how readily amino acids are delivered into the blood.
Supplements may max out at 20 to 25g per dose over a couple of hours, but youāll likely cope with higher amounts in a mixed meal because itās delivered more slowly.
Finally, age and training status are also important to think about. Most protein-feeding studies use young, healthy, untrained people. Therefore, you may well need higher amounts to overcome anabolic resistance as you age, or to trigger additional gains if youāre already trained.
