Protein is having a moment. But is more always better?
May 2026 | 3 minute read
If social media is anything to go by, you'd be forgiven for thinking you can't eat too much protein.
Protein coffees. Protein yoghurt. Protein water. Protein chocolate. Add to that the growing number of influencers recommending high-protein diets, and it's easy to believe that more protein automatically means better health.
Then you'll come across someone claiming that too much protein damages your kidneys, weakens your bones or "stresses" your liver.
So, who's right?
The evidence suggests neither extreme tells the full story.
For most healthy adults, protein is essential for healthy ageing. But once your body's needs are met, consuming substantially more is unlikely to provide additional benefits.
Why protein matters
Protein provides the building blocks for muscles, bones, skin, enzymes, hormones and many other tissues throughout the body.
As we age, particularly during and after menopause, maintaining muscle becomes more difficult. Adequate protein, combined with regular resistance training, helps preserve muscle mass, supports recovery from exercise and maintains physical function.
For many older adults, increasing protein intake from too little to enough is beneficial. The key word is enough.
How much protein do you actually need?
Protein requirements vary depending on your age, health and activity level.
*Individual requirements vary according to health conditions, training load and personal goals.
Many people can comfortably meet these targets through food without needing protein supplements.
You may have seen advice suggesting up to and around 2.2 g of protein/kg of body weight each day (around 150 g/day for someone weighing 70 kg) and protein intakes around this level may be appropriate for some people, including:
- Competitive strength and physique athletes.
- Athletes training at very high volumes.
- Lean athletes trying to preserve muscle while in a calorie deficit.
However, current evidence does not suggest that most healthy adults need this much protein to support muscle, bone or general health.
For most active adults, including those undertaking regular resistance training, around 1.2–1.6 g/kg/day appears sufficient to maximise most of the benefits associated with protein intake. Beyond this, additional benefits become smaller for most people.
Does protein damage healthy kidneys?
This is one of the most common concerns. Current evidence does not show that higher-protein diets damage kidney function in healthy adults.
Protein metabolism increases the amount of waste products the kidneys need to filter. Healthy kidneys adapt to this increased workload, and this normal physiological response has not been shown to cause kidney disease.
However, the advice is different for people with established chronic kidney disease. In that situation, protein intake should be individualised under the guidance of a doctor or Accredited Practising Dietitian.
Does protein harm the liver?
Another common claim is that high-protein diets "stress the liver."
For healthy people, there is little evidence to support this. People with advanced liver disease may require specialised nutrition advice, but this should not be generalised to healthy adults.
Does protein weaken your bones?
This idea comes from a theory known as the acid-ash hypothesis.
Researchers once believed that animal protein increased acidity in the body, causing calcium to be released from bones to neutralise the acid.
It was a plausible theory. However, more recent research has shown that while higher protein intakes can increase calcium excretion in urine, they also increase calcium absorption from the intestine. Overall, the evidence suggests that adequate protein is neutral or beneficial for bone health, particularly when calcium intake is sufficient and resistance exercise is included.
Bone itself is also around 50% protein by volume. The collagen matrix forms the framework upon which calcium and other minerals are deposited. Protein is an essential part of healthy bone not an enemy of it.
What happens if you consistently eat more protein than you need?
Unlike carbohydrate, excess protein is not stored in the body. Extra amino acids are broken down. Some are used to produce energy and, if your total energy intake consistently exceeds your needs, the excess energy can contribute to body fat storage—just as excess energy from carbohydrate or fat can.
Very high-protein diets may also:
- Reduce fibre intake if they replace fruit, vegetables, legumes and whole grains.
- Increase the likelihood of constipation if fibre intake is low.
- Increase fluid requirements because protein metabolism produces nitrogen-containing waste products that are excreted in urine.
- Become unnecessarily expensive.
- Be difficult to sustain over the long term.
These are practical downsides rather than evidence that protein itself is harmful.
So, is there an upper limit?
There is no single protein intake above which protein suddenly becomes harmful for healthy adults.
Current evidence suggests that protein intakes above the Recommended Dietary Allowance are generally safe for healthy adults and may be beneficial in some circumstances, particularly resistance training, healthy ageing and preserving muscle during weight loss.
However, once your requirements are met, consuming substantially more appears to offer diminishing returns.
More is not always better.
The bigger picture - Protein is only one part of healthy ageing.
The strongest evidence continues to support:
- Regular resistance training.
- Adequate (not excessive) protein intake.
- Sufficient calcium and vitamin D.
- Plenty of vegetables, fruit, legumes and whole grains.
- Good sleep.
- Not smoking.
- Limiting excessive alcohol intake.
No single nutrient can compensate for an otherwise unhealthy lifestyle.
The bottom line
Protein deserves its place on the plate, particularly during midlife and beyond.
Despite what social media might suggest, there is no compelling evidence that healthy adults need to consume extremely high amounts of protein to optimise their health. Equally, there is little evidence that sensible protein intakes damage healthy kidneys, liver or bones.
Rather than chasing the highest possible protein intake, aim for the amount that meets your individual needs within a balanced diet that includes plenty of whole foods.
As with most aspects of nutrition, the healthiest approach is usually found somewhere between the extremes.
For most healthy adults, adequate protein supports muscle, bone and healthy ageing. Extremely high intakes offer few additional benefits and may simply crowd out other nutritious foods. People with chronic kidney disease, advanced liver disease or other conditions affecting protein metabolism should seek personalised medical advice before making major dietary changes.
References
Darling AL, Manders RJF, Sahni S, et al. (2019). Dietary protein and bone health across the life-course: An updated systematic review and meta-analysis over 40 years. Osteoporosis International, 30(4), 741–761.
Rizzoli R, Biver E, Bonjour JP, et al. (2018). Benefits and safety of dietary protein for bone health—An expert consensus paper. Osteoporosis International, 29(9), 1933–1948.
Shams-White MM, Chung M, Du M, et al. (2017). Dietary protein and bone health: A systematic review and meta-analysis from the National Osteoporosis Foundation. American Journal of Clinical Nutrition, 105(6), 1528–1543.
Zittermann A, Schmidt A, Haardt J, et al. (2023). Protein intake and bone health: An umbrella review of systematic reviews for the evidence-based guideline of the German Nutrition Society. Osteoporosis International, 34(8), 1335–1353.
Jäger R, Kerksick CM, Campbell BI, et al. (2017). International Society of Sports Nutrition Position Stand: Protein and Exercise. Journal of the International Society of Sports Nutrition, 14, 20.
Morton RW, Murphy KT, McKellar SR, et al. (2018). A systematic review, meta-analysis and meta-regression of protein supplementation on resistance training-induced gains in muscle mass and strength in healthy adults. British Journal of Sports Medicine, 52(6), 376–384.
Helms ER, Aragon AA, Fitschen PJ. (2014). Evidence-based recommendations for natural bodybuilding contest preparation: Nutrition and supplementation. Journal of the International Society of Sports Nutrition, 11, 20.
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