A recent scientific review found that reducing total dietary protein or restricting specific amino acids may be associated with improved health and longer life, but nutrition specialists warned against applying the findings as a general recommendation, particularly among older people who face an increased risk of losing muscle mass and strength and having difficulty recovering from illness.
Protein is essential for building and repairing muscles and tissues. It also contributes to the production of enzymes and hormones, supports the immune system and plays multiple vital and neurological roles. Its importance increases with age, when the body gradually begins to lose some muscle mass and strength, potentially affecting movement, balance and the ability to carry out daily activities independently.
At the same time, recent studies have examined the relationship between the amount of protein and the types of amino acids it contains and metabolism, cell growth, inflammation and biological ageing. Some findings suggest that limiting protein or certain amino acids may support cellular repair and longevity, while other research highlights the risks of deficiency, particularly for older people’s muscles, mobility and ability to recover.
Review links protein restriction to longevity
The scientific review was published in Cell Press Blue on 17 August 2026. It concluded that restricting total protein or some essential amino acids may offer health benefits similar to some of the effects associated with calorie restriction. The review was based on an analysis of more than 350 scientific studies examining the impact of these restrictions on health and ageing.
The amino acids examined in the studies included isoleucine and methionine. The findings linked lower protein consumption to increased energy expenditure and the burning of more calories, as well as reduced body fat levels and improved insulin regulation — indicators that may affect metabolic processes associated with ageing.
Lower protein intake was also associated with higher levels of the hormone fibroblast growth factor 21, or «FGF21», which is linked to protecting the body from some changes associated with ageing.
The review found that low-protein diets helped inhibit the «mTORC1» pathway and activate the «GCN2» pathway, two of the main cellular nutrient sensors responsible for regulating cell growth and responses to stress. The researchers believe these changes may prompt cells to direct more resources towards repair and maintenance rather than continuous growth.
Autophagy may also be enhanced. This is a natural process through which cells dispose of damaged or accumulated components, helping them maintain their functions. The review also linked lower protein intake to a reduction in the number of senescent cells, or ageing cells.
These are damaged cells that stop dividing but do not die, and are associated with chronic inflammation and the deterioration that accompanies ageing. The researchers identified three essential amino acids whose reduction may be linked to potential longevity benefits: isoleucine, valine and methionine.
The analysis also indicated that reducing some non-essential amino acids, including tyrosine and cysteine, may provide additional health benefits. However, the findings do not mean that reducing all amino acids is beneficial, as providing sufficient amounts of others, such as glycine, serine and proline, may have a positive health role.
Cellular mechanisms that may explain the potential benefits
Dr Mohamed Hassan, a lecturer at Cairo University’s Faculty of Medicine and a consultant in clinical nutrition and medical pharmaceuticals, said there was no contradiction between studies stressing the importance of protein intake and research examining the benefits of reducing it for healthy ageing. He said the findings must be understood in light of age, health status, the amount of protein and its type, rather than by adopting one rule for everyone.
Hassan added that ageing is accompanied by a natural decline in muscle mass, making it important for older people to obtain enough protein while also doing resistance exercises. He stressed that balancing animal and plant proteins is necessary to benefit from the nutritional properties of both sources.
He warned against applying studies that recommended reducing isoleucine, methionine and valine to improve metabolism and extend life to all humans. He said much of the research in this field had been conducted on animals, making it inappropriate to treat the findings as direct dietary guidance that can be applied to people without further assessment.
Experts warn against applying findings broadly to older people
Dr Rania Ahmed Bassiouni, a researcher in the Department of Nutrition and Food Science at the Food Industries and Nutrition Research Institute of the National Research Centre in Cairo, said older people’s diets require particular attention to their quality, quantity and ability to meet the body’s actual needs.
Bassiouni said maintaining muscle mass and strength was one of the main goals of nutrition for older people, given their direct effect on movement, balance and independence in daily activities. This can be supported by obtaining an appropriate amount of protein alongside physical activity and muscle-strengthening exercises.
She stressed that protein should not be reduced in older people in the name of resisting ageing without assessing each person’s needs, just as there is no guaranteed benefit from consuming too much. She added that current evidence supports the importance of adequate protein for health in later life, while its direct effect on the speed of biological ageing remains under study.
Bassiouni said persistent protein deficiency was the more immediate risk for older people, particularly those with poor appetites or weight loss. As the deficiency continues, the body may lose more muscle and strength, making movement more difficult and increasing the risk of falls. Older people may also need help from others to carry out daily activities.
Recovery from illness may also take longer, particularly when low protein intake coincides with insufficient calorie intake. Addressing this risk does not mean increasing protein without calculation, but requires determining the appropriate amount according to each person’s health and nutritional needs. People with kidney failure require more precise management because the appropriate amount of protein is linked to the stage of the disease and nutritional status.
Higher intake may harm some patients, while severe restriction can lead to malnutrition and increased muscle weakness. Protein needs should therefore be determined according to kidney function, coexisting diseases and activity levels, with monitoring of weight, appetite and muscle strength. Not all older people need the same amount.
Protein needs vary according to health, kidney function and activity
According to Bassiouni, a healthy person generally needs between 1 gram and 1.2 grams of protein per kilogram of body weight per day. The required amount may increase during illness or recovery, depending on an assessment of the person’s condition. Having a chronic disease alone does not require protein intake to be increased or reduced. A person with diabetes or heart disease who has normal kidney function does not need to reduce protein simply because they have the disease.
The priority is to choose suitable sources and adjust the other components of the diet according to health status, particularly calorie and carbohydrate intake for people with diabetes. Suggested sources include beans, lentils, fish, low-fat poultry and unsweetened dairy products, while processed meat, salt and saturated fats should be limited.
For people with kidney failure who are not on dialysis, the usual recommendation in the moderate and advanced stages is about 0.8 grams of protein per kilogram of body weight per day. Regarding the relationship between protein and brain function, Bassiouni said protein provides amino acids involved in building and repairing tissues, as well as producing some substances responsible for communication between nerve cells.
However, increasing protein in the diet does not necessarily improve memory or protect against dementia. Some follow-up studies have recorded less decline in memory and cognitive abilities among people who consume protein, particularly from plant sources such as beans, lentils and chickpeas. But this finding cannot be attributed to protein alone, as the participants may have been more active or generally followed a better diet.
At the same time, other studies found no clear benefit from increasing protein intake. Protein-rich diets or supplements are therefore not considered a proven means of preventing Alzheimer’s disease or other types of dementia. The priority remains meeting older people’s nutritional needs through varied meals, while identifying and treating any nutritional deficiencies.
Bassiouni highlighted the importance of vitamin «B12» for older people because a deficiency may affect the nerves and cognitive abilities. The deficiency may result from a decline in some older people’s ability to absorb the vitamin, in which case replacement and treatment are necessary. Taking supplements without a deficiency does not necessarily provide additional protection for memory.
The researcher proposed a daily meal plan combining plant and animal protein. It includes a meal containing four tablespoons of mashed fava beans blended to make swallowing easier, with a teaspoon of olive oil, a little lemon and cumin, one well-boiled egg, and one-quarter to one-half of a baladi loaf, according to its size and the older person’s needs.
Cucumber and tomato slices can be added to this meal, or soft vegetables can be served if the older person has difficulty chewing. This adjustment takes into account the person’s ability to eat, rather than focusing on nutritional content separately from swallowing or chewing problems that may affect the amount of food consumed.
Another meal includes between 100 and 120 grams of grilled mackerel after cooking, with the bones carefully removed, seven tablespoons of cooked rice and a medium plate of finely chopped salad. The salad can be replaced with well-cooked vegetables if the older person has swallowing problems.
The plan also includes 80 grams of low-salt cottage cheese, a teaspoon of olive oil, one-quarter to one-half of a baladi loaf according to the loaf’s size and individual needs, as well as leafy vegetables such as rocket and lettuce. These meals combine plant and animal protein to help maintain muscle mass and strength.
Dairy products also provide calcium, while mackerel provides vitamin «D», which supports bone health, as well as vitamin «B12», which is important for the nerves and the formation of blood cells. The plan’s ingredients provide iron and folate, which contribute to blood-cell formation. Fish provides omega-3 fatty acids, while olive oil supplies unsaturated fats as part of a dietary pattern that supports heart health.
Vegetables, fruit and beans provide fibre that helps regulate bowel movements, as well as potassium and magnesium, which contribute to muscle and nerve function. Depending on the type, vegetables and fruit also provide vitamin «C», which helps the absorption of plant-based iron, vitamin «A» compounds that are important for vision and immunity, and vitamin «K», which contributes to normal clotting and bone health.
Bread and rice provide the energy needed for daily activity. The adequacy of the dietary plan remains linked to the quantities of its ingredients, the older person’s needs and their health status, confirming that balancing muscle protection with the potential benefits of protein restriction requires individual assessment, not a general and uncalculated reduction.
