Protein is an essential nutrient that plays a crucial role in maintaining good health. However, recent research suggests that the amount of protein we consume may also have an impact on our longevity and all-cause mortality.
A study funded by the National Institutes of Health (NIH) found that a high-protein diet during middle age was associated with higher mortality 1. In adults over 65, however, a high-protein diet was linked to lower mortality 1. The study analyzed information on more than 6,800 U.S. adults, ages 50 and over, from the Third National Health and Nutrition Examination Survey (NHANES III) 1.
The researchers found that adults in the 50 to 65 group who reported a high protein intake had a 75% increase in overall mortality and were 4 times more likely to die from cancer during the following 18 years than those in the low protein group 1. The moderate-protein diet was associated with a 3-fold increase in cancer mortality compared to the low-protein diet 1. These associations were only found when the proteins were derived from animal, rather than plant, sources 1.
Conversely, in participants ages 65 and older, those who consumed high amounts of protein had a 28% lower risk of dying from any cause and a 60% lower risk of dying from cancer 1. These associations weren’t influenced by whether the protein was derived from animal or plant sources 1.
Another study published in EBioMedicine found that a reduced protein intake or low-protein/high-carbohydrate diet plays a critical role in longevity and metabolic health 2. Additionally, specific amino acids (AAs), including methionine or branched-chain AAs (BCAAs), are associated with the regulation of lifespan/ageing and metabolism through multiple mechanisms 2.
Therefore, methionine or BCAAs restriction may lead to benefits on longevity and metabolic health 2. Moreover, epidemiological studies show that a high intake of animal protein, particularly red meat, which contains high levels of methionine and BCAAs, may be related to the promotion of age-related diseases 2.
A systematic review and meta-analysis of prospective cohort studies published in The BMJ found that intake of total protein was associated with a lower risk of all-cause mortality 3. Intake of plant protein was significantly associated with a lower risk of all-cause mortality and cardiovascular disease mortality, but not with cancer mortality 3. Intake of total and animal protein was not significantly associated with the risk of cardiovascular disease and cancer mortality 3.
Another study published in the European Journal of Epidemiology found that a higher plant protein intake was associated with lower all-cause and cardiovascular disease (CVD) mortality 4. For all-cause mortality, the highest versus lowest intake of plant protein was associated with a 7% lower risk, and for CVD mortality, the highest versus lowest intake was associated with a 14% lower risk 4.
To add additional clarity: Amino acids are the building blocks of protein, and there are 20 different kinds of amino acids that your body needs to function correctly 5. These 20 amino acids combine in different ways to make proteins in your body 5. Your body makes hundreds of amino acids, but it can’t make nine of the amino acids you need 5. These are called essential amino acids, and you must get them from the food you eat 5. The nine essential amino acids are histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan, and valine 5. Although all nine essential amino acids are present in plant proteins, the levels vary and specifically methionine levels tend to be much lower in plant-based protein sources 6.
In conclusion, controlling protein intake may be a key to longevity. Consuming moderate to high levels of animal protein may increase cancer risk and mortality in middle-aged adults, while elderly individuals may benefit from a higher protein intake of any source. But it appears to be potentially more important to consider the source of protein. Protein is essential for increasing strength and muscle growth because it provides the amino acids your body needs to build and repair muscle 7.
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