Do you live longer by eating less protein, or more?
The ideal protein level differs by stage of life: in middle age less appears to be better, while after the age of 65 getting enough protein is protective. What is clear: choose plant-based protein sources as much as possible and limit processed red meat.
The answer depends strongly on your age. In a large study where people were followed for many years, those aged 50 to 65 with a high protein intake had a 75% greater chance of dying early and a fourfold greater chance of dying from cancer, compared with peers who ate little protein. For diabetes the risk was fivefold, regardless of age. Above the age of 65 the picture reverses: higher protein intake was associated with a lower chance of cancer and early death. At older ages the body simply needs more protein to maintain muscle and strength.
What you eat matters at least as much as how much protein you take in. Getting more plant protein and less animal protein, even replacing just 3% of your daily calories, was linked to 10% fewer deaths and 11 to 12% fewer deaths from heart and blood vessel disease. People who replaced processed meat products with plant-based protein sources saw a 34% lower risk of death. People who eat more plant-based foods and less processed red meat die less often on average, but whether the protein itself is the cause has not been proven.
There is no researched supplement dose for a longer life: it is about an eating pattern, not a pill or powder. You do not buy a supplement labelled 'protein' for this purpose. What is certain is that too little protein is also a risk, especially after the age of 65: muscle loss and frailty shorten life expectancy. One review that cleared high protein intake of harm was written by authors with demonstrable ties to the meat and dairy industry; weigh those dissenting voices with some caution.
This answer is based on several large studies in which tens of thousands of people were followed for many years, supplemented by reviews of animal and laboratory research and one further review. The age-dependent findings come from a study of more than 6,000 Americans over 18 years; the findings on plant versus animal protein come from studies with more than 500,000 participants combined. The association may reflect cause and effect, but that has not been established: people who eat a lot of plant protein also live differently in other ways. For the mechanisms involving amino acid restriction, the evidence in people is still thin; animal studies are more convincing. A review with conflicting interests (ties to the meat and dairy industry) played down the harms of high-protein diets; the researchers themselves acknowledged a possible conflict of interest.
Does eating a low-protein diet extend your life, or does that only apply to mice?
Eating less animal protein appears beneficial in middle age, but after the age of 65 getting enough protein is actually important. Replace animal protein with plant protein where possible, and discuss major dietary changes with your doctor.
Does eating less help you live longer?
In laboratory animals the effect on lifespan is well established, but in healthy humans direct evidence is lacking. A moderate and sustainable eating pattern is wiser than extreme restriction; discuss major changes to your diet with a dietitian or doctor.
Do older adults need more protein than younger people?
Older adults likely need more protein than the standard guideline of 0.8 grams per kilogram suggests. As a healthy older adult, aim for 1.0 to 1.2 grams per kilogram per day, spread well across meals, and combine this with resistance training where possible.
Do you live longer on a vegetarian or plant-based diet?
A good-quality plant-based diet is linked to fewer early deaths. But strictly vegetarian or vegan eating has not been proven to be better than a varied diet that includes occasional meat or fish.
How much protein can your body use in a single meal?
Your body can use more than 20-25 grams of protein per meal, especially when that protein is combined with carbohydrates and fats. Spread your intake across four meals of approximately 0.4 grams per kilogram of body weight for the best results.
Is eating a lot of protein bad for your kidneys?
For healthy people, kidney damage from eating a lot of protein has not been demonstrated. If you already have kidney disease, the amount and type of protein matter: discuss this with your doctor or dietitian.