The study created a model of what might happen to a man or woman’s longevity if they replaced a “typical Western diet” focused on red meat and processed foods with an “optimized diet” focused on eating less red and processed meat and more fruits and vegetables, legumes, whole grains and nuts.
Focusing on a healthier diet could also lengthen the lives of older adults, the study said. By starting at age 60, a woman could still increase her lifespan by eight years. Men starting a healthier diet at age 60 might add nearly nine years to their lives.
A plant-based eating style could even benefit 80-year-olds, the study said: Men and women could gain about 3.5 years of extra life from dietary changes.
“The notion that improving diet quality would reduce the risk of chronic disease and premature death is long established, and it only stands to reason that less chronic disease and premature death means more life expectancy,” said Dr. David Katz, a specialist in preventive and lifestyle medicine and nutrition, who was not involved in the study.
“What they define as an ‘optimal’ diet is not quite optimal; it’s just a whole lot better than ‘typical,'” Katz said, adding that he felt diet could be “further improved, conferring even greater benefits.”
“My impression is that their ‘much improved’ diet still allowed for considerable doses of meat and dairy,” Katz said, adding that when his team scores diet quality objectively, “these elements are at quite low levels in the top tier.”
A model of longer life
The largest gains in longevity were found from eating more legumes, which include beans, peas and lentils; whole grains, which are the entire seed of a plant; and nuts such as walnuts, almonds, pecans and pistachios, the study found.
The CDC study found that only 12% of adults consume 1½ to 2 cups of fruit each day, which is the amount recommended by the federal Dietary Guidelines for Americans. Only 10% of Americans eat the recommended 2 to 3 cups of vegetables each day, including legumes.
Over 50% of Americans fail to eat the 5 grams (about a teaspoon) of recommended nuts and seeds each day, the guidelines said.
Nuts, seeds, legumes and whole grains contain more than just protein. They include healthy fats, vitamins, minerals and antioxidant “phytochemicals” that have been associated with lower risk of chronic diseases.
Red and processed meats
Eating less red and processed meat such as bacon, sausage and preserved deli meats was also linked to longer life.
Replacing red and processed meats with lean poultry, fish and plant proteins is one way to improve a diet quickly, experts say.
Plant proteins include soybeans (edamame), chickpeas, lentils and other legumes, tofu, tempeh, nuts, seeds, and whole grains like quinoa. Some vegetables, like broccoli, also contain higher levels of protein.
A 2020 study which tracked more than 37,000 middle-aged Americans found those who ate the most plant protein were 27% less likely to die of any cause and 29% less likely to die of coronary heart disease than people who ate the least amount of plant protein.