Researchers here look at simple, broad dietary changes and process existing data to see the expected effects on human life expectancy. They suggest that the difference between a poor diet and a good diet maintained across much of life is a decade of life expectancy, a surprisingly large number give that studies suggest that many common forms of aerobic exercise, such as jogging, appear to top out at an additional five years of life expectancy. When looking at high level data for diet, it is worth remembering that calorie intake is probably affected, and reduced calorie intake has a sizable effect on health. Another point to consider is how diet influences aging of the gut microbiome, and the presently unknown degree to which that is an important mediating factor in the effects of dietary composition on life span.
Based on meta-analyses and data from the Global Burden of Disease study, we used life table methodology to estimate how life expectancy (LE) changes with sustained changes in the intake of fruits, vegetables, whole grains, refined grains, nuts, legumes, fish, eggs, milk/dairy, red meat, processed meat, and sugar-sweetened beverages. We present estimates for an optimized diet and a feasibility approach diet. An optimal diet had substantially higher intake than a typical diet of whole grains, legumes, fish, fruits, vegetables, and included a handful of nuts, while reducing red and processed meats, sugar-sweetened beverages, and refined grains. A feasibility approach diet was a midpoint between an optimal and a typical Western diet.
A sustained change from a typical Western diet to the optimal diet from age 20 years would increase LE by more than a decade for women from the United States (10.7 years) and men (13.0 years). The largest gains would be made by eating more legumes (females: 2.2; males: 2.5), whole grains (females: 2.0; males: 2.3), and nuts (females: 1.7; males: 2.0), and less red meat (females: 1.6; males: 1.9) and processed meat (females: 1.6; males: 1.9). Changing from a typical diet to the optimized diet at age 60 years would increase LE by 8.0 years for women and 8.8 years for men, and 80-year-olds would gain 3.4 years. Change from typical to feasibility approach diet would increase LE by 6.2 years for 20-year-old women from the United States and 7.3 years for men.
In conclusion, a sustained dietary change may give substantial health gains for people of all ages both for optimized and feasible changes. Gains are predicted to be larger the earlier the dietary changes are initiated in life.