The effect of switching from an unhealthy diet to a healthy diet on life expectancy Original paper

In this cohort study, switching from an unhealthy diet to a healthier diet (in line with the UK’s Eatwell Guide) was estimated to increase life expectancy by several years.

Whether switching from the consumption of a less healthy diet to a healthier diet is associated with an increase in life expectancy.

467,354 participants from the UK Biobank cohort.

In this cohort study, the participants completed a food frequency questionnaire and/or a 24-hour dietary recall at baseline. These data were then used to categorize the participants into quintiles based on their consumption of 13 food groups (whole grains, vegetables, fruit, nuts, legumes, fish, egg, milk and dairy products, refined grains, red meat, processed meat, white meat, and sugar-sweetened beverages).

Analyses were conducted to determine the association between the consumption of each food group with all-cause mortality (ACM), and these results were used to estimate whether switching from an unhealthy or average UK diet to a longevity diet or the UK’s Eatwell Guide diet was associated with an increase in life expectancy.

The longevity diet was based on the quantity of consumption of each food group with the lowest ACM risk. For example, a moderate amount of a food group means that, compared to the quintile with the lowest intake, the risk of ACM was lowest in the second or third (the average intake) quintile, and a high amount of a food group means that, compared to the quintile with the lowest intake, the risk of ACM was lowest in the quintiles with the highest intake (the 4th and 5th quintiles). In contrast, the unhealthy diet was based on the quantity of consumption of each food group with the highest ACM risk.

The analyses were adjusted for potential confounders, including age, sex, socioeconomic status, ethnicity/race, smoking status, physical activity, and BMI.

Based on the associations for the consumption of each food group with ACM risk, the longevity diet was composed of moderate amounts of whole grains, nuts, legumes, fruit, fish, eggs, and white meat; high amounts of milk and dairy and vegetables; and a low amount of red meat, processed meat, sugar-sweetened beverages, and refined grains. In contrast, the unhealthy diet was composed of low amounts of whole grains, vegetables, fruits, nuts, legumes, fish, milk and dairy, and white meat and high amounts of red meat, processed meat, eggs, refined grains, and sugar-sweetened beverages.

It was estimated that switching from an unhealthy diet to a longevity diet would increase life expectancy by 8 years in 40-year-olds and by 4 years in 70-year-olds. Also, it was estimated that switching from an unhealthy diet to an Eatwell Guide diet would increase life expectancy by 6 to 7 years in 40-year-olds and by 3 years in 70-year-olds.

Switching from the average UK diet to a longevity diet was estimated to increase life expectancy by 3 years in 40-year-olds and by 2 years in 70-year-olds. However, switching from the average UK diet to an Eatwell Guide diet was not estimated to increase life expectancy.