Improving diet over time consistently reduces all-cause and cardiovascular mortality, according to an analysis of two large U.S. databases.

Researchers examined the association between dietary change over a 12-year period (1986-1998) and subsequent mortality during a further 12 years of follow-up (1998-2010), using data for 47,994 women participating in the Nurses’ Health Study and 25,745 men participating in the Health Professionals Follow-Up Study. They calculated dietary quality using three different methods: the Alternate Healthy Eating Index-2010 score, the Alternate Mediterranean Diet score, and the Dietary Approaches to Stop Hypertension (DASH) diet score.

There were 5,967 deaths during 544,973 person-years of follow-up among the women and 3,979 deaths during 286,402 person-years of follow-up in the men, said Mercedes Sotos-Prieto, PhD , of the department of nutrition at the Harvard T. H. Chan School of Public Health, Boston, and her associates.

Through numerous analyses of the data, they found a consistent inverse relationship between dietary quality and mortality. Overall, a 20-percentile increase in dietary quality over time was associated with an 8%-17% reduction in all-cause mortality, regardless of which scoring method was used. In contrast, a similar decline in dietary quality was associated with a 6%-12% increase in mortality.

“The pooled hazard ratios among participants with the greatest improvement in diet quality (13%-33% improvement), as compared with those whose diet quality remained relatively stable (0%-3% improvement) in the 12-year period, were the following: 0.91 according to changes in the Alternate Healthy Eating Index score, 0.84 according to changes in the Alternate Mediterranean Diet score, and 0.89 according to changes in the DASH score,” the investigators said (N Engl J Med. 2017 Jul 13. doi: 10.1056/NEJMoa1613502 ).

In addition, participants who maintained a high-quality diet throughout the study period also reduced their risk of death from any cause by 9%-14%, compared with those who maintained a poor-quality diet over time.

“Our findings provide support for the recommendation of the 2015 Dietary Guidelines Advisory Committee that it is not necessary to conform to a single diet plan to achieve healthy eating patterns. These three dietary patterns, although different in description and composition, capture the essential elements of a healthy diet. Common food groups in each score that contributed the most to improvements were whole grains, vegetables, fruits, and fish or n-3 fatty acids,” Dr. Sotos-Prieto and her associates noted.