Harvard researchers have discovered that even modest dietary improvements can make a difference in health and promote longevity when sustained over time. This is encouraging news for those who find the idea of a complete diet overhaul intimidating.

Our findings underscore the benefits of healthy eating patterns including the Mediterranean diet.- Mercedes Sotos-Prieto

The new study is the first to show that boosting diet quality over at least 12 years is linked to significantly lower total mortality, as well as lower cardiovascular mortality. It defines quality in the diet as eating more fruits, vegetables, nuts, whole grains and fish while reducing intake of sugary beverages, red meat and processed meat.

“Overall, our findings underscore the benefits of healthy eating patterns including the Mediterranean diet and the DASH diet. Our study indicates that even modest improvements in diet quality could meaningfully influence mortality risk and conversely, a worsening diet quality may increase the risk,” said lead author Mercedes Sotos-Prieto, who worked on the study while a postdoctoral fellow in the Harvard Chan School Department of Nutrition and who is currently an assistant professor of nutrition at Ohio University.

Sotos-Prieto and her colleagues evaluated data from 74,000 adults to ascertain the effect of diet on death risk. The data, which covered a 12-year period from 1986 to 1998, came from two studies: the Nurses’ Health Study and the Health Professionals’ Follow-up Study. Participants were required to provide information about their diet, health and lifestyle at regular intervals. The researchers followed them for 12 subsequent years from 1998 to 2010 to document fatalities.

Three scoring methods were used to assess diet quality: the Alternate Mediterranean Diet Score, the 2010 Alternate Healthy Eating Index, and the Dietary Approaches to Stop Hypertension (DASH) diet score. Each method assigns higher scores to nutritious food and lower scores to less healthy foods.

Analysis of the findings showed improved diet quality over 12 years was connected with a lower death risk in the subsequent 12 years, regardless of what scoring method was used. Foods that contributed the most to diet quality included fruits, vegetables, whole grains, fish and n-3 fatty acids.

Most remarkably, a 20-percent boost in diet quality scores was linked to an 8- to 17-percent decrease in the risk of death. Conversely, a reduction in diet quality was tied to a 6- to a 12-percent rise in the death risk.

Participants who maintained a higher food quality score on any of the three healthy diet measurement methods over 12 years had a 9- to 14-percent reduction in death incidence from any cause. In addition, those who started out the study with relatively unhealthy diets but improved their eating habits the most also had a significantly lower risk of death in subsequent years.

The 20-percent improvement is a modest amount that can be attained in a variety of ways. In an interview with Olive Oil Times, Sotos-Prieto provided examples of how one simple daily swap from less healthy fare to more healthy fare can boost the nutrition of a diet enough to result in an increase in longevity. Any of the following exchanges can constitute a 20-percent increase in quality of food intake:

  • Increasing nuts and legumes up to one serving per day and not consuming sugary beverages and fruit juice during the day (One serving is 1 oz of nuts or 1 tablespoon of peanut butter)
  • Swapping sugar and sweetened beverages daily for four servings of fresh fruit per day (One serving is 1 medium piece of fruit or 1/2 cup of berries)
  • Increasing vegetable consumption to five servings per day and decreasing red and processed meat consumption to 1.5 servings per day to little consumption (One serving of veggies is 1/2 cup of vegetables or 1 cup of green leafy vegetables and one serving is 4 oz of unprocessed meat or 1 1/2 oz of processed meat)

“Our results highlight the long-term health benefits of improving diet quality with an emphasis on overall dietary patterns rather than on individual foods or nutrients. A healthy eating pattern can be adopted according to individuals’ food and cultural preferences and health conditions. There is no one-size-fits-all diet,” said Frank Hu, professor, and chair of the Harvard Chan School Department of Nutrition and senior author of the study.

The study was published in the New England Journal of Medicine.


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