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Even modest changes in diet can, over the long run, reduce the risk of premature death, study suggests

The changes that appeared to be most important were those that involved eating more whole grains, fruits, vegetables and fish.

People who improved their diet-quality scores during the first 12 years of the study were at reduced risk of dying during the subsequent 12 years.
REUTERS/Lucy Nicholson

People who improve their diet over time to include more whole grains, vegetables, fruits and fish lower their risk of premature death, new research suggests.

Yes, yes, this may seem like a “duh” study, but according to the Harvard University researchers who did the research, this is the first study to show that switching to a more healthful eating plan can, over the long run (more specifically, a dozen years), help reduce the risk of dying early, particularly from heart disease.

Interestingly, it also showed that it’s the overall dietary pattern that’s important, rather than individual nutrients.

“Our study indicates that even modest improvements in diet quality could meaningfully influence mortality risk and conversely, worsening diet quality may increase the risk,” said Frank Hu, the senior author of the study and chair of the Harvard Chan School Department of Nutrition, in a released statement.

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Study details

For the study, Hu and his colleagues analyzed data collected from almost 74,000 participants in two decades-old studies: 47,994 women from the Nurses’ Health Study and 25,745 men from the Health Professionals Follow-Up Study. The data included detailed information about the participants’ eating habits (collected every four years) and about their lifestyle and health (collected every two years).

The researchers looked first at how the diets of the participants changed over a 12-year period (1986-1998). They then looked to see if there was any association between those changes and the participants’ risk of dying over the next 12 years (1998-2010).

At the start of the study, the participants ranged in age from 35 to 70.

The researchers scored the quality of the participants’ diets by how much they conformed to three different eating plans: the U.S. Department of Agriculture’s Dietary Guidelines for Americans, the Mediterranean Diet, and the Dietary Approaches to Stop Hypertension (DASH) Diet.

Although the particulars of these diets may differ, they share an emphasis on eating more whole grains, vegetables, fruits, nuts and lean proteins (fish and poultry) and consuming less red meat, processed meats, sodium and sugary foods (including sugary beverages).

Key findings

After crunching all the data, Hu and his colleagues found that people who improved their diet-quality scores during the first 12 years of the study were at reduced risk of dying during the subsequent 12 years — no matter which of the three diet scores was used (in other words, no matter which of the three diets their improvements most resembled).

The changes that appeared to be most important to this outcome, however, were those that involved eating more whole grains, fruits, vegetables and fish.

Furthermore, even modest dietary improvements were associated with a decreased risk of premature death. An increase in a diet-quality score of just 20 percent — the equivalent, according to the Harvard researchers, of exchanging just one serving of red or processed meat for one daily serving of nuts or legumes — was associated with an 8 percent to 17 percent reduction in the risk of premature death, depending on which of the three diets was being used for the score.

The longer the improvements were maintained, the lower the risk. People who maintained a higher score for 12 years (as opposed to having their scores drop during that period) were 9 percent to 14 percent less likely to die during the next 12 years.

On the other hand, people whose diets worsened during the study’s initial 12 years, saw their risk of premature death rise by 6 percent to 12 percent.

One further interesting finding: Although dietary improvements were associated with a reduced risk of death in general and of death from cardiovascular disease in particular, such improvements did not result in a reduced risk of death from cancer.

Limitations and applications

This study was observational, which means, of course, that it cannot prove a direct cause-and-effect link between improvements in diet and a reduced risk of premature death.  Other factors may have been involved. Hu and his colleagues did adjust their results for many confounding factors, including age, family history of disease, body mass index, smoking status (and changes in smoking status) and physical activity. But, as the researchers themselves acknowledge, other factors cannot be completely ruled out.

Also, the study’s participants self-reported their dietary and other lifestyle information, and such data can be very unreliable. And they were mostly white health professionals, a factor that makes generalizing the findings to other populations problematic.

Still, as Hu and his colleagues point out in their study, “unhealthy diets have been ranked as a major factor contributing to death and health complications.” Americans need to be making more healthful food choices (and public policies need to be assisting those efforts).

These findings suggest that it’s not the specific diet that’s important as much as its overall components.

“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,” said Hu. “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.”

FMI: The study was published in the New England Journal of Medicine. You’ll find an abstract of the study on that journal’s website, but, unfortunately, the full study is behind a paywall.