On Monday, researchers from the University of Washington (UW) debuted a new tool in Nature Medicine, which uses a five-star rating system to help users identify diet and lifestyle changes that are supported by evidence, Isabella Cueto writes for STAT. 

New tool identifies evidence-backed diet and lifestyle changes

To create the tool, researchers at UW's Institute for Health Metrics and Evaluation (IHME) analyzed hundreds of studies to help consumers, clinicians, and policymakers—who are constantly met with conflicting information from food lobbyists and influencers—understand the scientific consensus behind diet and lifestyle changes.

The researchers are calling the tool the "Burden of Proof Studies," largely because the research must prove whether a practice is legitimate. "Burden of Proof allows us to understand better how the risk actually changes with consumption," the authors said.

In the medical field, "there's always been some skepticism" about how behavioral changes can impact a person's long-term health, especially when those changes relate to specific foods or activities, said Christopher Murray, senior author of the papers and founder of the IHME.

However, Jeffrey Stanaway, assistant professor of global health and lead author on the group's analysis of vegetable health studies noted that "[d]iet research is really challenging."

"It is difficult for researchers to measure how much people eat, to do so over time, and to separate their diet from other health factors (people who eat lots of fruits and vegetables are more likely to exercise, for example)," Cueto writes.

Still, research suggests that changes in diet and other behaviors play an important role in disease prevention. Roughly half of the U.S. population currently has a chronic condition, and long-term illnesses—including heart disease, diabetes, and cancer—are major contributors to disability and death around the world.

"The vast majority of what makes you healthy happens outside the doctor's office," said Georges Benjamin, executive director of the American Public Health Association. 

The link between common diet and lifestyle changes and health outcomes

Most dietary habits received a rating between one and three stars, signaling a need for more robust research. "I was very surprised at how many of the diet-risk relationships were much weaker" than expected, Murray said. 

Among the relationships rated by the tool, the relationship between fibrous vegetable consumption and ischemic stroke was the strongest, with three stars. According to the data, an increase in vegetable consumption from one to four daily servings led to around a 23% reduction in stroke risk. For heart disease, the analysis showed a two-star rating between the disease and vegetable consumption.

"The evidence on vegetables is pretty good," Stanaway concluded.

However, the study did not evaluate starchy vegetables, including potatoes, sweet potatoes, and corn. It also excluded cured and pickled vegetables like kimchee and sauerkraut. 

"Even a conservative interpretation of the evidence, which the IHME tool uses, showed eating more vegetables is tied to a reduced risk of chronic disease, though future studies could affect that," Cueto writes. According to the researchers, the tool will need to be updated as more research becomes available.

Notably, the evidence on red meat's links to disease were weak—a finding Benjamin, who was not involved in the research, said was not surprising. "The things that have always been kind of fuzzy still look kind of fuzzy," he said. 

According to the researchers, the strongest ratings for a meat-heavy diet were two stars, which were linked to colon and rectum cancer, breast cancer, ischemic heart disease, and type 2 diabetes.

Researchers also found that a diet high in red meat could provide some protection against strokes—evidence that earned a one-star rating. "[A] large, well-designed study on people with diets high in red meat could make a big impact," Cueto writes.

The tool also found that across eight health outcomes, including larynx cancer, aortic aneurysm, peripheral arterial disease of the lower limbs, tracheal, bronchus and lung cancer, and chronic obstructive pulmonary disease, were strongly linked to tobacco use.

"It is irrefutable that tobacco is a major risk to health and really has a broad set of impacts across multiple cardiovascular and cancer outcomes," Murray said. 

However, the link between smoking and several other illnesses, including ischemic heart disease, esophageal cancer, stroke, type 2 diabetes, was not as strong. Notably, researchers found a one-star link between smoking and asthma—a finding the researchers did not expect.

How the tool could be useful

According to the IHME team, findings of low ratings should be viewed as areas for research investment.

It will take time for clinicians, policymakers, and patients to appreciate the value this tool can bring, Benjamin said. "[T]he data alone might not be enough to sway the public's understanding of risk," Cueto writes.

"Where the rating system could be useful in the long run is the doctor's office, when a clinician is crafting a care plan for a patient with multiple risk factors," she adds. 

If our knowledge about those risks can be compared, then doctors and patients might be able to get a better sense of what to prioritize, Benjamin noted. "The less things you give people to do, the better, and the more likely they are to comply," he added. (Cueto, STAT, 10/10)