After years of public health messages promoting healthy eating, most people now know that a poor diet can increase their risk of heart disease, stroke, and type 2 diabetes.
But how much of an effect does diet have on your risk of dying from one of these diseases?
A lot — a new study suggests.
“We combed through studies and data to look at the cumulative effects of poor diet on what we call cardiometabolic diseases — heart disease, stroke, and diabetes — and determined that nearly half of all deaths are linked to poor diet,” Renata Micha, RD, PhD, study author, and research assistant professor at the Friedman School of Nutrition Science and Policy at Tufts University, told Healthline.
In addition, another group of researchers says that fewer overweight and obese people are trying to lose weight, another factor leading to increased risk for heart disease.
Effect of 10 dietary factors
Researchers in the diet study used risk assessment models and national data on dietary habits to determine how many of the more than 700,000 deaths in 2012 from heart disease, stroke, or type 2 diabetes were due to poor diet.
They estimated that 45 percent of the deaths were associated with 10 dietary factors.
Top on the list was excess intake of sodium, which researchers estimated accounted for almost 10 percent of the deaths.
But it’s not just about eating too many foods that are bad for our health.
“Americans are overconsuming salt, processed meats, and sugary-sweetened beverages,” said Micha. “We are underconsuming fruits, vegetables, nuts and seeds, whole grains, vegetable oils, or fish.”
Vegetable oils like those found in soybeans, sunflower seeds, and walnuts are high in polyunsaturated fats, which are known to reduce harmful cholesterol levels.
Fatty fish like salmon, mackerel, herring, and sardines are high in heart-healthy omega-3 fatty acids. Non-fish sources of omega-3s are also available — like flaxseeds, chia seeds, and microalgae — but were not looked at in this study.
In the study, diet accounted for a greater fraction of deaths among African-Americans and Hispanics compared with whites, as well as among adults with low levels of education compared to those with high levels of education.
Researchers also estimated a stronger effect of diet on risk of death in men, which they write is “primarily because of generally unhealthier dietary habits.”
“It’s a wake-up call and another opportunity,” said Micha. “We need to be reminded of this simple truth: eating healthy can and will prevent people from dying prematurely from heart disease, stroke, and diabetes.”
The study was published Mar. 7 in the Journal of the American Medical Association (JAMA).
Positive dietary changes
In a related commentary in JAMA, Noel Mueller, PhD, MPH, and Dr. Lawrence Appel, MPH, caution that the results of the study are from observational research rather than stronger long-term randomized trials, which are difficult to do in nutritional research.
So there is potential that other factors not included in the study may influence the risk of dying. This could include non-dietary factors like income and physical activity levels, or a person’s overall dietary pattern.
“It is possible that processed meat consumption merely reflects a Westernized dietary pattern,” write Mueller and Appel.
They also question whether these 10 dietary factors are the best ones to monitor.
Saturated fat didn’t make the study’s list, but “randomized trials conducted decades ago demonstrated that replacement of saturated fat with polyunsaturated vegetable oil reduced cardiovascular disease events by 18 percent to 41 percent,” write Mueller and Appel.
Saturated fats come mainly from meat and dairy.
In spite of those concerns, Mueller and Appel write that the “likely benefits [of an improved diet] are substantial and justify policies designed to improve diet quality.”
The new study identified a reduction in sodium intake as a prime target for public health policy, something that is already under way.
“The U.S. Food and Drug Administration has recently announced voluntary sodium reduction targets for the food industry,” said Micha. “This is quite timely and we need to engage industry to gradually reduce salt content in processed foods.”
She also points to taxes on sugary beverages passed by U.S. municipalities in recent years as a sign of progress.
In addition, she highlighted promising initiatives like programs in the workplace and schools to promote healthier eating, and improvements in the Supplemental Nutrition Assistance Program for people in the United States with low or no income.
But even without the government’s help, people can take charge of their own health — even if it is one small change at a time.
“Eat more of the good and less of the bad,” said Micha. “Start by making one healthier choice each day and build on it.
Fewer trying to lose weight
Another risk factor for heart disease, stroke, and type 2 diabetes not addressed by the new study is being overweight or obese.
According to the Centers for Disease Control and Prevention (CDC), more than two-thirds of American adults are overweight or obese. And one-fifth of adolescents are obese.
But as overweight and obesity have increased in the United States, fewer people are trying to lose weight, report the authors of a research letter published in the same issue of JAMA.
Researchers used the responses of more than 27,000 adults from the National Health and Nutrition Examination Survey (NHANES) to determine shifts in weight loss over the past few decades.
Overweight and obesity among adults increased during that time — from 53 percent during the period from 1988 to 1994, to 66 percent during the period from 2009 to 2014.
During the same period, the percentage of overweight or obese adults trying to lose weight declined — from 56 percent in 1988 to 1994 to 49 percent in 2009 to 2014.
Study author Dr. Jian Zhang, DrPH, an epidemiologist at Georgia Southern University, and colleagues, write that this “may be due to body weight misperception reducing motivation to engage in weight loss efforts or primary care clinicians not discussing weight issues with patients.”