Mediterranean Diet Can Offset Harms of Breathing Polluted Air, Study Finds

Eating a Mediterranean diet can offset some effects of living in areas with polluted air, according to a 17-year study involving more than 540,000 people, which was unveiled Monday the American Thoracic Society 2018 International Conference in San Diego, California.

Consuming fruits, vegetables, whole grains, olive oil, fish, and legumes—instead of red meat and processed foods—gives the body antioxidants that offset inflammation caused by breathing fine particulate matter and nitrous oxide. The more people stuck with the diet, the authors found, the greater the benefits.

However, study author George Thurston, ScD, director of the Program in Exposure Assessment and Human Health Effects at the Department of Environmental Medicine, NYU School of Medicine, said that while the study’s results confirmed the hypothesis that particle air pollution caused by fossil fuel combustion adversely affects health by inducing oxidative stress and inflammation, the same was not true for ozone, suggesting that cardiac effects are caused by a different mechanism.

“We found that the effect of pollution also has to do with the mechanism air pollution,” Thurston said in an interview with The American Journal of Managed Care®.

Although Thurston said more work is needed to confirm these results, the effects of inflammation on the body have been well-studied over the past decade, particularly among researchers probing the mechanisms of diabetes and obesity. Inflammation, which causes insulin resistance and is the main cause of type 2 diabetes, wreaks havoc on the body across a range of conditions—from rheumatoid arthritis to psoriasis to depression. In the interview, Thurston said it’s been documented that people with chronic diseases are more susceptible to the effects of air pollution. People with diabetes and rheumatoid arthritis are also known to be adversely affected by cigarette smoke, which also deposits particulate matter and causes oxidative stress.

Size of the study sets it apart

The study is not the first to examine these links. “Previous studies have shown that dietary changes, particularly the addition of antioxidants, can blunt the adverse effects of exposure to high levels of air pollution over short time periods,” Chris C. Lim, MS, a doctoral student at the NYU School of Medicine, said in a statement. “What we did not know was whether diet can influence the association between long-term air pollution exposure and health effects.”

But the size of the cohort, which was drawn from data from the National Institutes of Health-AARP Diet and Health study, offered researchers the ability to examine this question over a very extended period, across a large population. That study followed 548,699 people, average age 62, from 6 states—California, North Carolina, New Jersey, Florida, Louisiana, Pennsylvania—as well as the cities of Atlanta and Detroit. Over that period, 126,835 people in the study died. Researchers identified 5 groups of participants based on level of adherence to the Mediterranean diet and their level of exposure to particulate matter, nitrous oxide, and ozone, using census tract information.

Researchers measured how closely participants followed the Mediterranean diet using the alternative Mediterranean Diet Index (aMED), a measure that uses a 9-point scale to assess conformity with the diet. The scale constructed per participant from information in cohort baseline dietary questionnaires.

They found:

• Deaths from cardiovascular disease (CVD) increased by 17% for every 10 micrograms per cubic meter (µg/m³) increase in long-term average PM₅ exposure in those least adherent, compared to 5% among the most adherent.
• CVD deaths increased by 10% for every 10 parts-per-billion in nitrous oxide exposure in those least adherent to the diet, compared to 2% among those who were most adherent.
• Deaths from heart attacks rose 20% for every 10 µg/m³ increase in particulate exposure in those least adherent to the diet, compared to 5% among the most adherent.
• Heart attack deaths increased by 12% for every single part-per-billion increase in nitrous oxide exposure in those least adherent, compared to 4% among the most adherent.
• Deaths from all causes increased by 5% for every 10 parts-per-billion increase in long-term average nitrous oxide exposure in those who were least adherent to the diet, compared with the 2% most adherent to the diet.

Thurston said the study demonstrates the importance of 2 things: focusing on efforts to control pollution, but also educating the public on what people can to minimize its effects. “You want to optimize both,” he said. “You want to have the public choose the healthiest pathway and the ways that will help them resist the effects of pollution, not just focus on defense,” through healthy diets, “but also on controlling the problem by going after the most dangerous sources of pollution—which appear to be the fossil fuels.”

Reference

Lim CC, Hayes R, Ahn J, Shao Y, Thurston GD. Air pollution, Mediterranean diet, and cause-specific mortality risk in the NIH-AARP diet and health study. Presented at the 2018 American Thoracic Society International Conference; San Diego, California; May 18-23, 2018; Abstract 17198.