Mediterranean Diet Limits Deaths Associated with Pollution Exposure

George Thurston, ScD

Eggplant and chickpeas may be putting in more work than previously thought.

A new study has reported that a Mediterranean diet may have preventive measures in people exposed to harmful long-term air pollution, and could even reduce the risk of death from heart attacks and strokes.

The study, presented at the 2018 American Thoracic Society (ATS) International Conference in San Diego, CA, this week, adds to previous findings that suggest dietary changes to add more antioxidants can affect how air pollution exposure affects people, Chris C. Lim, MS, a doctoral student at the New York University (NYU) School of Medicine, said.

“What we did not know was whether diet can influence the association between long-term air pollution exposure and health effects,” Lim said.

Mediterranean foods consist of antioxidant-rich items including fruits, vegetables, whole grains, legumes, olive oils, fish, and poultry. The molecule-heavy diet is favorable to disarming oxidized, highly reactive molecules that are associated with cell and tissue damage.

Lim and his NYU School of Medicine colleagues pulled data from the National Institutes of Health (NIH) American Association of Retired Persons (AARP) Diet and Health Study — which for over 17 years followed 548,699 persons from 6 states — California, Florida, Louisiana, New Jersey, North Carolina, and Pennsylvania — as well as the cities Atlanta and Detroit.

The average person’s age at study enrollment was 62 years old. Over the study’s duration, 126,835 enrolled people had died.

To assess whether adhering to a Mediterranean diet truly changes association between long-term ambient air pollution exposure and cause-specific mortality, researchers conducted a cohort analysis while using annual average exposures to particulate matter (PM_2.5), nitrogen dioxide (NO₂), and ozone (O₃) at the study’s residential locations.

Researchers also utilized the alternative Mediterranean Diet Index (aMED) — a 9-point scale that assesses conformity with the diet, and was constructed per participant from information in cohort baseline dietary questionnaires.

Researchers found Mediterranean diets significantly reduced air pollution-mortality associations for NO₂ with all-cause mortality; PM_2.5 and NO₂ with cardiovascular disease mortality; and PM_2.5 and NO₂ with coronary artery disease mortality (P < 0.05).

In those least adherent to the diet, heart attack deaths increased by 20% for every 10 micrograms per cubic meter increase in PM_2.5 exposure, versus only a 5% increase in those most adherent to the diet.

For every 10 parts per billion increase in NO₂ exposure, heart attack deaths increased by 12% in the least adherent persons — but only 4% in the most adherent persons.

Researchers did not find that Mediterranean diets were protective against long-term exposure to O₃, however — it did no reduce death from all causes, heart attack, or other cardiovascular diseases linked to the pollution-based exposure.

That said, the particular findings are indicative of different avenues for clinical application for successes, and further analysis for failures.

“Given the benefits we found of a diet high in anti-oxidants, our results are consistent with the hypothesis that particle air pollution caused by fossil fuel combustion adversely affects health by inducing oxidative stress and inflammation,” senior study author George Thurston, ScD, director the NYU Program in Exposure Assessment and Human Health Effects, said. “On the other hand, the ozone effect was not significantly blunted by a Mediterranean diet, so ozone apparently affects cardiac health through a different mechanism.”

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