by Craig Weatherby
An intriguing study from Mexico City suggests that people in the world’s dirtiest cities should be taking fish oil... or eating as much fatty fish as they can.
People in many crowded cities are exposed to high levels of particulate pollutants from vehicle exhaust and industrial emissions.
These tiny particles can harm the heart, possibly by introducing free radicals that cause “oxidative stress”… the process whereby unstable oxygen compounds steal electrons from surrounding molecules, wreaking havoc in our cells.
Earlier trial shows heart protection from fish fats
Four years ago, researchers from the Mexican National Institute of Public Health, led by French researcher Isabelle Romieu, M.D., conducted a clinical trial that tested nutritional approaches to mitigating pollution damage.
(If Dr. Romieu's name sounds familiar, it's because we published two prior reports by her, regarding the effects of omega-3s in asthma and heart health (see “Mothers’ Fish Oil Intake May Reduce Kids’ Asthma Risk”).
Dr. Romieu’s team tested the ability of fish oil and soy oil to prevent the undesirable impacts on heart rate variability associated with exposure to particulate matter smaller than 2.5 micrometers—tiny pollutants called PM2.5.
They observed no benefit in people taking supplemental soybean oil, which contains small, naturally occurring percentages of short-chain omega-3s.
But the Mexican scientists saw substantial improvements in people taking fish oil, which is naturally rich in the long-chain “marine” omega-3s (EPA and DHA) essential to cellular metabolism and a healthy immune system.
As they wrote then, “Supplementation with 2 grams a day of fish oil prevented heart rate variability decline related to PM2.5 exposure in the study population” (Romieu I et al. 2005).
Last year, these same researchers published the results of their effort to test the indirect antioxidant effects of fish oil and soybean oil in a similarly situated group of nursing home residents.
New Mexican study finds antioxidant boost from fish oil
The same team set out to see whether fish or soy oil supplements might also prevent the reductions in protective antioxidant enzymes in the body associated with exposure to PM 2.5 pollutants.
The key antioxidant enzymes in question were copper/zinc superoxide dismutase (Cu/Zn SOD), manganese SOD, and glutathione peroxidase (GSH-Px).
Dr. Romieu and her co-workers recruited 52 elderly nursing home residents—average age 76.5—for a seven-month study.
An initial three-month stage with no supplements was followed by four months of receiving either fish oil or soy oil supplements.
Each participant in this randomized, double-blind, controlled trial took two gram doses of one of the two oils.
The fish oil capsules were naturally rich in long-chain omega-3s (called EPA and DHA).
In contrast, soy oil contains very small amounts of the short-chain plant-form omega-3 fat called ALA, from which the body makes long-chain omega-3s.
Analysis of blood samples taken before and during supplementation showed that consumption of either fish or soy oil was associated with lower levels of oxidative damage in blood cells.
However, far greater benefits were seen in the fish oil group:
- Activity of the volunteers’ Cu/Zn SOD antioxidant enzymes activity increased by 49 percent in the fish oil group, but only by 23 percent in the soy oil group.
- Levels of GSH antioxidant enzymes increased by 62 percent in the fish oil group, and by 55 percent in the soy oil group.
- Soy oil produced no effect on levels of lipo-peroxidation (LPO) products - a marker for oxidative stress - while the fish oil group enjoyed a 72.5 percent decrease in LPO products.
Next time you travel to a smoggy city, take along some fish oil!
- Romieu I, Garcia-Esteban R, Sunyer J, Rios C, Alcaraz-Zubeldia M, Velasco SR, Holguin F. The effect of supplementation with omega-3 polyunsaturated fatty acids on markers of oxidative stress in elderly exposed to PM(2.5). Environ Health Perspect. 2008 Sep;116(9):1237-42.
- Romieu I, Téllez-Rojo MM, Lazo M, Manzano-Patiño A, Cortez-Lugo M, Julien P, Bélanger MC, Hernandez-Avila M, Holguin F. Omega-3 fatty acid prevents heart rate variability reductions associated with particulate matter. Am J Respir Crit Care Med. 2005 Dec 15;172(12):1534-40. Epub 2005 Oct 6.