The folk wisdom that fish is a remarkable food has been confirmed by scientists who have found that omega-3 fatty acids in fish oil lower ‘bad’ cholesterol levels and lessen the risk of cardiovascular disease. Recent studies suggest that fish consumption can also improve eye and brain development, help avert macular degeneration and adult-onset diabetes and alleviate rheumatoid arthritis, Parkinson’s disease and even some mental illnesses.
The American Heart Association promotes eating fish at least twice a week.
But some fish, particularly larger, long-lived species, contain mercury, a powerful neurotoxin that can inflict severe damage on the developing brain and nervous system. Mercury-contaminated fish poses particular dangers to pregnant women, women of childbearing age, infants and young children.
Which fish are likely to contain the most omega-3s and the least mercury? The federal Food and Drug Administration and Environmental Protection Agency offer only sketchy guidance.
But eating fish doesn’t have to be a roll of the dice. To help consumers make more informed choices, Gary L. Ginsberg and Brian F. Toal, scientists with the Connecticut state Department of Public Health and authors of the book What’s Toxic — What’s Not, have come up with a detailed risk/benefit analysis of popular food fish, species by species. 
In a study published in the February 2009 edition of Environmental Health Perspectives, the influential journal of the National Institute of Environmental Health Sciences, Ginsberg and Toal lay out their calculations in painstaking detail.
And, for consumers who just want to know which types of fish will give them the biggest health benefit with the least mercury content, there’s a speed-read:
For best neurodevelopmental results:
- Unlimited — Tilapia, pollack, flounder, shrimp, trout, herring, salmon
- Twice per week — Canned light tuna, cod
- Once per week — Canned white tuna, tuna steak, halibut, sea bass, lobster
- Do not eat — Swordfish, shark
For best cardiovascular benefits:
- Unlimited — Tilapia, pollack, flounder, shrimp, trout, herring, salmon, canned light tuna, cod
- Twice per week — Canned white tuna, halibut, sea bass, lobster
- Once per week — Tuna steak
- Do not eat — Swordfish, shark
With one caveat: the advice to eat ‘unlimited’ quantities of tilapia, pollack, flounder, shrimp, trout, herring and salmon ‘may need to be tempered for certain fish (e.g., farm-raised salmon) because of other contaminants and end points (e.g., cancer risk).’
Ginsberg and Toal also warn that more research needs to be done on the impact of varying doses of both omega-3s and mercury, particularly concerning how mercury exposure may affect the cardiovascular system.
Although there is still much to be learned, the Ginsberg-Toal study’s well-researched, soundly-reasoned and essentially positive message is a must-read for those who want straight facts and smart analysis.
”
(Via Enviroblog.)