From Trout to Tilapia—Which Fish Is Best?

Healthnotes Newswire (July 17, 2008)—Everyone knows that fish is good for you, but it turns out that some is better than others for certain health needs and goals.

A new study, published in the Journal of the American Dietetic Association, analyzed 30 species of wild and farmed fish and found that while wild fish is generally more healthful than farm-grown, fish such as salmon and trout still maintain a beneficial fatty acid profile. Other farmed fish, such as talapia, do not, so while these may be incorporated into a regular diet as an occasional inexpensive, low-fat protein source, people wanting to maximize disease-fighting health benefits from fish will opt in favor of those with a better balance of fatty acids.

The ratio is the real measure of risk

A wealth of research shows that eating fish rich in omega-3 fatty acids may help prevent and treat diseases such as heart disease, diabetes, inflammatory and autoimmune diseases, and some cancers. However evidence increasingly points to the ratio of omega-3 to the less discussed omega-6 fatty acids in the diet as the indicator of disease risk.

• Fish with an omega-3 to omega-6 ratio of greater than one are considered beneficial because of their effect on the fatty acid profile of the entire diet.

• Fish with a ratio of 0.5 or lower are considered not protective against disease.

As a polyunsaturated fat, omega-6 also plays a role in supporting health, as long as it is consumed in moderation.

The best fish for fending off disease

The authors of the study collected samples of commonly eaten fish—including tuna, snapper, mahi-mahi, cod, sole, halibut, haddock, talapia, swordfish, catfish, salmon, and trout—from distributors in the US and Chile, from fish farms in the US, Chile, Canada, Ecuador, Honduras, Norway, and New Zealand, and from supermarkets in the US. Some highlights of their findings include:

• Sockeye salmon, Coho salmon, Copper River salmon, and farmed rainbow trout had a beneficial fatty acid pattern—in other words, a high ratio of omega-3 to omega-6 fatty acids.

• Farm-raised Atlantic salmon had high levels of omega-3 fatty acids but their levels of omega-6 fatty acids were higher than those of the wild salmon, making their ratio slightly less favorable, though still healthy.

• Tuna, one of the most commonly eaten fish in the US, had a low level of omega-3 fatty acids, but it also had a low omega-6 level, so its ratio remained favorable.

• On the other end of the spectrum, farmed talapia and catfish had low levels of omega-3 and poor ratios of omega-3 to omega-6 fatty acids.

Balancing factors besides fatty acids also important

Of all the fish reviewed in this study, tilapia has received the most attention for its unfavorable fatty acid content. “All other nutritional content aside, the inflammatory potential of hamburger and pork bacon is lower than the average serving of farmed tilapia,” the article cautions. However, keep in mind that a fish not being highly protective against heart disease does not mean it needs to be avoided entirely. Other health factors, such as heavy metal contamination—which are high in otherwise healthful fatty fish like tuna, but low in less heart-healthy fish like tilapia—should also be taken into account.

To give the pros and cons of fish consumption some real world perpective, consider that eating moderate amounts of farmed tilapia is roughly equivalent to other staples of the average diet, and may be a reasonable option for some people. For those at risk for inflammatory diseases such as heart disease, fish with a good omega-3 to -6 ratio such as salmon or trout are the best choice.

(J Am Diet Assoc 2008;108:1178–85)