22 June 2005

The Problem With Fish

Because fish can be healthful as well as hazardous, medical experts have grappled for years with what advice to give people, particularly pregnant women, about how much is safe to eat.

A new study by Harvard University doctors concludes that pregnant women can boost their baby's intelligence by eating fish a couple of times a week, but only if they avoid varieties with large concentrations of mercury.

Fish is full of omega-3 fatty acids, which help young brains develop and seem to protect against heart disease. But it also is tainted by mercury, a potent neurotoxin that interferes with the building of brains.

The new study of 135 Boston-area babies is considered important because it quantifies and compares the risks and benefits of a fish diet.

The researchers concluded that pregnant women should eat fish because their babies are likely to score higher on intelligence tests. But they also reported that the benefits of the nutrients disappear and the babies' intelligence scores drop substantially if the fish contains high levels of mercury.

[LATimes - Jun 20, 2005]

In the said study, the highest intelligence scores came from babies whose mothers had consumed more than 2 servings of fish per week but whose mercury levels remained under 1.2 parts per million (ppm).

Fish is healthy because it has omega-3 fatty acids which are good not only for the heart, but also for improving intelligence. The problem is mercury, which is both poisonous and has a high-affinity for fish and other seafood products.

Methymercury toxicity can produce a variety of symptoms but the most prominent are sensory disturbances in the extremities, visual field problems, impaired hearing and equilibrium. It is also sometimes called Minamata Disease, after the 1956 mercury poisoning in Minamata Bay in Kumamoto Prefecture, Japan.

According to a study by Narvaez in 2002, there are 2 sources of mercury pollution in the Philippines: "mined mercury deposits and use of mercury in gold extraction in at least 20 provinces in the country." Her study is an eye-opener, and I encourage you to read it in full if you have time.

The best option is to follow the revised US FDA's guidelines which recommend that pregnant and nursing mothers (also those planning to become pregnant) eat up to 2 meals, or 12 ounces, of fish weekly. Children are advised to heed the same guidelines because their brains are still developing.

Other useful links:
Seafood Contamination Myths vs. Facts
2003 Global Mercury Assessment
What You Need to Know About Mercury in Fish and Shellfish

6 reactions:

Toni said...

In more concrete terms...

Is it therefore safe to eat those Century canned tunas? In moderation I suppose?

Dr. Emer said...

That's right, Toni. All in moderation.

Tin said...

i was about to ask about canned fish like tuna and sardines. at least safe pa rin basta in moderation.

thanks, doc!

bayi said...

There is no doubt about the value of fish oil but cunsumption in moderation seems to be the safest thing to do.

R. O. said...

Doc, what about the other heavy metals?

Dr. Emer said...

Good question, master XP. The other heavy metals can also cause contamination and poisoning, but mercury is particularly notorious for its affinity with fish. Other heavy metals like lead, arsenic, cadmium, and many others are also harmful but you usually get from other sources like contaminated drinking water, air pollution, and unintentional occupational exposure.

Here are some helpful links you might find interesting:

Heavy Metals

Mercury Poisoning and Heavy Metal Toxicity