Healthy Skepticism Library item: 2686

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Publication type: news

Gerstel J.
Trolling for truth in fish debate
Toronto Star 2005 Oct 21
http://www.thestar.com/NASApp/cs/ContentServer?pagename=thestar/Layout/Article_Type1&c=Article&cid=1129845011301&call_pageid=991479973472&col=991929131147

Notes:

Ralph Faggotter’s Comments:
This amusing article highlights the dilemas which the average person ( and even an expert) faces when having to make decisions about health issues.
Here we are dealing whih whether or not to eat fish, but it gets even more complicated and difficult to decide in relation to some medications.

Full text:

Trolling for truth in fish debate

JUDY GERSTEL
STAFF REPORTER

You’re sitting at an upscale restaurant and your appetite says, “Go fish.”

Fortunately, in a fancy font on the menu is a fine selection of fresh fish: salmon, tuna, tilapia, pickerel.

But wait! Isn’t it dangerous to eat fish – or at least some kinds of fish? Is tilapia safer than tuna? Or is it the other way around? And if the salmon is farm-raised, is it better or worse than if it’s wild …

Isn’t also true that fish is supposed to be really good for you, full of Omega-3 fatty acids that help prevent coronary heart disease, stroke and maybe even dementia?

Fish isn’t just a good meal anymore. It’s a great big fat (and fatty acid) dilemma.

The dilemma is addressed in papers in this week’s American Journal of Preventive Medicine. The issue’s theme is Fish: Balancing Health Risks and Benefits.

Much of the message is about the harms and benefits of public health policies and interventions to manipulate fish consumption.

“Overall consequences could be adverse if fish consumption is reduced in the general population, which has apparently occurred,” warns epidemiologist Dr. Walter Willet, chair of the nutrition department at the Harvard School of Public Health.

He slams a “widely publicized report in a prominent journal” about farmed salmon containing measurable amounts of organochloride compounds.

“That publication likely caused substantial numbers of premature deaths,” he states provocatively, because it “almost certainly contributed to a reduction in fish consumption.”

He calls the publication “perhaps even irresponsible – because the implied health consequences were based on hypothetical calculations and very small.”

In contrast, he writes, “the benefits of eating salmon based on human data at the doses actually consumed … are likely to be at least 100-fold greater than the estimates of harm, which may not exist at all.”

The risk/benefit analysis comes in a paper coauthored by Joshua Cohen, senior research associate at the Harvard Center for Risk Analysis.

“For consumers, the message is pretty straightforward if you’re an adult and not going to become pregnant,” says Cohen, speaking by phone from Cambridge, Mass.

“You should eat fish. Mercury is not an issue.”

Cohen has a Ph.D. in Decision Sciences from Harvard University. His specialty is the analysis of uncertainty – which makes him handy to have around whenever you’re weighing pros and cons, especially if, like me, you can say, “Quandaries R Us.”

But unless you’re pregnant or about to become pregnant, eating fish, says Cohen, does not have to be one of those quandaries.

“For all practical purposes, you don’t need to worry about it.”

The problem with mercury, he explains, is that it’s a neurotoxin.

“That sounds really bad but in the grand scheme of things, the effects of mercury at the levels we’re talking about are pretty subtle.

“However, when you’re dealing with the developing nervous system of an unborn child, or very young child, something even that subtle can have an important effect.”

Pretty straightforward stuff until you remember a report last week in this Health section about a study showing that pregnant women should eat fish.

Explains Cohen, “The Omega 3 fatty acids in fish are important for the developing brain (of the fetus).”

His advice, after weighing all known risks and benefits?

“The best evidence available suggests that pregnant women should eat fish low in mercury,” advises Cohen. “Light canned tuna, for example. Part of the confusion is that white canned tuna has moderate mercury levels.”

But Cohen and his cohorts also look at the big picture beyond individual consumers weighing options at the fish counter.

For example, more fish consumption which could lead to a healthier population may also, in the long term, have a negative impact.

That’s because catches of wild fish are near maximum and the fish farming needed to meet increased demands has potentially negative consequences for the environment and therefore, eventually, for human health.

Also, warns a companion paper in the journal, encouraging people to eat only fish with the lowest mercury content “may well channel the consumption of less desirable, possibly toxic, fish toward poorer and less-informed populations, including perhaps women of childbearing age in developing countries.”

In other words, fish becomes not just a menu or supermarket dilemma but also a socioeconomic issue. Market forces, driven by the choices of people who are better informed, are likely to increase the consumption of less desirable fish by the poor, the population most vulnerable to any diminution of IQ points, suggest Australian epidemiologists who coauthored the paper.

The bottom line, says Cohen, is that people who make decisions about issuing advisories and altering fish consumption need to get a better handle on all the risks and benefits and implications.

“It’s like throwing a stone in a pond,” he says, using an apt metaphor for a fishy issue. “There are ripples, secondary and tertiary.”

One of the ripples from Cohen’s research is that he will have to eat more fish.

“I do not actually like fish much,” he admits. “But my wife, based on my study – the only time anything I’ve done at work influenced my wife – she went out and found these inexpensive salmon burgers and we’re going to break those out.”

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jgerstel@thestar.ca