Coffee and tea reduce exposure to mercury when eating fish: Université de Montréal study

By Karen Seidman, Gazette Universities Reporter

The Gazette

November 9, 2011

U de M study, showed that boiling and frying tuna, shark and 

mackerel reduced exposure to mercury by about 40 to 60 per cent, 

while coffee and tea ingested at the same time as raw fish reduced exposure 

by about 50 to 60 per cent. The two combined pretty much eliminated 

exposure to mercury. Photograph by: Max Rossi, Reuters

MONTREAL - Forget saki – a groundbreaking new study from the Université de Montréal shows that sushi-lovers should be eating their raw fish with coffee or tea to reduce their exposure to mercury.

The study, published last week in the journal Environmental Research, also shows that boiling or frying fish significantly reduces exposure to mercury.

And having cooked fish with a cup of coffee or tea – 250 millilitres – reduces the exposure to mercury to almost nothing, according to the results of the study, which shocked even the researchers working on it.

“The magnitude of the effect was surprising,” said Marc Amyot, a professor of biological sciences at U de M and one of the lead researchers on the study.

“We thought there might be a five- to 10-per-cent reduction (in the exposure to mercury). We don’t usually see such dramatic results.”

The study, conducted using in vitro techniques simulating human digestion, showed that boiling and frying tuna, shark and mackerel reduced exposure to mercury by about 40 to 60 per cent, while coffee and tea ingested at the same time as raw fish reduced exposure by about 50 to 60 per cent.

The two combined pretty much eliminated exposure to mercury.

Amyot cautioned more study is needed, but the findings could be good news for fish lovers who enjoy the benefits of fish as a lean protein but worry about the mercury found in it.

Mercury – found in highest amounts in fish like shark and red tuna – can cause adverse neurological effects, is a possible carcinogen and has even been found to have cardiovascular effects on humans.

Pregnant women in particular have been told to stay away from it as consumption of fish is considered the main form of ingestion-related mercury exposure.

Researchers also studied whether corn starch reduced exposure to mercury and found it had only a weak effect.

The benefits of cooking the fish hadn’t previously been known; for example, an article in Scientifc American in 2008 says it doesn’t matter if you eat tuna raw or cooked – mercury levels will be the same.

Now we know cooking may reduce the exposure to mercury.

“This is what you call a provocative study,” Amyot said. “It opens the door to more research.”

He said he wouldn’t want anyone to interpret the findings to mean that it’s healthier to eat fried fish and chips than sushi.

“It’s important to balance the benefits of eating raw fish that isn’t full of oil,” he said.

The most famous case of mercury poisoning was a few years ago when actor Jeremy Piven, best known as Ari Gold on HBO’s Entourage, bowed out of David Mamet’s Broadway play Speed the Plow, blaming high levels of mercury from too much sushi.

Mamet famously skewered Piven’s departure by saying: “My understanding is that he is leaving show business to pursue a career as a thermometer.”

Amyot also plans to study the effects of alcohol on mercury exposure from eating fish.

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kseidman@montrealgazette.com

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