Ocean Watch

Monday, September 23, 1996

Ancient Jewish command on
shellfish makes sense

Today is Yom Kippur, the most important holiday in Judaism. Some people fast on this day to atone for their sins.

This fasting practice got me wondering about other Jewish food restrictions, shellfish in particular. I called a Jewish friend.

"Why don't Jews eat shellfish?" I asked.

"Shellfish are scavengers," he said. "It's healthier not to eat them."

"Was it a health issue when it started?"

My friend wasn't sure, so he referred me to Rabbi Avi Magid of Temple Emanu-el.

"It's more a philosophy than a health issue," Rabbi Magid told me. "Jews have a maxim: You are what you eat - and that was long before Frank Zappa was around. So we don't eat animals that prey on other animals, either dead or alive. That includes shellfish and fish without scales."

"Is there a Bible passage about this?"

"Yes. Leviticus 11, verses 9-12: "These you may eat of all that are in the water: whatever ... has fins and scales... that you may eat. But in all the seas or in the rivers that do not have fins and scales... they are an abomination to you... you shall not eat their flesh."

This ancient command makes sense. I once traveled to a remote seaside village in the Philippines with Vernon Ansdell, a Hawaii physician who specializes in tropical medicine.

We had just been served steaming platters of enormous red shrimp, which I piled high on my plate.

Vernon leaned close to my ear as I was peeling my first shrimp. "Those are filter feeders," he whispered.

"What?" I said.

"Consider where we are," he said. "They don't have sewage treatment plants in these villages." His plate held only rice and cooked greens.

I couldn't gracefully return my shrimp to the serving plate, and I had trouble choking them down. It was the last time I ate shellfish in a developing country.

What diseases can you get from eating these scavengers? It depends, of course, on what's in the water the animals are filtering and how thoroughly they are cooked during preparation. Heat kills most viruses and bacteria, but some shellfish are savored raw or undercooked.

Hepatitis is one notorious illness that can accumulate in shellfish growing in areas where untreated sewage gets into the ocean.

This was the disease Vernon was most worried about during our Philippines trip, where we were served shellfish at nearly every meal.

Clams and oysters sometimes carry diseases closer to home.

On both U.S. coasts, entire shellfish beds are sometimes closed to harvesting due to red tide, a flood of toxin-bearing marine organisms. Red tides cause shellfish poisoning when people eat contaminated bivalves. Cooking does not destroy this toxin.

Vibrio, a brand of bacteria that live naturally in warm seawater, can also get into oysters, crabs and other shellfish.

People in California and Florida have died from Vibrio vulnificus infections after eating raw oysters. (Vibrio is killed with thorough cooking.) All the infected oysters came from restaurants or markets.

In Japan, where people eat large amounts of raw seafood, Vibrio parahaemolyticus is a common cause of food-borne diarrheal illness.

This infection is rarely diagnosed in the United States. However, in 1972, Hawaii experienced a significant outbreak. Thirty-one people suffered diarrhea after eating raw crabs infected with Vibrio parahaemolyticus. All survived.

Shunning shellfish may be a fundamental religious principle for Jews, but sometimes, it's also a healthy choice.