Superfoods: Oysters

By | July 01, 2012
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oysters on half shel
Illustration by Maria Schoettler




Prized for their delicate flavor and deep complexity, oysters in all their forms are adored by sea food lovers around the world. For such a small package, the oyster has an astounding range of nutritional benefits, making this humble bivalve one of the planet's most under appreciated superfoods (even for vegetarians).

What is it? True oysters are the edible kind and are distinct from pearl oysters, which are actually saltwater clams and a different family of mollusks. Oysters grow in large beds or reefs, making them essential to the health of many marine habitats. Because they are filter feeders, oysters can be instrumental in removing harmful nitrogen compounds from the environment and converting them into safer byproducts. Ninety-five percent of the world's edible oyster population is sustainably farmed and harvested. Unlike farmed fish and other marine species, oysters eat plankton and do not require wild-caught fish oil or other environmentally damaging supplements to thrive. They are also relatively easy to harvest without damaging the environment, making them a "best choice" on the Monterey Bay Aquarium's Seafood Watch list. In addition to their environmental sustainability, oysters have been considered by some to be an ethical choice for vegetarians because they lack a central nervous system. Every good neuroscientist knows that "pain is in the brain" and not in the body. Though oysters do have a rudimentary nervous system allowing for simple reflexes like snapping shut when disturbed, in an oyster this occurs below the level of consciousness more like the knee-jerk reflex your doctor tests by tapping your knee with a rubber hammer.

Health benefits Another reason for vegetarians to consider enjoying the occasional oyster is that they are incredibly high in vitamin B12, an essential nutrient that is notoriously lacking in vegetarian diets. Just two medium oysters provide over 90% of your recommended daily intake of vitamin B12. Those same two oysters will also provide 170% of your daily zinc requirement. Zinc is essential for the health of human sex organs, and is one of the reasons oysters are often considered an aphrodisiac. Oysters are also extraordinarily high in vitamin D. Sunshine is typically the most abundant source of vitamin D for humans, because very few natural foods contain significant amounts. Pasteurized and homogenized milk has artificial vitamin D added to help reduce the incidence of vitamin D deficiency and childhood rickets. A significant portion of adults are vitamin D deficient, particularly those who live in or north of San Francisco. Like other seafoods, oysters are also an excellent source of complete protein and omega-3 fatty acids. Two oysters also provide 10% of your recommended daily iron, 25% of your daily selenium and only set you back 19 calories. That's pretty impressive.

Health risks Despite their attributes, eating oysters does not come without its risks. Oysters can harbor one of the most deadly bacterial contaminants, known as Vibrio vulnificus, a pathogen considered more deadly than both Salmonella and E. coli. Gulf oysters are particularly vulnerable to contamination during the warmer months of the year, which is why it is commonly said that oysters should only be eaten in months that end in the letter "r." However, this rule of thumb is not true for all oysters. Only oysters that were shucked or cooked alive are safe for human consumption. Live oysters will rapidly snap closed when tapped. If an oyster remains open then it is already dead and should be thrown out. Dead oysters can sometimes be stuck closed, and these make a distinct noise when tapped on the shell. Ask a professional if you cannot tell the difference, and never eat any oyster if you are not sure if it is alive. Alive oysters will open when cooked, and those that remain closed were already dead and should be discarded.

Sourcing In San Francisco, oysters on the half shell are a city tradition. Hog Island Oyster Company located just north of the city in Tomales Bay provides the majority of the Pacific oysters to local restaurants and is a fabulous resource for local oyster enthusiasts. To branch beyond the Pacific, Swan Oyster Depot on Polk is a mecca for oyster lovers. Swan Oyster Depot offers an extensive array of oysters from around the world as well as other fresh seafood. The lines are long, but the oysters are widely considered the best in the city.  


   Superfoods: Oysters, was published in the Winter 2012 issue of Edible San Francisco Magazine. © 2012 Edible San Francisco.

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