Oysters

Food · Animal Foods · Shellfish

Connected to · 2

food source · 2

Zinc
Oysters are among the highest-zinc common foods. Species can differ more than twofold, and cooking concentrates them by driving off water, but even on the conservative figure one serving covers a day's need.
Mechanism · 2
Mechanism · Zinc that holds proteins in shape
A zinc-finger protein has to clamp a zinc ion before it can fold into the shape that grips DNA. The body has no dedicated zinc store; nearly all of its zinc sits in proteins that are at work, so zinc has to come from food every day. The places that need zinc are limited, so eating more does nothing extra for someone who is not short.
Numbers · Enough even on the low figure
Raw eastern oysters have about 39 mg of zinc per 100 g; the Pacific oyster, the species farmed most widely in China, has about 16.6 mg. Cooking concentrates them by driving off water, but the total zinc in each oyster does not change. The US adult Recommended Dietary Allowance (RDA) for zinc is 8–11 mg a day, and a serving of six oysters (about 70–90 g of edible portion) covers or exceeds that even on the conservative figure.
Selenium
One oyster brings zinc, selenium and B12 together. Selenium is built into the active site of antioxidant enzymes, a part those enzymes need in order to work.
Mechanism · 2
Mechanism · One atom at the cutting edge
The body makes selenium into a special amino acid and sets it into the active site of antioxidant enzymes as the cutting edge. Without that edge, the enzyme can fold and still not work. For a nutrient that serves as a part, once enough enzyme has been made, extra has nowhere to go, so the idea that more selenium means more antioxidant power was wrong from the start.
In practice · Selenium in food is not a pill
The selenium in an oyster comes with the whole oyster, in the natural range for food, which is a different thing from swallowing a high-dose supplement. The iron column is often written backwards: Pacific oysters are not low in total iron, but only about 0.85 mg per 100 g is heme iron, so it is absorbed less well than the iron in red meat.

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What oysters are · filter feeders of the sea

EVIDENCEGUIDE 1

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Oysters eat by pumping seawater through their own bodies. That pump lets them store a large amount of zinc in the meat, and zinc's job in your body is to hold a set of proteins in a shape that can work. The same pump also leaves the viruses and bacteria from the seawater in the meat, so eating oysters raw carries a real risk.

An oyster is a bivalve that spends its whole life fixed in one place, filtering the same patch of seawater through its gills again and again. Zinc from the water is kept a little at a time, which makes oysters one of the highest-zinc common foods. Which proteins zinc holds up, and what breaks first when it runs short, is the subject of the later chapter on what zinc does in the body.

If you get fever with chills, feel dizzy or unsteady on your feet, or see painful red patches or blisters on your skin after eating raw shellfish, go to the emergency department right away and tell the doctor you ate raw shellfish. People with liver disease, diabetes, cancer or a weakened immune system are at the highest risk and should not eat them raw.

Oysters go by many names in China: shenghao in Guangdong, hailizi in the north, and haochi once dried. The most widely farmed species in the world is the Pacific oyster, and China is the largest producer, so oysters are not expensive there — they are the high-zinc food ordinary people can most easily get. Eating them raw (with lemon or vinegar) is the mainstream in French and Japanese cooking; grilling over charcoal, steaming, baking with garlic and glass noodles, or frying into an omelet brings the risk down.

Educational content, not medical advice — consult a clinician.

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