Ginkgo nuts

Eunhaeng is the seed of the ginkgo tree, Ginkgo biloba, a familiar street and temple tree in Korea. The trees flower in April, and the seeds ripen to yellow the following autumn and drop. Each has a soft, foul-smelling outer flesh around a hard white shell, and inside that the edible kernel. It is also called baekgwa (white fruit) and apgakja, "duck's foot," after the shape of the leaves.

Traditionally the seeds were buried in soil for a few days until the outer flesh rotted away, then washed and dried. The kernels are starchy, with some protein and little fat. In Korean cooking they are roasted and eaten on their own, or set as a jewel-like garnish on dishes such as the royal hot pot sinseollo.

Korean and Japanese sources have long warned that eating many ginkgo nuts can cause poisoning. The main toxin is now known to be 4'-O-methylpyridoxine, often called ginkgotoxin, first purified from the seeds in 1985; it interferes with vitamin B6 and can cause vomiting and convulsions.

• A starchy, low-fat nut: Roasted ginkgo nuts are mostly carbohydrate, with some potassium and beta-carotene, per the Korean Food Composition Table.
• Toxic in quantity: Ginkgotoxin depletes active vitamin B6 and can cause vomiting, dizziness and seizures. Most reported cases involve children, but adults have been poisoned too — one case report describes a man with repeated seizures after eating a large amount.
• Cooking does not make them safe: The toxin is heat-stable, so roasted or boiled nuts are still poisonous in excess. Published overdose ranges are wide — from about 7 nuts in children and 40 in adults — so there is no reliable "safe number." Eat only a few at a time and keep them away from young children.
• Handle the fresh fruit with care: The fleshy outer coat is notorious for its smell and is traditionally removed before the shell is cracked.
• Not the same as ginkgo supplements: Ginkgo leaf extracts are a separate product with their own safety profile; nothing here applies to them.