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Boiled turnip with rock candy is the standard Persian home remedy for a winter cough.

It soothes a sore throat. There's no trial showing it shortens an infection, and honesty matters here.

One cup cooked carries around 2 g of fibre and a third of the day's vitamin C.

Shalgham is a cold-weather root. Once cooked, it's mild and faintly sweet. Raw, it's sharp and mustardy. In Iran, it belongs to winter in a way few vegetables belong to a season. From November, street vendors sell it hot in paper cups, and every household has an opinion about how long to simmer it. No one can trace how old the remedy is, but it survives because a hot, sweet, soft root genuinely soothes a raw throat.

Known to botanists as Brassica rapa.