On one bitterly cold day recently James Wong found himself walking home in a light coat. He's an optimist, he explains. But just to make sure he didn't get a cold, when he got home he made his granny's chicken soup, using echinacea root, goji berries and extreme quantities of ginger, chillies and garlic.
“Well, I didn't get a cold,” he says. “It's something I make all the time. In Asia you don't have a big thick dividing line between food and medicine. That soup would be eaten as dinner even if you weren't feeling under the weather.”
Wong's recipe for his Immune System Booster is in his book, Grow Your Own Drugs, a set of instructions for plant-based remedies and beauty products that accompanies the eponymous BBC Two series starting tonight. The title may seem provocative but Wong is an engaging geek (the geek bit is his word) with a mission: he wants people in the West to start looking at plants not as soft furnishings but as chemical factories that are the source of elixirs for everything from insomnia to cystitis and head lice.
Before you dismiss the idea of natural healthcare as flaky, he points out that many plants contain the same active ingredients as over-the-counter drugs. Aspirin, though now synthetic, was originally derived from sal acetic acid which is found in willow, meadowsweet and the shrub spirea. Morphine-based painkillers are based on opium from poppies, and the contraceptive pill was originally isolated from the Mexican wild yam. The World Health Organisation estimates that 80 per cent of the world's population relies on plant-based medicine as its key form of healthcare.