Vitamin C (ascorbic acid)

Vitamin C is involved in the synthesis of collagen (skin, blood vessels, bone, cartilage), immune function and the absorption of non-haem iron, and acts as an antioxidant. Sources: citrus fruit, kiwi, peppers, blackcurrants, parsley, acerola.

The original angle (humans, a mutant): a biological curiosity: most animals make their own vitamin C (a goat produces grams of it a day). Humans are among the rare exceptions (with other primates, guinea pigs and some bats) that have lost this gene (GULO, mutated and inactive) over the course of evolution. We therefore depend entirely on food, a rare vulnerability.

This loss goes back ~60 million years; our ancestors had a diet so rich in fruit that the gene became useless, and then broke.

Scurvy, a historic disease: severe deficiency causes scurvy (bleeding gums, fatigue, poor wound healing, tooth loss), the scourge of sailors before the role of citrus fruit was understood. It is one of the first “deficiency diseases” to be identified.

Modern myth-busting:

1. The mega-dose against colds (popularised by Linus Pauling) is overrated: vitamin C does not prevent colds in the general population; it modestly shortens them. Any excess is simply excreted in the urine (“expensive urine”)
2. Cooking and air degrade vitamin C: a freshly squeezed orange juice loses its vitamin C within a few hours in the air
3. Its real practical superpower: multiplying the absorption of plant iron (combine pepper or lemon with lentils)