Vitamins & minerals

You eat carbohydrates, protein, and fat in grams, often several hundred grams a day. Vitamins and minerals, by contrast, are needed only in milligrams, and iodine only in micrograms. A milligram is a thousandth of a gram, a microgram another thousandth of that. These tiny amounts supply no energy: no vitamin and no mineral has calories. Yet nothing works without them, because they are the tools and spare parts inside the body. If one of them is missing, you often notice it only after weeks, but then all the more clearly.

Vitamins: 13 helpers from your food

Vitamins are delicate substances that your body can almost never make on its own. They have to come with your food. There are 13 of them in total, and they fall into two groups. Four are fat soluble: A, D, E, and K. The body puts them into store in the liver and in fat tissue, and it only takes them up well when there is some fat in the meal, a spoon of oil on the carrots for example. The other nine are water soluble: vitamin C and the eight B vitamins. They are hardly stored at all, and whatever is left over leaves the body with the urine. That is why you need a fresh supply of them almost every day. An adult needs around 100 milligrams of vitamin C a day, and half a bell pepper already contains that much.

Every vitamin has its own building site. Vitamin C is needed for collagen, the glue in skin, gums, and connective tissue. Vitamin A sits in the visual pigment of your eyes and makes seeing at dusk possible, and your body builds it from the orange colouring in a carrot. Vitamin D is the great exception among the vitamins: your skin makes it itself as soon as enough sunlight falls on it. It makes sure the gut takes up calcium from your food so that bones stay hard. From October to March, though, the Sun stands so low in central Europe that the skin barely produces any vitamin D. The body then lives off the reserves it built in summer.

Minerals come out of the ground

Minerals are not delicate compounds but plain chemical elements: calcium, magnesium, sodium, potassium, iron, iodine, and a few more. They originally come from rock and soil. Plants draw them up with water through their roots, and through vegetables, grain, and animals they end up on your plate. Of some your body needs a lot: about 1000 milligrams of calcium a day, which makes bones and teeth hard and is found in milk, yoghurt, cheese, broccoli, and some mineral water. Of others mere traces are enough: 10 to 15 milligrams of iron, and only around 200 micrograms of iodine a day. Iron sits in the red blood pigment haemoglobin and binds the oxygen there, the thyroid gland needs iodine for its hormones, and sodium and potassium let nerve cells pass their signals on. One difference from vitamins matters: minerals are indestructible, heat does nothing to them. But they can move into the cooking water and be poured away with it.

Too little and too much

An old seafaring story shows just how much depends on these tiny amounts. On voyages lasting months there was only hard biscuit and salted meat, no fresh fruit or vegetables. Sailors' gums bled, teeth fell out, and old wounds opened up again. The illness is called scurvy and comes purely from missing vitamin C, because without collagen the body cannot hold its connective tissue together. In 1747 the ship's surgeon James Lind tried several remedies side by side on board, and only the group given oranges and lemons recovered. Other shortages still follow the same pattern today: too little iron makes you tired and pale, too little iodine makes the thyroid swell, which is why table salt is usually enriched with iodine. Too much can do harm as well. Water soluble vitamins are simply flushed out, while fat soluble ones build up. High dose tablets of vitamin A or vitamin D can therefore become dangerous, whereas ordinary food practically never delivers them in excess.