Vitamins

Vitamins are substances your body needs in tiny amounts but can't (or can hardly) produce itself. They don't provide energy but regulate metabolism, immune defence, vision, blood formation and much more. There are 13 vitamins: the fat-soluble vitamins A, D, E and K, and the water-soluble vitamin C and eight B vitamins (including folate – known as folic acid in its synthetic form – and B12).

The body only absorbs fat-soluble vitamins together with a little fat – so a dash of oil in your salad or carrot soup makes sense. They can be stored. The body hardly stores water-soluble vitamins (B12 is the exception); any excess is excreted, so you need a regular supply. Vitamin C and some B vitamins are sensitive to heat and light: cook vegetables gently and don't keep them warm for hours.

Two vitamins deserve special attention. Your skin makes vitamin D using sunlight; from October to March, the sun in Germany usually isn't strong enough for this. For people who don't produce their own, the German Nutrition Society (DGE) gives an estimated value of 20 micrograms a day; babies routinely receive it as drops. Vitamin B12 is found almost exclusively in animal foods – if you're vegan, you need to take a supplement.

Do I need vitamin tablets? For healthy people with a varied diet, usually not. The DGE advises covering your needs through food: fruit and vegetables in different colours, wholegrains, pulses, dairy products, eggs, fish, nuts and oils. When you're losing weight and eating less, this variety is more important than ever. Whether you have a deficiency is something a blood test at the doctor's will tell you – not your gut feeling and not advertising.