Protein

Protein is your body's building material. Muscles, skin, hair, organs, hormones, enzymes and immune cells are all made from it. Proteins are made up of amino acids; nine of them can't be produced by the body itself and have to come from food. Unlike fat, there is no real protein store, so you need a fresh supply every day.

How much? The German Nutrition Society (DGE) recommends 0.8 grams per kilogram of body weight a day for adults, and 1.0 gram from the age of 65. At 70 kg, that's around 56 to 70 grams. Children and teenagers need a little more relative to their weight because they're growing – but a balanced family diet covers that easily. If you do a lot of sport or are losing weight, 1.2 to 1.6 grams per kilogram is a good target.

Good sources are pulses, dairy products such as quark, yoghurt and cheese, eggs, fish, lean meat, tofu, nuts and wholegrains. Combining plant and animal sources provides all the amino acids in the best possible balance – potatoes with egg or lentils with rice are classics.

When you're losing weight, protein is your ally: of all the macronutrients, it's the most filling, it protects your muscles while your body breaks down fat, and digesting protein itself uses up part of its energy. A protein-rich breakfast – such as quark with fruit or an egg with wholegrain bread – often keeps you going until lunchtime.

Nobody needs too much of a good thing: protein shakes and bars are unnecessary for healthy children and teenagers, and more than about 2 grams per kilogram brings no benefit for adults either. Real food beats powder.