glycemic index (GI) — a measure of how quickly a carbohydrate-rich food increases your blood sugar concentration. Pure glucose, which dissolves rapidly into the blood, is used as a reference, with a GI of 100. Low GI foods, which release glucose slowly, include apple juice and pasta.
HDL (high-density lipoprotein) — see cholesterol
insulin — a hormone produced by the pancreas, and released into the blood when the concentration of blood sugar rises after a meal. It causes cells to absorb glucose.
kilocalorie (kcal) — see calorie
LDL (low-density lipoprotein) — see cholesterol
macronutrient — any of the three most important families of substance in food; carbohydrates, fats and proteins.
metabolic rate — the rate at which the body uses energy, usually expressed as kilocalories per day.
micronutrient — any important chemical compound in foods that is not a carbohydrate, fat, protein, water or fiber. Vitamins, minerals and antioxidants are examples of micronutrients.
mineral — chemical element essential in our diets (except carbon, hydrogen, nitrogen and oxygen, which are found in abundance in all foods). Most dietary minerals are metals; examples include iron and calcium.
monosaturated fat — a type of unsaturated fat founds in some foods, including mayonnaise, sunflower oil and oily fish, and generally regarded as a healthy type of fat. Omega-3 and omega-6 fatty acids are polyunsaturated fats.
protein — one of the macronutrients (along with carbohydrates and fats). Digestive enzymes break down proteins into smaller molecules called amino acids. Inside your body's cells, amino acids join together to make new protein molecules. Proteins make up about half the dry weight of every cell in your body; enzymes are proteins, and hair and nails are almost pure protein.
saturated fat — a type of fat found commonly in meat, cheese and butter, and generally regarded as unhealthy in large quantities. The consumption of high levels of saturated fat is associated with heart disease.
starch — a carbohydrate common in many foods, including bread, rice and potatoes. It breaks down easily to form glucose. Plants make starch as a way of storing glucose - it is the plant equivalent of glycogen.
trans fats — a type of fat normally made by reacting vegetable oil with hydrogen (they are then called partially hydrogenated vegetable oils). Trans fats are soft, and ideal for baking, and they do not spoil as quickly as vegetable oils. They are found in fast foods and confectionery, although they are becoming less common, because they are the least healthy type of fat. Trans fat in your diet increases your risk of developing heart disease.
unsaturated fat — a type of fat that is most often found in fish and vegetables, and is regarded as healthier than saturated fats.
vitamin — a micronutrient essential to the human body, and found in food (in particular, in fruits and vegetables). Some vitamins are antioxidants, others take part in important chemical reactions. A deficiency of each vitamin causes disease; for example, if you do not eat enough vitamin C, you will develop a disease called scurvy; lack of vitamin D can lead to rickets.
