·NUTRITION· • ENERGY AND PROTEIN .

According to the Department of Health's Dietary Reference Values for Food, Energy and Nutrients in the United Kingdom, published in 1991, estimated average daily needs forenergyand protein are as follows:

These, however, are only average needs, which means that many people will require more. To be sure ofobtaining enough protein, recommended amounts for the 18-49 age group are: boys and men, 55 g; girls and women, 45 g.

Proteins, which are necessary for the growth, maintenance and healing of body tissues, are composed of amino acids in different proportions and arrangements. The proportions in animal proteins are similar to man's and therefore said to have a high biological value, while those in plants are different and said to have a lowvalue: to raise it, you need to eat more than one kind at roughly the same time. Soya is exceptional in having a high value and is thus of especial importance to vegans.

A point about protein which should perhaps be stressed is that even if you eat the recommended amount and are careful about combining plant proteins, you will not utilise it for its longer-term purposes ifyou run yourself short of calories, since it will be burnt up instead of fats or carbohydrates for energy.

Besides protein you need 12 different vitamins, a large number of minerals (but most of them in minute quantities) and fibre. Anyone who eats a variety of fresh (or frozen) and some wholegrain foods will almost certainly obtain more than enough of all of them, but recommended daily amounts for men and women aged 19-49 of the main vitamins plus calcium, iron and sodium are given below, with brief comments on their functions. For foods containing them, see the table on page 184.

• VITAMIN A.

Promotes healthy skin, hair and eyes. Men need 700 JLg; women, 600 JLg.

• B VITAMINS.

The B group of vitamins is needed to metabolise various constituents of food. Bl is required for carbohydrate; B2 for protein, fat and carbohydrate; B3 to maintain levels of sugar and cholesterol in the blood. B12 is needed to metabolise some amino acids and by the nervous system: lack leads to a certain type of anaemia and to permanent neurological damage. The chief sources of it are animal foods, such as milk and eggs, but some bacteria and hence fermented products, like miso and yeast extract, which are permissible for vegans, also contain it.

• VITAMIN B1 (THIAMIN).

Men need I mg; women, 0.9 mg.

• VITAMIN B2 (RIBOFLAVIN).

Men need 1.3 mg; women, 1.1 mg.

• VITAMIN B3 (NIACIN).

Men need 16.5 mg; women, 13 mg.

• VITAMIN B12.

Men and women need 1.5 JLg.

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VITAMIN C.

Promotes healing; prevents scurvy. Men and women need 40 mg.

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VITAMIN D.

Maintains levels of phosphorus and potassium in the blood. The most important source is sunlight; if you lead a normal life and are outside reasonably often, you do not need further supplies via food.

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Needed to form bones and teeth. Men need 1,000 mg; women, 800 mg.

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IRON .

Needed for the formation of red blood cells which carry oxygen around the body; lack leads to anaemia. Men need 8.7 mg; women (because of having to compensate for that lost in menstruation) 14.8 mg.

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SODIUM AND CHLORINE.

Sodium chloride = salt; needed to maintain water balance and for nerve and muscle function. Exertion involving much sweating raises the amount needed: otherwise, both men and women need about 3 g.

Fibre is obtained from plant cellulose, a good source of which is husks and bran, one reason for preferring whole to refined foods.

However, you are recommended to avoid excessive amounts, so that to use white rice or flour for some purposes is not deleterious.

Sugar which occurs naturally as part of foods such as fruit does not harm the teeth; added sugar (both brown and white) and honey does.

- CHOLESTEROL-

For most people, cholesterol in food is not a major factor in blood cholesterol: more important is the amount of saturated fat eaten. You are advised not to eat more than 30% of your total calorie intake in the form offat and not more than 10%, i.e. about 200 kcal, in the form of saturated fat. The chiefsources of saturated fat in a vegetarian diet are oil and butter, cream and cheese. Double cream, for instance, contains 30 g per 100 g;