VegSocUK Information Sheet THE VEGETARIAN SOCIETY ___________________________________ PROTEIN Being vegetarian does not mean your diet will be lacking in protein. Most plant foods contain protein and in fact it would be very difficult to design a vegetarian diet that is short on protein. Excess dietary protein may lead to health problems. It it now thought that one of the benefits of a vegetarian diet is that it contains adequate but not excessive protein. Proteins are made up of smaller units called amino acids. There are about 20 different amino acids, eight of which must be present in the diet. These are the essential amino acids. Unlike animal proteins, plant proteins may not contain all the essential amino acids in the necessary proportions. However, a varied vegetarian diet means a mixture of proteins are consumed, the amino acids in one protein compensating for the deficiencies of another. STRUCTURE & FUNCTIONS Proteins are highly complex molecules comprised of linked amino acids. Amino acids are simple compounds containing carbon, hydrogen, oxygen, nitrogen and occasionally sulphur. There are about 20 different amino acids commonly found in plant and animal proteins. Amino acids link together to form chains called peptides. A typical protein may contain 500 or more amino acids. Each protein has it's own unique number and sequence of amino acids which determines it's particular structure and function. Proteins are broken down into their constituent amino acids during digestion which are then absorbed and used to make new proteins in the body. Certain amino acids can be made by the human body. However, the essential amino acids cannot be made and so they must be supplied in the diet. The eight essential amino acids required by humans are: leucine, isoleucine, valine, threonine, methionine, phenylalanine, tryptophan, and lysine. For children, histidine is also considered to be an essential amino acid. Proteins are essential for growth and repair. They play a crucial role in virtually all biological processes in the body. All enzymes are proteins and are vital for the body's metabolism. Muscle contraction, immune protection, and the transmission of nerve impulses are all dependent on proteins. Proteins in skin and bone provide structural support. Many hormones are proteins. Protein can also provide a source of energy. Generally the body uses carbohydrate and fat for energy but when there is excess dietary protein or inadequate dietary fat and carbohydrate, protein is used. Excess protein may also be converted to fat and stored. DIETARY SOURCES Most foods contain at least some protein. Good sources of protein for vegetarians include nuts and seeds, pulses, soya products (tofu, soya milk and TVP), cereals (wheat, oats, and rice), free-range eggs and some dairy products (milk, cheese and yoghurt). Different foods contain different proteins, each with their own unique amino acid composition. The proportions of essential amino acids in foods may differ from the proportions needed by the body to make proteins. The proportion of each of the essential amino acids in foods containing protein determines the quality of that protein. Dietary proteins with all the essential amino acids in the proportions required by the body are said to be a high quality protein. If the protein is low in one or more of the essential amino acids the protein is of a lower quality. The amino acid that is in shortest supply is called the limiting amino acid. Protein quality is usually defined according to the amino acid pattern of egg protein, which is regarded as the ideal. As such, it is not surprising that animal proteins, such as meat, milk and cheese tend to be of a higher protein quality than plant proteins. This is why plant proteins are sometimes referred to as low quality proteins. Many plant proteins are low in one of the essential amino acids. For instance, grains tend to be short of lysine whilst pulses are short of methionine. This does not mean that vegetarians or vegans go short on essential amino acids. Combining plant proteins, such as a grain with a pulse, leads to a high quality protein which is just as good, and in some cases better, than protein from animal foods. Soya is a high quality protein on its own which can be regarded as equal to meat protein. The limiting amino acid tends to be different in different proteins. This means when two different foods are combined, the amino acids in one protein can compensate for the one lacking in the other. This is known as protein complementing. Vegetarians and vegans eating a well-balanced diet based on grains, pulses, seeds, nuts and vegetables will be consuming a mixture of proteins that complement one another naturally without requiring any planning. Beans on toast, cheese or peanut butter sandwich, muesli with milk (soya or cow's), and rice with peas or beans are all common examples of protein complementing. Previously, it has been thought that protein complementing needed to occur within a single meal. However, it is now known that this is not necessary as the body keeps a short-term store of the essential amino acids. A well-balanced vegetarian or vegan will easily supply all the protein and essential amino acids needed by the body. Good sources of protein (single servings) Chick peas (200 g or 7 oz) 16.0 g Baked beans (225 g or 8 oz) 11.5 g Tofu (140 g or 5 oz) 10.3 g Cow's milk (1/2 pint) 9.2 g Lentils (120 g or 4 1/4 oz) 9.1 g Soya milk (1/2 pint) 8.2 g Muesli (60 g or 2 1/4 oz) 7.7 g Egg, boiled 7.5 g Peanuts (30 g or 1 oz) 7.3 g Bread, (2 slices) 7.0 g Hard cheese (30 g or 1 oz) 6.8 g Fair Sources Brown rice (200 g or 7 oz) 4.4 g Porridge [water] (160g or 6oz) 2.4 g Potatoes (200g or 7 oz) 2.8 g Broccoli (100g or 3 1/2 oz) 3.1 g Poor sources 1 Apple 0.3 g 1 Carrot 0.4 g Cream, double (20 g or 2/3 oz) 0.3 g Butter or margarine (7g or 1/4oz) None Vegetable oil None Sugar or syrup None REQUIRED INTAKES The old Recommended Daily Amounts (RDA's) have now been replaced by the term Reference Nutrient Intake (RNI). The RNI is the amount of nutrient which is enough for at least 97% of the population. Research has shown that we do not need as much protein as previously thought. The recommended amounts of protein for adults and children has more than halved in the last 20 years. Reference Nutrient Intakes for Protein, g/day. Age RNI 0 to 3 months 12.5 g 4 to 6 months 12.7 g 7 to 9 months 13.7 g 10 to 12 months 14.9 g 1 to 3 yrs 14.5 g 4 to 6 yrs 19.7 g 7 to 10 yrs 28.3 g Men 11 to 14 yrs 42.1 g Men 15 to 18 yrs 55.2 g Men 19 to 49 yrs 55.5 g Men 50 + yrs 53.3 g Women 11 to 14 yrs 41.2 g Women 15 to 18 yrs 45.4 g Women 19 to 49 yrs 45.0 g Women 50 + yrs 46.5 g Pregnant women 51.0 g Breast feeding women 53 to 56 g Increased protein needs during pregnancy and breast feeding are usually met simply by the extra calories from more food. Because infants and children are growing they require more protein than adults (proportional to their body weight). Children on a balanced diet usually get enough protein as long as they are getting enough energy (or calories). RNI values for protein are valid only if energy needs are also met. If energy needs are not met then dietary protein is used for energy rather than tissue growth and repair. This is not generally of concern to vegetarians as plant sources of protein tend to also be a good source of carbohydrate, used for energy. Contrary to popular belief athletes and those who engage in a lot of exercise do not necessarily need extra protein as the extra energy required for strenous activity is best supplied by carbohydrates. The extra protein needs of a body builder can usually be supplied by an increased energy intake from more food. Whilst vegetarian diets usually meet or exceed protein requirements, they are typically lower in total intake of protein than non-vegetarian diets. This lower protein intake may well be beneficial as high protein intake has been associated with osteoporosis and aggravating poor or failing kidney functioning. It is recommended that protein intake should not exceed twice the RNI. MEAL PLAN Sample one day's meal plan to meet the RNI of 45g for an adult women. Breakfast Museli (60g or 2oz) 7.7 g Milk (1/4 pint) 4.6 g Lunch Two slices of toast (80 g or 2 2/3 oz) 7.0 g Baked beans (225 g or 8 oz) 11.5 g Evening meal Brown rice (200g or 7oz) 4.4 g Tofu (140g or 5oz) 10.3 g Vegetables Fruit TOTAL PROTEIN INTAKE 45.5 g An extra two slices of bread and , pint of milk gives 11.6 g protein and would easily reach male requirements of 55.5 g/day. ___________________________________ // This article is copyright to the Vegetarian Society (UK), but may be freely copied for non-commercial use provided it is kept intact, not altered and these lines are included. For futher information contact: The Vegetarian Society, Parkdale, Dunham Road, Altrincham, Cheshire WA14 4QG, England. Tel: (England) 061 928 0793 email: vegsoc@vegsoc.demon.co.uk // [The text of this file was obtained from the Vegetarian Society (UK) in March 1995.]