Date: 16 Jul 94 10:41:18 GMT From: taltar@beaufort.sfu.ca (Ted Altar) Subject: Complementing Proteins Newsgroups: rec.food.veg Organization: Simon Fraser University Lines: 163 COMBINING PROTEINS The following selection comes from what is still the single best survey of the relevant research regarding nutrition for vegans, VEGAN NUTRITION (1987) by Gill Langley (PhD). Although the terms `first-class' and `second-class' proteins are no longer used, in some circles, the belief persists that a vegan diet, containing only plant proteins, may be inadequate. This is because cereals, nuts and seeds contain less of the amino acid lysine, while being high in methionine; and pulses are rich in lysine but contain less methionine. This has given rise to concern that the amino acid present in lower amounts in each food will limit the availability to the body of the others, and the suggestion has been made (6), and adopted quite widely -- even among vegans -- that complementary protein foods, such as beans and grains, should be eaten at every meal in order to enhance amino acid availability. Vegetarian are also sometimes advised to ensure that they complement vegetable proteins with dairy foods. Are these precautions necessary? Protein combining may reduce the amount of protein required to keep the body in positive protein balance (7), but several human studies have indicated that this is certainly not always the case. For example, over a 60-day period seven human subjects were fed diets in which the protein was derived solely either from beans, corn and refined wheat; beans, rice and refined wheat; or a combination of the plant foods with the addition of cow's milk (8). All subjects remained in positive nitrogen balance (a measure of the adequacy of dietary protein), and there were no significant differences in nitrogen balance between the subjects eating only plant foods and those whose diet was supplemented with milk. Another study looked at the nutritive value of a plant- based diet in which wheat provided 76% of the protein (9). The aim was to determine whether this regime could be improved by adding other sources of plant protein -- such as pinto beans, rice and peanut butter. The diets were entirely vegan, contained only 46g of protein, and were fed to 12 young men over a 60-day period, during which they continued with their normal daily activities. THE RESEARCHERS FOUND THAT ALL SUBJECTS REMAINED IN POSITIVE NITROGEN BALANCE, AND THAT REPLACEMENT OF 20% OF THE WHEAT PROTEIN WITH BEANS, RICE OR PEANUT BUTTER DID NOT RESULT IN SIGNIFICANT CHANGES IN THE LEVELS OF ESSENTIAL AMINO ACIDS IN THE BLOODSTREAM. Even more startling perhaps were the findings of a 59- day investigation with six male subjects who consumed diets win which virtually the sole source of protein was rice (10). At two protein levels (36g and 48g per day) the diets comprised rice as the sole source of protein, or regimes where 15% and 30% of the rice protein was replaced with chicken. The partial replacement of rice with chicken protein did not significantly affect the nitrogen balance of the volunteers (in contrast to earlier experiments with rats which showed that a rice diet did not sustain normal growth). IN THIS *HUMAN* STUDY, EVEN ON THE LOW-PROTEIN DIET, RICE AS THE SOLE SOURCE PROVIDED BETWEEN 2 AND 4.5 TIMES THE WHO-(World Health Organization) RECOMMENDED AMOUNTS OF ALL ESSENTIAL AMINO ACIDS, EXCEPT LYSINE -- OF WHICH IT SUPPLIED 1.5 TIMES THE SUGGESTED LEVEL. On the higher protein diet, rice alone provided between 2 to 6 times the essential amino acid levels suggested by the WHO, and all subjects were in positive nitrogen balance When cornmeal was fed as virtually the sole source of protein to ten male volunteers during a 100-day study it was found that at an intake of 6g of nitrogen per day (approx. 36g protein) not all the subjects were in positive nitrogen balance (11). Yet all the essential amino acids were eaten in amounts which met or exceeded standard requirements, with the exception of tryptophan 00 of which 91% was provided. THESE RESULTS SUGGEST THAT ON A CORN-PROTEIN DIET, NON-SPECIFIC NITROGEN IS THE FIRST LIMITING FACTOR, NOT LACK OF ESSENTIAL AMINO ACIDS. The 1988 Position Paper Of The American Dietetic Association (12) emphasized that, because amino acids obtained from food can combine with amino acids made in the body, it is not necessary to combine protein foods at each meal. Adequate amounts of amino acids will be obtained if a varied vegan diet -- containing unrefined grains, legumes, seeds, nuts and vegetables -- is eaten on a daily basis. THESE AND OTHER SIMILAR EXPERIMENTS SHOW CLEARLY THAT DIETS BASED SOLELY ON PLANT SOURCES OF PROTEIN CAN BE QUITE ADEQUATE AND SUPPLY THE RECOMMENDED AMOUNTS OF ALL ESSENTIAL AMINO ACIDS FOR ADULTS, EVEN WHEN A SINGLE PLANT FOOD, SUCH AS RICE, IS VIRTUALLY THE ONLY SOURCE OF PROTEIN. THE AMERICAN DIETETIC ASSOCIATION EMPHASIZES THAT PROTEIN COMBINING AT EACH MEAL IS UNNECESSARY, AS LONG AS A RANGE OF PROTEIN RICH FOODS IS EATEN DURING THE DAY. (6) "Diet for a Small Planet", 1976. (7) J. PHYSIOL. CHEM., 1970, 351:1485. (8) AM. J. CLIN. NUTR., 1973, 26:702. (9) AM. J. CLIN. NUTR., 1971, 24:181. (10) AM. J. CLIN. NUTR., 1971, 24:318. (11) J. NUTR., 1965, 86:350. (12) J. AM. DIET. ASSN., 1988, 88:352. Indeed, varied sources of proteins need not be eaten at each meal, but even 12 hours apart, as the absorbed amino acids are temporary stored continue be complemented during meals taken later in the day. Gill Langley's book is also very useful for lacto- vegetarians as well, since many of the same issues and nutritional needs of vegans apply to all vegetarians. Also, the comparison between vegans and lacto-vegetarians is useful information for all vegetarians. Really, this book is a must for every vegetarian who wishes to get informed about vegetarian nutrition and have plenty of references to primary sources to further research or peruse on one's own. You can buy copies from: The Vegan Society Ltd 7 Battle Road St Leonards-on-Sea East Sussex TN37 7AA A more comprehensive vegetarian mail-order house has recently been established by PAWS (The Progressive Animal Welfare Society). They actually have a store in Seattle: The PAWS Store 8503 Greenwood Ave. N. Seattle, WA 98103 U.S.A. Phone/Fax (206) 782-1700 Write and ask for their extensive catalogue of vegetarian books and pro-animal book, vegetarian vitamins, vegetarian sandals, etc. Alternatively, you can also mail-order for a copy of Gill :Langley's book from the following pro-vegetarian organization that is also worth supporting: THE AMERICAN VEGAN SOCIETY 501 OLD HARDING HIGHWAY MALAGA, NJ 08328 U.S.A. Phone: (609) 694-2887 Hope this helps, Ted Altar