Five healthy college women, 19 to 25 years old, were fed 4 isonitrogeneous mixed plant protein diets in which whole wheat flour (WF); three varieties of sorghum Purdue normal (PN) ; high lysine (HLY) ; and Nigeria normal (NN) and navy bean flour (B) , in various blends, provided 6.7g nitrogen (N) plus 0.8g N from low N foods daily for 24 days. Mean daily calcium (Ca) balances were +147, + 158, +25O, and +I88 mg/day, respectively. Ca balances of subjects fed diet containing navy beans (WF: PN: B, 50: 30: 20) were higher than for those fed the other diets. However, this may be due to higher lysine intake provided by the mixture.
Diet I1WF:HLY (50: 50)” produced the lowest phosphorus balance due to high fecal excretion of the mineral. The mixture containing (70%) WF had higher magnesium (Mg) content and induced more positive Mg balance during the experimental period. The diet containing 50% sorghum and 50% wheat produced the lowest iron balance, however, this might be attributed to higher phytate content of the diet. The mixture containing 70% WF induced higher niacin levels in the subjects. this may be due to higher dietary intake.
The mean balances produced by the diets are higher than the normal range reported for this compound. The subjects fed “WF: HLY: PN (25: 25: 50)” diet had negative riboflavin balance. On the other hand, the same diet had higher folic acid content and induced higher balances of the nutrient in subjects fed the diet.
Sorghum is the second most important feed grain grown in the United States. It ranks third after rice and wheat as a cereal
1 This study was supported by SEAICooperative Research grant for human consumption in Asia and is second only to maize in Africa(1). Wheat is of great importance in developing countries as a major source of calories, protein, vitamins, and minerals. The importance of these two cereals in human nutrition enhances the need for additional information on the metabolic utilization of nutrients supplied by these grains and their products.
The utilization of vitamins and minerals in sorghum and wheat by human adults are scanty. Klinc(2) reported the excretion of thiamin by adult subjects maintained on diets consisting entirely of wheat breads in 2 to 4-day tests. Guillemet et al. (3) evaluated the thiamin excretion of four subjects who ingested wheat breads of 100, 85. and 758 extraction. Edwards and her associates (4) reported that thiamin was well utilized whether supplied by diets containing wheat or animal protein in male adults. Studies in man and animals showed the problems in mineral metabolism due to consumption of large quantities of wheat and sorghum.
The absorption of calcium, phosphorus, and iron was reported to be decreased by the phytate of whole wheat or sorghum (5,6) . However, in flours of 70 to 80% extraction the major portion of this component is removed (6,7). The rachitogenic effect (7,8) and the cariogenic nature (9) of high wheat diets have been attributed to the low content of calcium and the disproportionate amount of calcium compared with phosphorus. Recently, reports indicate a relationship of the protein quality of wheat-containing diets to this cariogenic effect (10,ll) , involving specifically its low lysine content. The influence of lysine on the absorption of calcium has now been well documented (12, 15) .
The current study is part of a larger study, the objectives of which were to determine the adequacy of diets containing sorghum, wheat, and bean proteins for human adults. This report presents the results of excretion of vitamins (niacin, riboflavin, vitamin Be and folic acid) and minerals (calcium, magnesium, iron and phosphorus) . A previous paper has presented data on the metabolism of nitrogen and the excretion of urinary 3-methylhistidine (16) in female adults fed these diets.
MATERIALS AND METHODS
Five normal healthy female university students were investigated. They were fully informed about the purpose of the investigation and the studies to be made. During the study, subjects carried on their usual activities except for the consumption of the experimental diets and the collection of metabolic materials for 24 days. The subjects signed written informed-consent forms, and the experimental protocol was approved by the Virginia State University Committee on the use
of humans as experimental subjects. The composition of the test diets was described elsewhere(l6). Four blends of whole wheat flour (WF) , high lysine sorghum (HLY); Purdue normal sorghum (PN); Nigeria normal sorghum (NN) and navy beans (B) were formulated.
The amounts of essential amino acids contributed by major protein sources were considered in planning the blends to allow mutual supplementation. ‘GW provided 70-25% of the 6.7g. nitrogen (N) in the diets depending on t’he blend. Table 2 (16); HLY furnished 20% of the total N. Low N foods (apples, peaches, peas, carrot, tomato soup, grapefruit juice, chocolate cookie, rusk bread, and high calorie beverage drinks) purchased from (General Mills Chemicals Minneapolis, MN
55425) were added to the diets daily to increase calories and introduce variety.
The total N intake was raised to 7.5g from all N sources. The dietary components were made into baked products, weighed, sliced into three equal parts and served among all meals. The experimental design, sex, age, weight, and height of the subjects were reported previously (16). Urine and feces were collected for 24 hr periods during the last 3 days of each 6 days period. Urine was collected in hydrochloric acid, feces were collected in suitable plastic containers. Urine, feces, and foods were analyzed for vitamin and mineral content by various methods. Feces collected in each of the 24 hr periods were mixed, dried in an air oven, weighed,
ground in mortar, and portions analyzed in duplicate for vitamins and minerals.
Food riboflavin and niacin were determined by the A .O .A.C. procedure (26). Urinary riboflavin was estimated by Morel1 and Slater method (27). while urinary folic acid was estimated as described by Melnick and Field (28). Vitamin B6 content of foods and urine were determined by the method of Srivastava and Beutler (29)
and folic acid by the method of Akluwalia and Kuczala(30). Calcium, iron, magnesium, and phosphorus content of the foods were estimated by the A .O.A .C. method (26). the urinary and fecal content of these materials were determined by the method of Willis (31) .
Analysis of variance and the Duncan multiple range test were applied as described by Steel and Torrie (32).
RESULTS AND DISCUSSION
The urinary excretion of calcium is shown in Table 1. Calcium (Ca) balances of subjects fed various mixed plant protein diets (Table 1) were +147, +158, +250 and +I88 mg/day, respectively. Based on current reports of a beneficial effect of lysine on the absorption of calcium (12-15) it is possible that the higher Ca balance bserved when participants were fed diet containing navy bean may suggest the higher lysine intake provided by this mixed protein diet (16). it might as well be due to its higher Ca content. The urinary Ca values of subjects fed “WF:NN:HLY (70: 15: 15)” diet (Table 1) Vere greater than those of subjects fed other three diets, and the corresponding Ca balances for these women were less positive except for those fed diet containing navy beans.
Many have reported on Ca excretion by human adults, (Adolph and Chem(l7) Kunerth and Pittman (18) NIcCance et al. (19) Basu and Basak (20) , and by children, (Panemangolore et al. (21), who were fed diets primarily based on wheat. Walker et al. (22) and IVIcCance and Walsham(23) reported negative Ca balances when self-selected diets of human subjects were changed to those containing lower quantities of Ca suppiied by wheat bread alone. Our experiments differ slightly from those above in that our diets contained less wheat.
Part of the dietary Ca were provided by sorghum and navy beans. Our experiments also differ from that of Edwards et al. (4) in that no Ca supplement was provided to bring dietary intakes of this nutrient to recommended level.
The levels of urinary and fecal phosphorus (P) of the subjects are presented in Table 1. The subjects fed WF:HLY (50: 50) diet had lowest P balance. The reason for his low balance was due to a high fecal excretion of P.
The excretion of magnesium (Mg) in urine of the subjects is shown in Table 1. The mean Mg balances for the subjects were +515.5. +640, +935, and +850mg daily for the four diets, respectively. Diet “WF: NN: HLY (70: 15: 15) supplied more Mg than the other rations, and this appears b be the reason the subjects who were fed this diet had more positive balances during the experimental period. The role of fiIg in physiologic processes is now more clearly shown, therefore, the relationships of Rilg to the metabolism of specific essential and nonessential amino acids, calcium, and complex carbohydrate needs more detail study.
Table 1 presents iron (Fe) balances of subjects fed various mixed plant protein diets. The subjects given the ration that contained 50/50%, whole wheat and sorghum proteins, respectively, had the lowest Fe balance. McCance et al. (24) observed that addition of sodium phytate to white bread decreased Fe absorption and they attributed the lower Fe balences of persons consuming brown bread to its higher phytate. Sharpe et a1 (25) observed in adolescent boys that addition of sodium phytate to milk (0.2 in 200ml) decreased Fe absorption 15-fold. In this study, the lower Fe balances of the subjects fed diet “WF:HLY (50: 50: ) ” might be attributed to higher phytate content of the diet. The higher Fe balances of the subjects fed “WF: PN: B (50: