Dephytinized bran

Two metabolic balance studies were conducted using healthy adult men to study the effect of phytate on bioavailability of dietary calcium. Dietary treatments were each 15 days in duration. In the first study, a mean daily calcium balance of 208+58 (SD) mg was observed when 2.0 g of phytate from 36 g of whole wheat bran was consumed daily with 1100 mg of calcium, phytate/calcium molar ratio 0.11. Calcium balance was 184+87 mg when 36 g of dephytinized bran was consumed with the same intake of calcium, phytate/calcium molar ratio 0.01. In the second study, calcium intake was 740 mg/day. 

Two metabolic balance studies conducted in our laboratory have yielded information relative to the effect of phytate and dietary fiber on calcium bioavailabilty. In the first study, a relatively high intake of dietary fiber was consumed with a 10-fold difference in phytate intake from wheat bran. In the second study three levels of phytate were consumed with a low amount of dephytinized bran as the principal dietary fiber source. The two higher phytate levels in the latter study were attained using sodium phytate. 

The diet treatments were level of phytate intake, either 0.2 or 2.0 g/day. Each level was consumed for 15 days, three consecutive repeats of the 5-day menu cycle. To provide 2.0 g/day of phytic acid, 36 g of wheat bran was baked into 6 muffins and two muffins were eaten each meal. Dephytinized bran was prepared by incubating the bran in water and allowing the endogenous phytase to hydrolyze the phytate, then the entire incubation mixture was freeze-dried (4) and 36 g baked into 6 muffins. Thus, the intake of all nutrients and neutral detergent fiber was the same for both phytate intakes. Five subjects consumed the whole bran muffins for 15 days followed by the dephytinized bran muffins for 15 days and the other 5 subjects in the reverse order. Brilliant blue dye was given at breakfast on the first day of each collection period to aid in demarcation of stools. Stool composites were made for days 1-5, 6-15, 16-20 and 21-30 and urine composites for days 6-15, and 21-30. Daily food composites were made, homogenized, freeze-dried and then analyzed to determine mineral nutrient intakes. 

Component1 Whole Bran Muffins Dephytinize Bran Muffins... 

Our studies do not resolve the question of phytate vs fiber for the effect of wheat bran on dietary calcium bioavailability. Phytate level clearly affected apparent absorption of calcium in HS-II in the presence of an amount of the water insoluble fraction of dephytinized bran equivalent to 12 g of untreated bran and the phytate supplied as sodium phytate. An additional trial using untreated bran and the same amount of fiber as the water insoluble fraction with sodium phytate could resolve the question of fiber vs phytate. In HS-I, the balances were positive when a relatively large amount of bran, 36 g/day, was consumed. Calcium intakes were possibly higher than most men consume, but under the dietary conditions imposed for 15 days, the phytate and fiber of 36 g of bran did not express an adverse effect on calcium balance. 

Possible future studies include chemical characterization of the fiber components of the dephytinized bran and the water insoluble fraction and in vitro binding studies using whole bran and the fractions (18). 

Simpson et al. (24) did not observe increased non-heme iron absorption when dephytinzed bran was included in a test meal compared to the non-dephytinized bran. Removal of phytic acid from soy protein likewise did not improve non-heme absorption (38). Decreased iron balances, observed by Bodwell et al. (40) with soy isolate diets, did not appear to be associated with the level of phytic acid a tendency for zinc balances to decrease with increased phytic acid was observed. 

The effect on zinc balance of a 10-fold difference in dietary molar ratio of phytate/zinc was tested in a metabolic balance study with 10 adult men. The mean zinc balance was 2.7 mg per day vrtien the dietary molar ratio of phytate/zinc was about 12 and 2.0 mg per day when the ratio was about 1. Menus consisted of foods commonly consumed in the United States. The mean daily intake of zinc was 17 mg and of neutral detergent fiber 16 g. The molar ratios of phytate/zinc were attained by using 36 g per day of whole or dephytinized wheat bran. Analysis of hospital and self-chosen diets Indicate that the majority of the United States population consume diets with molar ratios of phytate/zinc less than 10, but which provide less than the recommended dietary allowance of zinc. The balance results are discussed in relation to magnitude of the zinc intake, the type of food consumed and the role of adaptive responses in maintaining adequate zinc nutriture. 

Nutrient intake. Table II summarizes the daily intakes of zinc and phytic acid. The range of zinc intake is the result of the different caloric levels consumed. About one-third of the zinc consumed was contained in the muffins. About 95% of the phytic acid was derived from the muffins and, since the same number of muffins was eaten regardless of caloric level, there was no difference due to the caloric level in phytic acid intakes. There was, however, a ten-fold difference in phytic acid intakes by type of bran muffin. The mean calculated molar ratio of phytate/zinc was about 12 when whole bran muffins were consumed and just greater than 1 when dephytinized bran muffins were... 

Key solid symbols, whole bran and open symbols, dephytinized bran. 

Whole bran muffins, (-) dephytinized bran muffins. 

Mean + S.D., Fasting blood sample morning of day indicated. 2(+)Whole bran muffins preceding 15 days, (-) dephytinized bran muffins preceeding 15 days. a,b,c Significantly different, P < 0.05. 

The dephytinized bran contained the same percentage of neutral detergent fiber as the nonincubated whole bran. Thus, the intakes of neutral detergent fiber did not differ between the two dietary... 

Monoferric phytate is the major fraction of iron in wheat bran, and is a highly bioavailable form of dietary iron in contrast to insoluble di- or tetra-ferric phytate. Monoferric phytate equilibrates with the miscible nonheme iron pool of a meal in extrinsic label iron absorption tests. Whole wheat bran depressed absorption by humans of nonheme iron in a meal. Dephytinized wheat bran also inhibited nonheme iron absorption by humans and the inhibition could not be clearly attributed to either the insoluble or soluble fractions of the dephytinized bran. Adult men who consumed 36 g of wheat bran per day had positive iron balances. Iron balance was not increased when dephytinized bran was consumed. The form of ferric phytate must be known to properly explain the effect of phytic acid on iron absorption. The overall meal composition must be considered to evaluate the effect of wheat bran on iron nutrition of humans. 

Table IV presents the RBV for the iron of three breakfast cereals not fortified with iron. The two ready-to-eat cereals were sources of highly bioavailable iron, but the instant cereal was significantly lower in bioavailability than the reference salt. We have not studied the chemical nature of iron in commercially available wheat based foods. The iron that remains in the residue of 1.2 M ammonium acetate extracted wheat bran was only 71 as bioavailable as the extracted monoferric phytate (6j, but the iron of enzymatically dephytinized wheat bran, which may be complexed with amino acids, is highly bioavailable (11).

Table V. Dephytinized Wheat Bran and Absorption of Nonheme Dietary Iron by Humans ...

No Bran (A) Untreated Bran (B) Lyophlized Bran2 (C) Dephytinized Bran 3 (D)... 

Table VI. Effect of Soluble and Insoluble Fractions of Dephytin-ized Wheat Bran on Absorption of Dietary Nonheme Iron by Humans 1...

Meals consisted of milkshake with 100 mg ascorbic acid and 2 muffins, bran muffins contained 12 g dephytinized bran or equivalent per meal. Eighteen subjects. 

We conducted a metabolic balance study, in conjunction with the Human Study Facility at Beltsville, to compare mineral balance of humans consuming whole bran or dephytinized bran continuously over several weeks. Results of this study have been published in part (17. 18. 19), and the results for iron will be summarized here. Ten adult men consumed menus that... 

Each meal included two-bran muffins that contained 6 g each of either whole bran or dephytinized bran (36 g of bran consumed each day). The bran was milled from a single lot of hard red spring wheat and one-half was dephytinized by action of the endogenous phytase. The mean iron intake was 18.2 mg per day, approximately one-third in the muffins. Phytic acid intakes were 2.0 and 0.2 g per day, respectively, when whole bran muffins or dephytinized bran muffins were consumed, but there was no difference in neutral detergent fiber intakes, 17 g per day. 

Each type of bran muffin was consumed for 15 days, 3 repeats of the 5-day menu cycle. One-half of the subjects (subjects 1-5) first consumed whole bran muffins then dephytinized bran muffins and one-half (subjects 6-10) consumed them in the reverse sequence. Stools were collected and pooled the first 5 days and stools and urine were collected and pooled for the last 10 days. Apparent absorption (intake minus excretion in feces) was calculated for the 5- and 10-day periods, but balances were calculated only for the 10 day period. 

Figure 5. Iron balance of adult men consuming 36 g of whole wheat bran or dephytinized bran per day. The arrows and vertical bars (all subjects) represent mean I SD. Balances are for the last 10 days of a 15-day period in which each type of bran muffin was consumed. Solid symbols, with phytate open symbols,...

Whole Bran Muffin Dephytinized Bran Muffin ... 

Subjects 1-5 consumed whole bran muffins the first 15 days then consumed dephytinized bran muffins. Subjects 6-10 consumed the muffins in the reverse sequence. 

Binding of nutritionally important cations to dietary fiber has recently been introduced as a possible cause for poor utilization by humans of iron from diets high in vegetables and unrefined cereals. Reinhold et al. (J2) and Ismail-Beigi et al. (33) have demonstrated that the fiber component of wheat bread and bran binds iron even after the phytate has been extracted by dilute acid. In our study, the water-insoluble fraction (containing most of the neutral detergent fiber of the bran) of enzymatically dephytinized wheat bran did not inhibit, whereas... 

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