Fiber phytate

Hallberg, L. (1987). Wheat fiber, phytates and iron absorption. Scand. J. Gastroenterol. Suppl. 129, 73-79. 

The behavior of minerals is often influenced by the presence of other food constituents. The recent interest in the beneficial effect of dietary fiber has led to studies of the role fiber plays in the absorption of minerals. It has been shown (Toma and Curtis 1986) that mineral absorption is decreased by fiber. A study of the behavior of iron, zinc, and calcium showed that interactions occur with phytate, which is present in fiber. Phytates can form insoluble complexes with iron and zinc and may interfere with the... 

Requirement. The Mn requirement of chicks fed a casein-dextrose diet low in fiber, phytate and excess nutrients is 14 ppm (7,21). The National Research Council (39) has set a requirement of 60 ppm in conventional poultry diets. Because of the potential negative effect of conventional feedstuffs (see Bioavailability Section) on Mn bioavailability, the estimate of 60 ppm seems appropriate. 

The major fraction of iron in wheat bran is monoferric phytate, which is soluble and equilibrates with the miscible dietary nonheme iron pool of a meal. The di- and tetra-ferric phytates are much less soluble than monoferric phytate and probably do not equilibrate with the miscible nonheme iron pool of a meal. Bioavailability studies using either ferric phytate or sodium phytate must be evaluated in light of the form of ferric phytate or whether an insoluble ferric phytate may have been produced in the food. Wheat bran depresses absorption of dietary nonheme iron by humans. On the basis of available evidence, that effect of wheat bran cannot be unequivocally attributed to either the phytate or fiber component alone and might be influenced by interactions between the fiber, phytate and iron in the whole bran. Adult men maintained adequate positive iron balance when they consumed 36 g of whole bran each... 

Graf, E. and Eaton, J.W. (1985). Dietary suppression of colonic cancer. Fiber or phytate. Cancer 56, 717-718. 

Ali HI and Harland BF (1991) Effects of fiber and phytate in sorghum flour on iron and zinc in weanling rats - a pilot-study . Cereal Chemistry, 68, 234-238. 

Might antagonize verapamil Might induce hypercalcemia with thiazide diuretics Fiber laxatives (variable), oxalates, phytates, and sulfates can decrease calcium absorption if given concomitantiy Phenytoin, barbiturates, carbamazepine, rifampin increase vitamin D metabolism... 

Many other dietary factors have been reported to affect calcium bioavailability. Phytate, fiber, cellulose, uronic acids, sodium alginate, oxalate, fat (only in the presence of steatorrhea), and alcohol have been reported to decrease calcium bioavailability (15). Lactose and medium chain triglyceride increase it (15). FTuoride also affects calcium retention primarily by stimulating bone formation thereby decreasing calcium excretion (33-38). The effects of fluoride on calcium utilization have been variable (34,38,39). 

Without considering the aomplexity of additional interactions of phytate and Ca2+ with other polyvalent cations, proteins, and fiber, Figures 3 and 4 predict that the progressive elimination of bran in Table II lowers the concentration of soluble Ca2+. This effect is especially pronounced in the bread, where part of the remaining phytate was hydrolyzed by yeast phytase during leavening (Table II). These conclusions and their implications... 

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. 

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. 

Wheat bran has been the fiber source most commonly used to study effects of dietary fiber on calcium absorption in controlled laboratory studies. However, wheat bran and other forms of fiber as they occur in food products present several disadvantages in terms of definition and by concurrently altering intakes of other substances or materials known or suspected of having an adverse effect on the bioavailability of calcium such as phytates and oxalates (5,13,17,22-28). Several studies have been conducted which have sought to separate or compare the effects of phytate and fiber... 

Thus, it may be that the combination of high phytate and high fiber diets is more detrimental to calcium absorption than is either calcium absorption inhibitor by itself. 

Wisker E, R. Nagel, T. K. Tanudjaja, and W. Feldheim. Calcium, magnesium, zinc, and iron balances in young women effects of a low-phytate barley-fiber concentrate. Am J Clin Nutr 1991 54(3) 553-559. 

The recent enthusiasm for high fiber foods may carry a special challenge in considering food/drug toxicities. Vegetable fiber diets have been shown to reduce the toxicity of some drugs for animals (30). Presumably, phytates hold inorganic ions in a clathrate matrix that prevents absorption of the metal from the gut, other substances, e.g. bile acids, may also be bound (31). The bioavailability of iron as influenced by phytates in cereal foods via the formation of... 

Unstabilized bran and polish have been used almost exclusively for animal feed, due to the bitter flavor that develops from the lipolytic action of enzymes on the oil found in them. However, development of a thermal process that inactivates the lipases has resulted in a stabilized rice bran product that is suitable for the food industry. The impressive nutritional qualities of the oil, fiber, carbohydrate and proteins of rice bran have made it a valuable food material. Removal of fiber from the bran by physical K,J7or enzymic1819 processes produces a milk-like product having desirable nutritional and functional properties. The nutritional composition of the rice bran milk product described by California Natural Products has been shown to match the nutritional requirements of an infant formula. Originally, the anti-nutritional factor of the residual phytates was of concern. However, as of 2005, phytase enzymes are suitable for use to break down these phytates. 

Manganese is a nutritionally important trace element for chicks. Dietary energy and protein sources contain very little bioavailable Mn, and these feed ingredients reduce the biopotency of inorganic Mn supplements. This adverse effect is exerted primarily in the intestine as a result of reduced Mn absorption and is mediated by the fiber and/or ash components of the feedstuffs. Gut absorption efficiencies are higher when a phytate-and fiber-free casein-dextrose diet is fed than when a corn-soybean meal diet is fed. Dietary interrelationships exist between Mn and Co and between Mn and Fe. Cobalt increases Mn absorption and may precipitate Mn toxicosis. Excess dietary Mn reduces Fe utilization, but excess Fe does not affect Mn utilization. Eimeria acervulina infection increases Mn absorption. 

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