COMBINED EFFECTS OF VARIOUS TYPES OF DIETARY FIBER AND PROTEIN ON IN-VITRO CALCIUM AVAILABILITY

The effect of the nature of dietary fiber was determined by measuring soluble and ionic calcium using an in. vitro method. Results show the existence of a chemical interaction between calcium and fiber and/or p rotein. Lignin, oat bran, and wheat bran, which contain endogenous pro tein and phytic acid, with or without added protein, reduced calcium a vailability by 2-20% possibly through the formation of stable and inso luble complexes between fiber/phytic acid and calcium. When combined w ith fiber (with the exception of pectin), beef and casein had no signi ficant effect on soluble calcium. When compared with the fiber-free co ntrol, soy and lignin decreased soluble calcium. As well, soy, wheat b ran, lignin, and cellulose decreased ionic calcium, suggesting an inte raction effect.