A 52 year old female patient complains of pain in her abdomen. General examination reveals BMI 30 Kg/m2. X-ray examination reveals osteoporotic changes. Doctor suspects impaired absorption of calcium in this patient. All of the following could be the reason for this except:
Phytic acid (inositol hexaphosphate) in cereals binds calcium in the intestinal lumen, preventing its absorption. Other minerals, including zinc are also chelated by phytate.
This is mainly a problem among people who consume large amounts of unleavened whole-wheat products; yeast contains an enzyme, phytase, that dephosphorylates phytate, so rendering it inactive.
High concentrations of fatty acids in the intestinal lumen, as a result of impaired fat absorption, can also reduce calcium absorption by forming insoluble calcium salts; a high intake of oxalate can sometimes cause deficiency since calcium oxalate is insoluble.

Reference:  HARPERS ILLUSTRATED BIOCHEMISTRY30th, Page No: 541
Inositol hexaphosphate in cereals
High intake of oxalate
High concentrations of fatty acids in the intestinal lumen
Decreased iron intake