This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Biochemistry
[{'content': 'All of the following are the reasons for impaired absorption of calcium except: \nSelect and explain. \nA. Inositol hexaphosphate in cereals, B. High intake of oxalate, C. High concentrations of fatty acids in the intestinal lumen, D. Decreased iron intake', 'role': 'user'}, {'content': 'Answer: D \nExplanation: Phytic acid (inositol hexaphosphate) in cereals binds calcium in the intestinal lumen, preventing its absorption. Other\xa0minerals, including zinc, are also chelated by phytate. This is mainly a problem among people who consume large amounts\xa0of\xa0 unleavened\xa0 whole-wheat\xa0 products;\xa0 yeast\xa0 contains\xa0 an enzyme, phytase, that dephosphorylates phytate, so rendering\xa0it inactive. High concentrations of fatty acids in the intestinal lumen, as a result of impaired fat absorption, can also reduce\xa0calcium absorption by forming insoluble calcium salts; a high intake of oxalate can sometimes cause deficiency since calcium\xa0oxalate is insoluble.\nHARPERS ILLUSTRATED BIOCHEMISTRY30th, Page No: 541', 'role': 'assistant'}]