Phosphates and phytic Acid: Excess of phosphates lower calcium absorption. Phytic acid forms insoluble calcium salts and interferes with the absorption of calcium.
Reaction of the intestinal contents:Calcium is well absorbed at the normal pH of the intestines. If the contents become alkaline, calcium absorption is lowered due to the formation of insoluble tricalcium phosphate.
Fats and fatty acids: Faulty absorption of fats leading to the presence of large amounts of fatty acids interferes with calcium absorption, as insoluble calcium salts of fatty acids are formed and excreted in the faeces.
Protein: Higher levels in the diet help to increase the absorption of calcium.
Fibre: Presence of excess fibre in the diet interferes with the absorption of calcium.
Oxalic Acid: Oxalic acid present in certain foods form insoluble calcium oxalate complexes which are excreted in the faeces, thus lowering calcium absorption.