insoluble soap

in·sol·u·ble soap

soap made with a fatty acid and an earthy or metallic base (iron or calcium salts of fatty acids).
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However, high consumption of animal fats containing large amounts of saturated fatty acids such as palmitic acid and stearic acid is associated with high intake of calcium causes a type of reaction between fatty acid and calcium which results in the formation of insoluble soap and non-use of nutrients by poultry and eventually will excreted through feces (Sibbald and Price, 1977).
Therefore, it was concluded that the inclusion of fat in diet accompanying to Ca causes a reaction between fatty acid and Ca, which results in the formation of insoluble soap and non-use of nutrients, which eventually could excreted through feces (Sibbald and Price, 1977).
(5) Free palmitic acid tends to complex with minerals and form insoluble soaps with calcium ions that cannot be absorbed in the small intestine and are thus excreted in the faeces (Figure 3).
Michael Thun, vice president of cancer epidemiology at the American Cancer Society, "One possible mechanism by which calcium can reduce colon cancer risk is that it may complex with bile salts and form insoluble soaps." These insoluble soaps are then excreted, preventing bile salts from harming the colon.