Fiber also has been shown to impair the calcium absorbed from an entire meal, not just from the food in which it's found. However, neither oxalates nor fiber should present problems if calcium intake is liberal. But they may make it difficult to obtain enough calcium without eating dairy products. Other dietary factors that increase calcium loss include high intakes of phosphorus, protein, vitamin A, alcohol and caffeine. A nondietary factor is cigarette smoking.
Protein is an important nutrient, essential for the growth and repair of body cells.
But diets high in protein can cause increased calcium excretion. Some suggest taking magnesium to facilitate calcium absorption. Evidence, however, is scant. High magnesium intakes actually increase calcium loss in urine. Vitamin D is needed for proper absorption of calcium.