Brief Answer: both food and drugs Detailed Answer: Hi, I went through the query and understood your concern. Below am mentioning the factors Decreasing Calcium Absorption with explanation Oxalic Acid — Oxalic acid is a substance that binds to calcium directly in some plant-foods making calcium unavailable for absorption. The amount of calcium absorbed from foods high in oxalic acid, such as spinach, soybeans and cocoa, is small. However, the calcium absorption from other food sources consumed at the same meal will not be affected. Phytates — Phytates are substances found in pulses that can bind calcium in the intestine and decrease its absorption. Phytates, unlike oxalic acid, will bind the calcium from other food sources also consumed at the same meal. Dietary fiber — Although the effects are relatively small, high dietary intake of insoluble fiber, found in foods such as wheat XXXXXXX can bind calcium in the intestine decrease absorption. Medications — Long term use of medications, such as corticosteroids and anti-convulsants. If you need to take these medications for an extended period of time, consult your doctor about ways to help prevent bone loss. Also use of drugs that reduce gastric secretion like ranitidine, pantoprazole omeprazole will reduce calcium absorption. Laxatives or anything that induces diarrhea — Diarrhea can move substances through the intestine very rapidly, not leaving enough time for calcium to be absorbed. Excess consumption of minerals phosphorous and magnesium in proportion to calcium — The absorption of both magnesium and phosphorous requires vitamin D. If these minerals are consumed in excess, there will be less vitamin D available for aiding calcium absorption. Tannins in tea — Tannins are substances found in tea which can bind with calcium in the intestine, therefore decreasing its absorption. If one or more of these factors apply to you, you can compensate by increasing your calcium intake from food or supplements. I hope this information helps you. Feel free to ask if any further queries and I will be glad to answer them. Regards

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