Why is calcium supplementation recommended in short bowel syndrome?

Why is calcium supplementation recommended in short bowel syndrome?

• A. To increase oxalate absorption
• B. To reduce calcium absorption
• C. To competitively bind oxalate with fatty acids in the lumen, reducing oxalate absorption
• D. To prevent phosphate binding

Answer: (C)

In short bowel syndrome, fat malabsorption leaves fatty acids in the gut lumen that bind calcium to form insoluble soaps, which lowers the amount of free calcium available to bind oxalate. When oxalate is not bound by calcium, it is readily absorbed, increasing urinary oxalate and the risk of calcium oxalate kidney stones. Calcium supplementation provides more luminal calcium, so oxalate can bind to calcium and form insoluble calcium oxalate that isn’t absorbed. This competitive binding of calcium to oxalate reduces oxalate absorption and helps prevent stone formation. Taking calcium with meals can enhance this effect since dietary oxalate is present then.

In short bowel syndrome, fat malabsorption leaves fatty acids in the gut lumen that bind calcium to form insoluble soaps, which lowers the amount of free calcium available to bind oxalate. When oxalate is not bound by calcium, it is readily absorbed, increasing urinary oxalate and the risk of calcium oxalate kidney stones. Calcium supplementation provides more luminal calcium, so oxalate can bind to calcium and form insoluble calcium oxalate that isn’t absorbed. This competitive binding of calcium to oxalate reduces oxalate absorption and helps prevent stone formation. Taking calcium with meals can enhance this effect since dietary oxalate is present then.