The Atkins diet has also come under criticism for its supposed ability to increase the risk of osteoporosis. The diet's high-protein nature increases acidity in the bloodstream, in response to which the body liberates alkaline compounds such as carbonate and citrate from the bone. This involves loss of calcium from the bone, too. This mechanism has been taken to explain why, when people are fed a high-protein diet, higher levels of calcium are detected in their urine.