why do we need calcium and phosphorus
March 20, 2002 --
alone can't build strong bones and tissues. New research shows needs phosphorus to maximize its bone-strengthening benefits, and taking a lot of without enough phosphorus could be a waste of money. Researchers say it's the first time the two elements have been shown to be co-dependent for bone health. Both calcium and phosphorus are found naturally in dairy products, but most calcium and calcium-fortified foods and beverages don't contain phosphorus. More than half of all bone is made from phosphate, and small amounts are also used in the body to maintain tissues and fluids. But the study, presented at a meeting of experts, found that taking large amounts of calcium from can interfere with phosphorus absorption. Women trying to prevent or treat typically take 1,000-1,500 mg of calcium a day in the form of supplements. Researchers found this amount of calcium can bind up to 500 mg of phosphorus -- making it unavailable to the body. "Although this would present no serious problem for many people, it could impact women over 60 years of age who have diets that contain less than the National Academy of Sciences recommended daily allowance of 700 mg of phosphorus," says study author Robert P. Heaney, MD, of Creighton University, in a news release. "For these women, the usual calcium supplement, calcium carbonate, may block most of the absorption of phosphorus.
If this happens, the calcium won't do much good because bone material consists of both calcium and phosphorus," says Heaney. Researchers say their study shows both calcium and phosphorus are needed to support any increase in bone mass, and a calcium supplement that contains phosphorus would be preferable to one that provides calcium alone. Other dietary sources of phosphates include eggs, cereals, and meats. Rhodia, a major producer of calcium phosphates, partially funded this research. В 2002 WebMD, Inc. All rights reserved. Calcium and phosphorus are essential minerals found in the bone, blood and soft tissue of the body and have a role in numerous body functions. Phosphorus levels can affect calcium levels in the body, and vice versa. Parathyroid hormone, vitamin D and the kidneys all help to regulate calcium and phosphorus levels in the blood. The body must maintain certain levels of calcium and phosphorus in the blood. Parathyroid hormone, or PTH, and vitamin D work to keep these levels in balance. Calcium and phosphorus are absorbed into the blood through the small intestine after eating foods that contain these nutrients.
The bones will also release the nutrients to help maintain necessary blood levels. The parathyroid gland can sense an imbalance of calcium or phosphorus. If the calcium level is low, the parathyroid gland will release PTH, which tells the kidneys to produce more active vitamin D. This helps the body to absorb more dietary calcium and phosphorus through the intestine, tells the bone to release calcium and phosphorus into the blood and tells the kidneys to excrete more phosphorus in the urine. Calcium, Phosphorus and the Kidneys Healthy kidneys will eliminate excess phosphorus and calcium in the blood. If kidney function is impaired, the body will not be able to get rid of extra phosphorus. High phosphorus levels stimulate the release of parathyroid hormone, which can cause complications when the normal mechanism for bone mineral management does not work correctly. A high phosphorus level may also result in a low calcium level. Calcium binds with phosphate and is deposited in the tissue. A buildup of these deposits causes calcification in the tissue, which can disrupt normal organ function. People with chronic kidney disease should work closely with their dietitian and doctor to control phosphorus, calcium and parathyroid levels.
About 85 percent of the body's phosphorus and 99 percent of calcium are found in the bones. People with impaired kidney function are at greater risk for bone disease because they are more likely to have high phosphorus and PTH levels, which can lead to progressive bone loss. According to the Linus Pauling Institute, there is increasing concern for the effect of a high intake of phosphorus even in healthy individuals due to its possible impact on bone health. Excessive consumption of foods with phosphorus additives and a low calcium intake seem to be especially harmful. Calcium and phosphorus levels are controlled in part through dietary intake. The Food and Nutrition Board set the recommended dietary allowance of phosphorus at 700 milligrams daily. Sources of phosphorus include dairy products, meat, nuts, beans and foods that contain phosphorus additives such as convenience foods and colas. The RDA for calcium is 1,000 milligrams for most adults, though adolescents and older adults need more calcium. Sources of calcium include dairy products, soy, vegetables such as bok choy, broccoli and kale and beans such as pinto and red.
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