Phosphorus

Phosphorus the second most abundant element (after calcium) present in our bodies, makes up about 1 percent of our total body weight. It is present i every cell, but 85 percent of the phosphorus is found in the bones and teeth. In the bones, phosphorus is present in the phosphate form as the bone salt calcium phosphate in an amount about half that of the total calcium. Both these important minerals are in constant turnover, even in the bone structure.

The body uses a variety of mechanisms to control the calcium-phosphorus ratio and metabolism. The ratio of these two elements in the diet has been the subject of much recent interest. The typical American diet provides too much phosphorus and not enough calcium, leading to reduced body storage of calcium; thus, many of the problems of calcium deficiency discussed earlier may develop. Phosphorus and calcium can compete for absorption in the intestines. High consumption of meats or soft drinks increases phosphorus intake and may contribute to this imbalance. The ideal ratio of calcium to phosphorus in the diet is 1:1.

Phosphorus is absorbed more efficiently than calcium. Nearly 70 percent of phosphorus is absorbed from the intestines, although the rate depends somewhat on the levels of calcium and vitamin D and the activity of parathyroid hormone (PTH), which regulates the metabolism of phosphorus and calcium. Most phosphorus is deposited in the bones, a little goes to the teeth, and the rest is contained in the cells and other tissues. Much is found in the red blood cells. The plasma phosphorus measures about 3.5 mg. (3.5 mg. of phosphorus per 100 ml. of plasma), while the total blood phosphorus is 30-40 mg.. The body level of this mineral is regulated by the kidneys, which are also influenced by PTH. Phosphorus absorption may be decreased by antacids, iron, aluminum, or magnesium, which may all form insoluble phosphates and be eliminated in the feces. Caffeine causes increased phosphorus excretion by the kidneys.

Sources: Since phosphorus is part of all cells, it is readily found in food, especially animal tissues. Most protein foods are high in phosphorus. Meats, fish, chicken, turkey, milk, cheese, and eggs all contain substantial amounts. Most red meats and poultry have much more phosphorus than calcium-between 10 and 20 times as much-whereas fish generally has about 2 or 3 times as much phosphorus as calcium. The dairy foods have a more balanced calcium-phosphorus ratio. Seeds and nuts also contain good levels of phosphorus (although they have less calcium) as do the whole grains, brewer’s yeast, and wheat germ and bran. Most fruits and vegetables contain some phosphorus and help to balance the ratio of phosphorus to calcium in a wholesome diet.

In recent years, the increased consumption of soft drinks, which are buffered with phosphates, has been a concern. There may be up to 500 mg. of phosphorus per serving of a soft drink, with essentially no calcium. In 1970, the average per capita intake of soft drinks was 23 gallons, whereas in 1981, 39 gallons a year were consumed by the “average” person. Since some people do not drink any of these “beverages,” quite a number of people are drinking even more than the average amount of soda pops, and thus consuming a lot of phosphorus.

Functions: Phosphorus is involved in many functions besides forming bones and teeth. Like calcium, it is found in all cells and is involved in some way in most biochemical reactions. Phosphorus is vital to energy production and exchange in a variety of ways. It provides the phosphate in adenosine triphosphate (ATP), which is the high-energy carrier molecule in the body’s primary metabolic cycles. Phosphorus is important to the utilization of carbohydrates and fats for energy production and also in protein synthesis for the growth, maintenance, and repair of all tissues and cells. As inorganic phosphate in ATP, it is needed in protein synthesis and in the production of the nucleic acids in DNA and RNA, which carry the genetic code for all cells.

Phosphorus is also a component of the phospholipids, fat molecules essential to cell membranes; lecithin is the best-known phospholipid. It helps in fat emulsification and in other body functions. In the cell membranes, the phospholipids help maintain both fluidity and permeability, allowing the nutrients to pass in and out of the cells. The sphingolipids, involved in nerve conduction, also contain phosphorus. Phosphorus is combined with the B vitamins to assist their functions in the body; furthermore, phosphoproteins are contained in many enzyme systems.

In addition to its role in these processes and in skeletal growth and tooth development, phosphorus has a number of other functions. It helps in kidney function and acts as a buffer for acid-base balance in the body. Phosphorus aids muscle contraction, including the regularity of the heartbeat, and is also supportive of proper nerve conduction. This important mineral supports the conversion of niacin and riboflavin to their active coenzyme forms. As mentioned, parathyroid hormone regulates the phosphorus blood level and helps it carry out all these essential functions.

Uses: Phosphorus by itself is used in only a few medically significant conditions. It is not needed as frequently as calcium to balance the ratio between these two minerals. However, phosphorus has been used to treat many kinds of bone problems; it (along with calcium) helps in healing fractures by minimizing calcium loss from bones. It is used in the treatment of osteolmalacia, where there is decreased bone mineral content, and in osteoporosis, where total bone mass is decreased. Rickets has also been treated with phosphorus, as well as with calcium and vitamin D.

Rebalancing the calcium-phosphorus ratio in the diet can help reduce stress and many problems relating to calcium metabolism, arthritis being one example. Tooth and gum problems can be alleviated with dietary phosphorus, again in balance with calcium. Cancer research has revealed that cancer cells tend to lose phosphorus more readily than do normal cells, so phosphorus may be useful in the nutritional support of cancer patients; however, a high phosphorus-to-calcium intake is to be avoided.

Deficiency and toxicity: There is no known toxicity specific to phosphorus; however, high dietary phosphorus, as is found in a diet with meats, soft drinks, and other convenience foods, can readily affect calcium metabolism. Potential calcium deficiency symptoms may be more likely when the phosphorus intake is very high. A low calcium-to-phosphorus ratio in the diet increases the incidence of hypertension and the risk of colon-rectal cancer.

Problems of phosphorus deficiency are fairly uncommon, since it is so readily obtained in the diet; it is usually consumed in greater amounts than calcium and is readily absorbed. Relative deficiency of phosphorus can be caused by very high calcium intake or by taking a lot of antacids which can bind phosphorus. Aluminum, magnesium, and iron can interfere with phosphorus absorption. Low vitamin D intake can also lead to deficient body phosphorus.

Symptoms of phosphorus deficiency may include anorexia, weakness, weight loss, irritability, anxiety, stiff joints, paresthesias, bone pain, and bone fragility. Decreased growth, poor bone and tooth development, and symptoms of rickets may occur in phosphorus-deficient children. In adults, as mentioned, a low calcium-to-phosphorus ratio is most likely to generate problems. Osteoporosis (bone resorption) is often brought on by high phosphorus and low calcium intake. Other adult problems include skin disease, tooth decay, and even arthritis.

Requirements: The RDA for phosphorus is the same as that for calcium, 800 mg. for adults. However, the average dietary intake of calcium is low, at about 500 mg.; that for phosphorus is more like 1,500 mg. In pregnancy and lactation, as well as in children aged 11-18, the RDA is higher, at 1,200 mg. If the phosphorus intake is high or body levels are increased, we may need to take more calcium to achieve the desired 1:1 ratio to maintain biochemical homeostasis.

Phosphorus in small amounts like 100-200 mg. is often contained in multimineral or multivitamin formulas. It is unlikely that anyone takes phosphorus as a separate supplement.