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Phosphorus and your healthIf you are to know one single thing about phosphorus (P), that probably should be about its ability to suppress calcium absorption, causing effects of calcium deficiency. Diets high in processed foods, meat and - especially - soft drinks, are high in phosphates, and are all but guaranteed to result in elevated phosphorus levels. Consequently, excessive phosphorus intake is rather common in the U.S. This doesn't necessarily result in osteoporosis - there is more than a single mechanism to it - but it certainly makes it more probable.
Phosphorus - usually in the form of phosphate group - is necessary to form many body proteins, phospholipids (main building blocks of cellular membranes), DNA's nucleic acids, adenosine triphosphate (molecular unit for energy storage, transport and usage at the cellular level), and for activating number of enzymes, including those needed for conversion of B2 and B3 vitamins into their active coenzyme forms.
Similarly to calcium, it aids muscle contraction, heartbeat and neural conduction in general.
Since phosphorus is a cellular buddy of sodium, they have some functional similarities, one of them being their effect on kidneys. Both, phosphorus and sodium are inflammatory to the kidneys when high, and degenerative when low, with the right kidney being affected primarily by sodium, and the left kidney by phosphorus (and protein) levels18. The ailment is remedied by correcting their imbalance.
Health effect of either high or low phosphorus levels are mainly similar: osteoporosis, arthritis, increased cancer risk, kidney stones, and some others.
Similarly to calcium, absorption of phosphorus requires a presence of vitamin D. If you are deficient in it, your phosphorus absorption will slow down, which can be actually good if you are ingesting too much of it (don't cut on vitamin D just for that reason, it wouldn't work well).
Phosphorus' blood level is controlled by parathyroid hormone (increase) and thyroid hormone calcitonin (decrease), adjusting the rate of its excretion through the kidneys. Since this is also how the body controls blood level of calcium, excessive phosphorus intake suppresses calcium blood levels, the effect re-enforced by phosphorus using vitamin D, also necessary for absorption of calcium.
Beside calcium, one of phosphorus' inhibitors is caffeine, which implies that higher phosphorus intake is partly offset by a higher caffeine intake.
In grains, phosphorus is bonded in phytates which makes its absorption - as well as absorption of other minerals - less efficient. Still, its average rate of absorption is about double that of calcium, or about 2/3 of the ingested quantity, which should be taken into account when assessing actual mineral intake from the food.
Phosphorus DRI (Dietary Reference Intakes, the most recent set of dietary recommendations set by the government) for an average healthy adult is set at 800mg, with short-term therapeutic intake of up to 2mg a day.
Best natural phosphorus food sources are liver, brewer's yeast, whole grains and dairy products.