Phosphate

Phosphate sits mostly in your bones and teeth, where it forms the hard structure together with calcium. The rest works in your cells: it is the building block of ATP, the molecule with which every cell passes energy on, and of your genetic material and your cell membranes. In your blood only a small part circulates, and that part is what is measured. How much stays in your blood is regulated by three players together. Your kidneys excrete what you take in too much of. PTH, the hormone of the parathyroid glands, sets the kidneys to excreting more. Vitamin D raises the uptake from the gut. In that system phosphate is the value that usually moves as a consequence: if it rises, it is usually the kidneys that can get rid of less; if it falls, it is usually PTH pulling too hard or vitamin D letting too little in. Your report shows phosphate in mmol/L, often with a range for men and for women that differs slightly. Normal in a man from age 19 is 0.81 to 1.32 mmol/L and in a woman 0.81 to 1.40 mmol/L where the labs overlap; one lab starts lower, and the national agreement uses a slightly higher range, 0.9 to 1.5 mmol/L. A value just under 0.9 is therefore not called the same everywhere.

For anyone healthy who eats healthily, phosphate is a value that rarely moves: you get plenty of it, from meat, dairy, fish, nuts and grains, and your kidneys excrete the surplus. It becomes interesting when the kidneys filter less. Then phosphate slowly accumulates, the parathyroid glands respond with more PTH, and that pulls calcium out of bone. In chronic kidney disease phosphate is therefore one of the values followed, and a high phosphate there goes with a higher chance of calcification of the vessels. That is also where the lifestyle side sits. Phosphate from natural food is only half absorbed; phosphate from additives in processed food, cola, processed cheese, processed meat and ready meals is absorbed almost completely. Anyone who eats a lot of processed food takes in a phosphate load that healthy kidneys can handle, but that counts with weaker kidneys and with age. Less processed food is the lever, and that is the same lever as for blood pressure and weight. A low phosphate in healthy people is the other side of the same system: a vitamin D deficiency, which lets too little phosphate in, or too much PTH, which sends too much into the urine. Alcohol, eating too little and rapid refeeding after a period of eating little push it down too, because the cells then take up phosphate to make energy again.

A high phosphate comes, in order of how often it occurs, from: reduced kidney function, which cannot get rid of the surplus; plenty of phosphate additives from processed food, cola and processed cheese; too little PTH, after surgery in the neck; and rarely rapid cell breakdown or an excess of vitamin D. With a high value kidney function is the first look, and what you eat the second. A low phosphate comes from too little uptake or too much excretion: a vitamin D deficiency, a parathyroid gland making too much PTH, plenty of alcohol, eating too little or rapid refeeding afterwards, antacids that bind phosphate in the gut, and rarely an inherited leak in the kidney. A slightly low value in a healthy person is often simply the lab's floor, or a meal shortly before; phosphate fluctuates over the day. Read phosphate beside calcium, PTH, vitamin D and your kidney function. The order that helps: first the kidneys, then calcium, then PTH; in that system phosphate is usually the consequence and rarely the cause.