General text about the lack of minerals can be found here.
Phosphorus is a chemical element, which is absolutely necessary for proper body function. Together with calcium, phosphorus ion (phosphate) is the main building block of bones and teeth. Relatively large amount of phosphorus is present in meat, milk, eggs and legumes.
The cause may be insufficient intake of phosphorus in the diet, but more serious forms are usually combined with impaired absorption of nutrients (and minerals) from the digestive tract or with chronic alcoholism. Decreased level of phosphate is usually observed in malnourished people, who are suddenly delivered large amount of food (so-called refeeding syndrome), when the phosphate molecules are consumed during increased metabolism of the missing nutrients. The decrease of phosphate in the blood can be associated with excessive activity of the parathyroid gland – hyperparathyroidism, which increases the level of calcium in the blood. The product of values of calcium and phosphate concentrations in blood is more or less constant and hypocalcemia may lead to decrease of phosphate level.
Lack of phosphorus may lead to disorders of bones and teeth. Teeth are often affected by dental caries; bones lose their strength and are easy to break. The patients also suffer from stiffness and joint pain and sometimes by unspecific symptoms such as fatigue and loss of appetite. Phosphate ions are important for stability of red blood cells and a significant phosphorus deficiency may be therefore followed by anemia.
Note: In refeeding syndrome, the deficiency of phosphates may be sudden and it may cause serious symptoms such as abnormal heart rhythm and subsequent cardiac arrest.
Phosphate level in blood may be evaluated from a sample of venous blood. However, it is important to have on mind that total amount of phosphorus may not always correlate with its serum level.
It is necessary to ensure adequate intake of phosphorus in the diet, and if this is not possible, then at least in food supplements. The daily intake for an average adult human is about 800 milligrams phosphorus a day. However, overdose with certain side effects is also possible as the phosphorus closely affects calcium levels and vice versa. Elevated phosphate levels tend to cause decrease of blood calcium leading to hypocalcemia. In addition, increased intake of phosphorus interferes with the absorption of iron and can cause symptoms of iron deficiency and its complications.