2. Phosphorus

3. Learning Objectives Dietary sources Daily Requirements Metabolism
Important functions and
Deficiency diseases

4. Phosphorous P At. No. 15 Atomic Mass: 30.77

5. PHOSPHORUS

6. Dietary Source
Present in all foods, Dietary deficiency is therefore unknown.
Distribution is similar to Ca++ . Adequate, intake of one ensures that of the other.
Best sources (Milk and milk products)
Lean meat is also a good source.

7. Recommended Dietary Allowance
Infants Up to 6 months mg
6 m – 1.0 year mg
Children 1 – mg
4 – mg
7 – mg

8. Recommended Dietary Allowance
Adults (Male/Females)
11 – mg
15 – mg
19 – mg
23 – mg mg
Pregnant and lactating women should take an additional 400 mg.

9. Absorption and Metabolism
Normally about 70% of dietary P is absorbed
(For calcium 10 – 30%)
Mid jejunum is the main site of absorption for free PO4 .
In ileum absorption occurs via active process.

10. Absorption and Metabolism
Most of phosphorus in food is in combined form, absorption requires splitting off of PO4 by intestinal enzymes (Phosphatases)
is hydrolyzed in GIT by Pancreatic & intestinal enzymes.

11. Absorption and Metabolism
Inorganic phosphorus is released and absorbed
Its absorption decreases during period of increased utilization of carbohydrate

12. Factors affecting absorption
Similar to Calcium like:
Enhancement by Vit D and
Inhibition by binding agents i.e. Iron and Aluminium.
Ca : P ratio in diet.
Excess of one causes, an increased excretion of other.

13. Ratio of P : Ca
Ideal 1 : 1 , Specially during the period of rapid growth (childhood), pregnancy and lactation.
Ratio in other age groups if different, have no serious adverse effect

14. In Infants
Care should be exercised as kidneys can’t handle high phosphate load.
For Prevention of hypocalcemic tetany Ca : P ratio be 1.5 : 1
Ratio should be reduced to 1:1 by age 1 yr

15. Distribution Phosphorus accounts for about 1% of TBW.
¼th of total body mineral matter
80 – 90% joined with Ca++ in bones and teeth (Ratio 2:1) as a component of calcium phosphate and is being constantly deposited and liberated from bone structure.
10 – 20% present in all cells as phosphate ion (PO=4)

16. Functions
Component of many compounds involved in many metabolic reactions.
Sugar – PO4 linkage in DNA and RNA
Phospholipids  Transport of fat in blood
Phospholipids  cell membrane control transport of substances into and out of cell

17. Functions Phosphorylation
Necessary for glucose absorption from intestine
Glucose uptake by individual cells
Resorption of glucose by kidney

18. Functions
Monosaccharides are Phosphorylated several times during metabolic break down to yield energy.
Involved in storage and release of Energy through high energy phosphate bond of ATP and ADP.

19. Functions Essential part of body’s delicate buffer system
Many B vitamins becomes active only when combine with phosphate.

20. Hypo-Phosphatemia Diminished Supply: Starvation Malnutrition
Vit D – Deficiency
Increased excretion / loss
Hyperparathyroidism
Hyper thyroidism
Renal defects

21. Hypo-Phosphatemia Intracellular shift of phosphorus
Glucose induced
Insulin induced
Respiratory alkalosis
Electrolytes administration
Hypercalcaemia
Hypomagnesimia

22. Hyper-Phosphatemia Endocrine disease 2. Renal Diseases
Increased growth hormones (acromegaly)
Hypo parathyroidism low calcium
Pseudo hypo parathyroidism
2. Renal Diseases
Chronic renal insufficiency
Acute renal failure

23. Hyper-Phosphatemia 3. Catabolic states Excess intake or Absorption
Stress or injury
Chemotherapy for malignant disease
Excess intake or Absorption
Laxatives or Enemas containing phosphate
Hyper vitaminosis – D

24. Excretion Phosphate level is regulated by urinary excretion
2 mg / dl is the renal thresh hold
500 mg / day is excreted in urine

25. Excretion General factors affecting intestinal absorption
Plasma concentration and Hydrolysis of PO4 esters by phosphatases in the kidney.
Decrease Ca++ intake will increase urinary PO4 excretion

26. Clinical Importance