Vitamin C: Ascorbic acid sources and deficiency
Vitamin C (ascorbic acid) is naturally found in variety of foods. Vitamin C aka ascorbic acid is needed for normal functioning of body. It has many functions in body. its is essential for normal functioning of the healthy body.
Functions of Vitamin C
Vitamin C is needed for hydroxylation reaction. Hydroxylation is a reaction that takes place in many many needed materials synthesis in the body and also detoxification of many products of metabolism. One such particular reactionnis it takes part in hydroxylation of lysine and proline in pracollagen to form collagen. Collagen is much needed as building material for variuos tissues of the human body. In human body the signal is carried from brain to various organs and it is carried by series neurons. The signal is to be carried from one neuron to other. At the site of neuronal junction it is carried by certain chemicals from one neuron to other. those are neurotransmitters. Vitamin C is also involved in neurotransmitter formation. Number of neurotransmitters need vitamin C at some stage in their formation.
- Vitamin C is needed for conversion of dopamine to norepinephrine and tryptophan to serotonin
- Vitamin C is needed for cholesterol metabolism (conversion of cholesterol to steroid hormones and bile acids)
- Vitamin C is needed for the biosynthesis of carnitine.
- Vitamin C functions to maintain the iron and copper atoms, cofactors of the metalloenzymes, in a reduced (active) state.
- Vitamin C is an important antioxidant (electron donor) in the aqueous milieu of the body.
- Vitamin C enhances nonheme iron absorption, the transfer of iron from transferrin to ferritin
- The formation of tetrahydrofolic acid and thus can affect the cellular and immunologic functions of the hematopoietic system.
Recommended daily allowance (RDA) of Vitamin C
Humans can not form Vitamin C by themselves in the body. Human need to acquire Vitamin C from the outside. Humans take their daily needed vitamin C from their food. The requirement of Vitamin C changes according to age.
- For age o to 6 months the daily requirement is 40 mg.
- For 6-12 months daily requirement of vitamin C is 50 mg.
- For older children, For 1 – 3 years age daily requirement of vitamin C is 15 mg.
- For 4 – 8 yrs age daily requirement is 25 mg.
- For 9 – 13 yrs age daily requirement is 45 mg.
- For 14 – 18 yrs age daily requirement is 65 – 75 mg.
- The recommended dietary allowances during pregnancy and lactation are 85 mg/day and 120 mg/day, respectively.
- The requirement for ascorbic acid is increased during infectious and diarrheal diseases.
- Children exposed to smoking or environmental tobacco smoke also require increased amounts of foods rich in ascorbic acid.
Sources of Vitamin C
As we discussed earlier humans can not form ascorbic acid by themselves they need to take it from diet. Following are some foods rich in.
- Citrus fruits and fruit juices
- Green leafy vegetables
Vitamin C is easily destroyed by prolonged storage, overcooking, and processing of foods. Absorption occurs in the upper small intestine by an active process or by simple diffusion when large amounts are ingested. is not stored in the body but is taken up by all tissues; the highest levels are found in the pituitary and adrenal glands. The brain ascorbate content in the fetus and neonate is manyfold higher than the content in the adult brain, a finding probably related to its function in neurotransmitter synthesis.
Deficiency of Vitamin C
If the mother is taking adequate amount of Vitamin C in her diet during pregnancy the fetus will adequate amount. This is transferred from mother to fetus by placenta.If mother is taking adequate amount of Vitamin C in her diet during lactation the baby will get adequate from breast milk. Commercial formulae usually contain adequate amount. Breast milk contains sufficient to prevent deficiency throughout infancy. Infants whose diet contains pasteurized or boiled animal milk have increased risk of developing deficiency if the other sources are also lacking in the diet. Neonates whose feeding has been delayed because of clinical condition can also suffer from ascorbic acid deficiency.Children who choose a limited diet or those on fad diets are at risk for this deficiency.A deficiency of vitamin C results in the clinical presentation of scurvy, the oldest nutritional deficiency disease to be recognized. Children fed predominantly heat-treated (ultrahigh-temperature or pasteurized)milk or unfortified formulas and not receiving fruits and fruit juices are at significant risk for symptomatic disease. In scurvy, there is defective formation of connective tissues and collagen in skin, cartilage, dentine, bone, and blood vessels, leading to their fragility. In the longbones, osteoid is not deposited by osteoblasts, cortex is thin, and thetrabeculae become brittle and fracture easily.
The early manifestations are
- Loss of appetite
- Low-grade fever
- Musculoskeletal pain
- Tenderness in the legs.
These signs and symptoms are followed
- Leg swelling—most marked at the knees and the ankles
- Pseudoparalysis. The infant might lie with the hips and knees semiflexed and the feet rotated outward.
- Subperiosteal hemorrhages in the lower limb bones sometimes acutely increase the swelling and pain, and the condition might mimic acute osteomyelitis or arthritis.
- A “rosary” at the costochondral junctions and depression of the sternum are other typical features.
- The angulation of scorbutic beads is usually sharper than the angulation of a rachitic rosary.
- Gum changes are seen in older children after teeth have erupted and are manifested as bluish purple, spongy swellings of the mucous membrane, especially over the upper incisors.
- Anemia, a common finding in infants and young children with scurvy, is related to impaired iron absorption and coexistent hematopoietic nutrient deficiencies including iron, vitamin B12, and folate.
- Manifestations of scurvy include petechiae, purpura, and ecchymoses at pressure points; epistaxis; gum bleeding; and the characteristic perifollicular hemorrhages.
- Other manifestations are poor wound and fracture healing, hyperkeratosis of hair follicles, arthralgia, and muscle weakness.
Diagnosis of Vitamin C deficiency:
- The diagnosis of vitamin C deficiency is usually based on the characteristic clinical picture, the radiographic appearance of the long bones, and a history of poor intake.
- The typical radiographic changes occur at the distal ends of the long bones and are particularly common at the knees.
- The shafts of the long bones have a ground-glass appearance because of trabecular atrophy.
- The cortex is thin and dense, giving the appearance of pencil outlining of the diaphysis and epiphysis.
- The white line of Fränkel, an irregular but thickened white line at the metaphysis, represents the zone of well-calcified cartilage.
- The epiphyseal centers of ossification also have a ground-glass appearance and are surrounded by a sclerotic ring .
- The more specific but late radiologic feature of scurvy is a zone of rarefaction under the white line at the metaphysis.
- This zone of rarefaction (Trümmerfeld zone), a linear break in the bone that is proximal and parallel to the white line, represents area of debris of broken-down bone trabeculae and connective tissue.
- A Pelkan spur is a lateral prolongation of the white line and may be present at cortical ends.
- Epiphyseal separation can occur along the line of destruction, with either linear displacement or compression of the epiphysis against the shaft
- Subperiosteal hemorrhages are not visible using plain radiographs during the active phase of scurvy.
- However, during healing the elevated periosteum becomes calcified and radiopaque sometimes giving a dumbbell or club shape to the affected bone.
- MRI can demonstrate acute as well as healing subperiosteal hematomas along with periostitis, metaphyseal changes, and heterogeneous bone marrow signal intensity, even in absence of changes in plain radiographs.
- Gelatinous transformation of bone marrow, on aspiration, has been reported in children where the procedure was done on suspicion of a malignancy.
- Vitamin C supplements of 100-200 mg/day orally or parenterally.
- The clinical improvement is seen within a week in most cases.
- The treatment should be continued for up to 3 mo for complete recovery.
- Breastfeeding protects against vitamin C deficiency throughout infancy.
- In children consuming milk formula, fortification with this vitamin must be ensured.
- Children consuming heat-treated milk should consume adequate vitamin C–rich foods in infancy.
- Dietary or medicinal supplements are required in severely malnourished children, and chronic debilitating conditions such as malignancies and neurologic disorders.
- Daily intake of <2 g of vitamin C is generally without adverse effects in adults.
- Larger doses can cause gastrointestinal problems, such as abdominal pain and osmotic diarrhea.
- Megadoses of vitamin C should be avoided in patients with a history of urolithiasis or conditions related to excessive iron accumulation such as thalassemia and hemochromatosis.
- There is a paucity of data regarding this toxicity in children.
- The following values for tolerable upper intake levels are extrapolated from data for adults based on body weight differences: age 1-3 yr, 400 mg; age 4-8 yr, 650 mg; age 9-13 yr, 1,200 mg; and age 14-18 yr, 1,800 mg.