vitamin C has many roles and functions in the body. The C stands for citrus, wherein this vitamin was found first.
Functions of Vitamin C:
- It has an antioxidant activity.
- It promotes the absorption of iron.
- It is required for the formation of collagen.
- It acts as a coenzyme to convert proline to hydroxyproline and lysine to hydroxylysine. Both hydroxyproline and hydroxylysine are important for collagen synthesis.
- It helps with wound healing.
- It aids the metabolism of folic acid (vitamin B9), tyrosine, and tryptophan.
- It functions as a coenzyme in the conversion of tryptophan to 5 – hydroxytryptophan, which is the precursor to serotonin.
- It helps folic acid convert to its active form, tetrahydrofolic acid.
- It is important in the conversion of tyrosine to dopamine and dopamine to norepinephrine.
- It stimulates the adrenal glands to produce and release the hormones epinephrine, norepinephrine, and cortisol (stress hormone).
- It protects LDL cholesterol and vitamins B1, B2, B5, and B9 from oxidative damage.
- It supports the production of thyroid hormones.
- It boosts the immune system against infections (bacterial, viral, and fungal) by stimulating neutrophils and lymphocytes.
- It may reduce the risk of allergy by decreasing the production of histamine.
- It is a component of many drug – metabolizing enzyme systems.
- It may reduce the risk of toxicity with heavy metals, such as mercury, lead and arsenic.
- It reduces the incidence of certain cancers, especially esophageal and gastric cancers.
- It has a potential therapeutic role in the treatment of advanced cancers.
Food Sources and Absorption:
Foods high in vitamin C are citrus fruits (lime, lemon, orange, tangerine,
and grapefruit), rose hips, green peppers, broccoli, cherries, berries, papaya, tomatoes, potatoes, Brussels sprouts, parsley, asparagus, cabbages, and dark green leafy vegetables.
Vitamin C is absorbed well from the upper part of the small intestine. If dietary intake is less than 100 mg, almost 90% of vitamin C is absorbed. However, only 50% or less is absorbed when dietary intake is more than 1000 mg. The absorption of vitamin C is enhanced by flavonoids. The consumed vitamin C is used by the body within 2 hours and is metabolized to oxalic acid, threonic acid, and lyxonic acid. The body can store some vitamin C, about 65 mg per one kilogram of body weight. The highest concentrations of vitamin C in the body are in the adrenal glands, pituitary gland, eyes (especially the retinas), brain, testicles, and ovaries.
The daily requirement of vitamin C is increased in the following conditions (either due to decreased absorption or increased utilization):
- Smoking.
- Hemodialysis.
- Pregnancy.
- Stress.
- Infections.
- Trauma.
- Alcoholism.
- Fever.
- Consumption of antibiotics, corticosteroids, aspirin, or other pain – killers.
- Exposure to heavy metals, such as mercury, lead, arsenic, and cadmium.
- Exposure to environmental toxins, such as pesticides, herbicides, and carbon monoxide.
Athletic Benefits of Vitamin C:
- It protects the muscles from exercise – induced oxidative damage, promoting muscle growth.
- It may prevent from overtraining syndrome.
- It may speed up exercise recovery.
- It supports protein synthesis.
- It may have a protective effect against post – exercise myoglobinuria (PEM). See “Post – Exercise Rhabdomyolysis” under the section of “Athletic Disorders“.
- It may accelerate the healing process in strains and sprains.
Non – Athletic Benefits of Vitamin C: 
The following medical conditions may benefit from vitamin C:
- Anemia.
- Wound healing.
- Common cold.
- Infections.
- Stress.
- Cancers.
- Infertility.
- Bruising.
- Periodontal disease.
- Eye problems such as glaucoma, cataract, and age – related macular degeneration (AMD).
- Varicose veins.
- Cold sores.
- Asthma.
- Capillary fragility.
- Dysmenorrhea.
- Endometriosis.
- Inflammation (bursitis, bronchitis, cystitis, dermatitis, sinusitis, gastritis, and prostatitis).
- Compromised immune system.
- Osteoarthritis.
- Rheumatoid arthritis.
- Atherosclerosis.
- Discogenic back pain.
- High LDL cholesterol.
- Autism.
- Adrenal exhaustion.
- Substance (alcohol, nicotine, and caffeine) withdrawal support.
Vitamin C Deficiency:
Overt deficiency of vitamin C in adults occurs when dietary intake of vitamin C drops to below 10 mg per day. It leads to a disease called “scurvy”. The signs and symptoms of vitamin C deficiency include fatigue, delayed wound healing, easy bruising, loss of appetite, tiny hemorrhage, coiled hairs, inflamed and bleeding gums, joint swelling and tenderness, poor digestion, nose bleeding, and brittle bones.
Dosage and Side Effects:
For the RDA of vitamin C, see the table below. Though it is a part of any multivitamin products, it is also available as tablets, chewing pills, powders, effervescent, liquid forms, and injections. The usual dose of vitamin C is 1000 – 2000 mg per day. Some conditions may require higher doses.
The Recommended Daily Allowance (RDA) for Vitamin C
Age or Conditions | RDA for vitamin C |
Male, 14 – 18 years old | 75 mg |
Male, 19 years old and older | 90 mg |
Female,14 – 18 years old | 65 mg |
Female, 19 years old and older | 75 mg |
Pregnancy | 85 mg |
Breastfeeding | 120 mg |
Consuming more than 2000 mg of vitamin C in a single dose could lead to abdominal cramp, nausea, and diarrhea. Other symptoms include skin sensitivity (flushing of the face), burning feeling while urinating, destruction of the red blood cells (hemolysis), headaches, sleep disturbances, and false – negative guaiac reaction (stool exam will show no blood despite having blood in it).
Vitamin C should be avoided in the following conditions:
- Kidney stones, oxalate type.
- G6PD deficiency.
- Hemochromatosis.
Interactions:
- Aluminum – containing antacids: vitamin C may increase the absorption of aluminium and risk of toxicity. It should be taken 2 hours before or 4 hours after these kinds of antacids.
- Acetaminophen (Tylenol): vitamin C may decrease the urinary secretion of acetaminophen followed by an increase its blood level.
- Birth control pills: vitamin C may increase the blood levels of estrogen.
- Nonsteroidal anti – inflammatory drugs (NSAIDs) and aspirin: they increase urinary loss of vitamin C, leading to low levels of vitamin C in the body.
- Barbiturates: they may decrease the effectiveness of vitamin C.
- Fluphenazine: vitamin C may decrease the effectiveness of this medication.
