Ascorbic acid (vitamin C, sodium ascorbate) is water-soluble and found in citrus fruits, berries, tomatoes and greens, but its level in food is reduced by cooking, mincing and contact with copper utensils. Vitamin C can also be synthesised from non-food sources, and the synthetic form cannot be differentiated from the natural in any way.
Vitamin C is essential for the formation and maintenance of cartilage, bone and teeth, and is used in moderate amounts to promote the healing of wounds and during convalescence from prolonged illnesses. Unfortunately there is no evidence to support its use in preventing or treating the common cold. In one trial, 3000 Californian users of vitamin C supplements were evaluated for 10 years and had the same rate of illness and death as a control group of non-users.
The level of ascorbic acid in a blood sample can be measured. The normal value is 23 to 86 µmol/L (0.4 to 1.5 mg/100 mL).
The recommended daily dietary intake is 25 mg in infants, 30 mg in children and 40 mg in adults.
A lack fresh fruit and vegetables and a subsequent lack of vitamin C in the diet will result in the disease scurvy, which has the symptoms of impaired wound healing, loss of teeth, mouth ulcers and poor resistance to infections.
Excess vitamin C in the body from taking too many vitamin C (ascorbic acid) supplements may have several unusual effects including:
- increased blood levels of oestrogens which causes breast tenderness and menstrual period irregularities,
- increased risk of kidney stones,
- reduced absorption of vitamin B12,
- the development of pernicious anaemia,
- rebound scurvy in babies born to mothers who take too much vitamin C during pregnancy.
The level of vitamin C can be measured in the blood. If the patient stops vitamin C supplements long term complications are uncommon.