Everybody wants to improve the immune system to avoid infections, specially COVID-19. Vitamin C is the nutrient connected with immune system. It is often prescribed in short courses to promote wound healing and for faster recovery from infections, including cold. So it has been the interest of researchers in COVID-19 also.
Large doses of intravenous Vitamin C are being tried in COVID-19 critical patients on ventilators in China. The results are still not out. In Australia, researchers reported that they did not find any benefit in using Vit C, while the U.S. is planning to try a combination of Vitamin C, Vitamin D, Zinc and hydroxychloroquine for prevention. Many of the internet sites offer vitamin C as immune boosters. Caution is required in consuming mega doses of vitamins without prescriptions, especially for long periods.
A 74-year-old man in Belgium landed up in the hospital with weakness and vomiting. He was found to have severe kidney failure. He was dialysed and his kidney biopsy showed deposition of oxalate crystals, responsible for the kidney failure. On probing further it was found that he had been consuming for one week a “rejuvenating powder”, which he had bought online. The powder on analysis was found to be Vitamin C.
Vitamin C or Ascorbic acid is a water-soluble essential nutrient. Being water soluble, it is not stored in the body and requires daily intake. It is a powerful antioxidant with an important role in controlling infections and promoting healing of wounds. It has numerous functions such as synthesis of collagen (important component of bones, cartilage, nervous system, immune system etc) chemical messengers in brain and hormones. Deficiency of Vitamin C is rare and but when it occurs, it is called scurvy. It was reported in sailors in the past since they had no access to fruit and vegetables. It manifested with bleeding gums, delayed wound healing, skin spots, hair loss and anaemia.
The daily requirement of Vitamin c is 90mg in adult males, 75mg for females which increases to 120 mg in pregnancy. Smokers require additional 35 mg since smoking depletes Vitamin C. The source of Vitamin C is fruits, especially citrus fruits, and vegetables. Sailors were given an orange daily to prevent scurvy. Heat destroys Vitamin C. So prolonged cooking and leaching of the water can reduce the intake of the Vitamin. The Vitamin C consumed after absorption is metabolised in the body to oxalate and is removed by the kidneys.
Large doses of Vitamin C called mega doses are popular to improve the immunity and promote wound healing. The scientific evidence for this is lacking or at best, controversial. Similarly mega doses have been taken for common cold. Normally the body can cope with this high dose by reducing the absorption and increasing the oxalate loss in urine. But in some people the oxalate can get deposited in the kidneys resulting in kidney failure. This is likely in patients with intestinal disorders and pre-existing kidney disease. The toxic dose reported has been anywhere from 480 mg to several grams taken over variable periods. Fortunately this is a rare complication but lay people and physicians should be aware since there is popular concept that extra vitamins in large doses are helpful during stressful situations. Of course, the toxicity of large dose oil soluble vitamins like Vitamin A and D are well known since they produce high calcium in blood leading to stones and kidney failure.
The Eskimos traditionally would never eat the polar bear whose meat is very rich in vitamin A and D. It is very important that we maintain a balanced diet, regular exercise and exposure to sunlight as a routine in life. Mega doses of vitamins are best avoided without monitoring.