Vitamin C (ascorbic acid) is one of nature’s wonders and is needed every day for the body to function normally. It is an excellent anti-oxidant, which boosts the immune system and helps the body fight off infections such as colds. It is needed for maintenance of healthy connective tissues, which is essential for wound healing, and it may also help to prevent blood clots and hardening of the arteries. It improves iron and calcium absorption and plays a role in amino acid and hormone formation.
The human body does not store or manufacture vitamin C, so it has to be obtained daily from foods such as citrus fruits, strawberries, blackcurrants, peppers, vegetables, and parsley. One large orange or a cup of strawberries or red peppers is enough to satisfy the daily requirements for most people.
Vitamin C deficiency is more common than overdosing because an overdose from natural sources is almost impossible. Many people take the vitamin as a supplement to avoid a deficiency, and in this case an overdose can occur. The symptoms of overdose vary from one person to another because they involve interactions with other vitamins and minerals in the food. If you are taking supplements and suspect you are taking too much, cut down gradually rather than stopping at once.
How Much Vitamin-C Do We Need?
The recommended daily allowances (RDAs) of vitamin C change from time to time and from one health authority to another. The most commonly seen range quoted for adults is 65 mg to 90 mg daily (with smokers needing more than non-smokers) and most authorities agree that any amount over around 300 mg is excreted in the urine, causing it to be bright yellow.
It is relatively easy to get enough vitamin C from the daily diet, but many people take supplements. The Merck Manuals Online Medical Library warns against taking more than 2,000 mg per day, and yet some take doses as high as 10 grams per day in the belief that such doses can slow or reverse the progression of cancer or atherosclerosis. Such benefits are not proven, and these doses can cause overdose symptoms.
Effects of Short-term Vitamin C Overdose
Taking too much vitamin C for a short time can cause stomach aches, bloating, cramps, nausea, headaches, heartburn, and diarrhea, which can in turn lead to dehydration. Overdosing on vitamin C has also been blamed for urinary tract infections, and extremely high doses have been linked to back pain. Taking megadoses even for a short period can cause copper levels to drop dramatically, resulting in an inflammatory response, including eye problems such as conjunctivitis.
Effects of Long-term Vitamin C Overdose
Taking megadoses of vitamin C for long periods results in the body becoming dependent on the high doses, and ‘rebound scurvy’ can occur if the dosage is reduced or supplements are stopped. This is most often seen in the babies of mothers taking megadoses during pregnancy. When the baby is born rebound scurvy can cause a loss of appetite, failure to gain weight, irritability, dry and rough skin, bleeding gums, loose teeth, weak muscles, and wounds that do not heal. As the baby grows, bone formation may be defective and fibrous tissue may form in the joints.
Long-term effects can also occur if the supplementation continues at a high dosage. The body breaks vitamin C down into oxalate, which is excreted in urine, but if in large doses the oxalate can form kidney stones. Excess vitamin C can also result in vitamin B12 deficiency in people with glucose-6-phosphate dehydrogenase deficiency, which is common in people with dark skin. Vitamin C can also reduce the intake of zinc and manganese, and reduce the body’s stores of copper. Deficiencies in these minerals can cause depletion of glycogen stores in the liver and soft bones.
Vitamin C is one of the most important vitamins we need, but as with most things, you can have too much of a good thing and it is wise to monitor for possible side effects if you do decide to take supplements.
