Vitamin C toxicity: What are the signs?

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Vitamin C or ascorbic acid is a water-soluble vitamin necessary for the synthesis of collagen and neurotransmitters. It also possesses antioxidant properties that protect molecules in the body from damage by the oxidative free radicals.

The supplements that contain vitamin C are available over-the-counter and generally safe and well-tolerated, but some side effects can arise if high doses are taken.

Close look on toxicity

The usual side effects from large doses of vitamin C include stomach upset and diarrhea.

Since vitamin C is a water-soluble vitamin, the excess is flushed out as urine. It does not accumulate in the body which is why incidents of vitamin C toxicity are infrequent. The suggested dietary intake for women is 75 mg daily while 90 mg for men.

For those who smoke, add another 35 mg since smokers requires added antioxidant protection. The tolerable upper intake level of 2,000 mg has been established. If one consumes more than this level from supplements or food, the side effects might arise, but this is not likely to occur from the diet alone.

What are the potential side effects?

The usual side effects from large doses of vitamin C include stomach upset and diarrhea. Other effects that might arise include:

  • Headache
  • Abdominal cramping
  • Vomiting
  • Heartburn

These symptoms are not typically serious and settle once the high doses are stopped. The symptoms are triggered by the osmotic effect of excess vitamin C on the GI tract.

A high concentration of vitamin C in the intestines causes more water to be pulled into the intestines which leads to diarrhea and cramps.

Am I at risk for kidney stones?

Vitamin C can increase the amount of oxalate in the urine which also heightens the risk for developing kidney stones.

If an individual has a history of kidney stones, limit the intake of vitamin C to not more than 100 mg daily.

Considerations to bear in mind

It is important to note that vitamin C can lessen the effectiveness of some forms of prescription drugs including those used for cancer, AIDS and high cholesterol. It might even disrupt with the activity of blood-thinning drugs such as warfarin.

Since vitamin C augments the absorption of nonheme iron, high-dose supplements should not be taken with iron supplements.

The individual should also avoid large amounts of vitamin C if he/she has iron-related ailments such as hemochromatosis or thalassemia. If these conditions are present or using prescription drugs, a doctor should be consulted before using any vitamin C supplements.

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