Vitamin C supplements: Can a high dose damage your body?

High Doses Can Cause Diarrhoea: One of the most immediate side effects of high doses of Vitamin C supplements is gastrointestinal distress, including diarrhoea. When consumed at levels of around 2,000 mg daily, Vitamin C can cause osmotic diarrhoea. The body cannot absorb such a high quantity, resulting in water being drawn into the intestines to dilute the concentration, leading to this condition. This effect can vary among individuals but it remains a consistent risk with excessive consumption.

A Daily Dose of 1000 mg is Risky for Some: For those vulnerable to kidney issues, a daily intake of 1,000 mg or more of Vitamin C can be problematic. The body converts excess Vitamin C into oxalate, which may contribute to the formation of kidney stones.

Even in individuals without a previous history of kidney stones, excessive Vitamin C can increase the risk of stone formation. While not everyone will develop stones from high Vitamin C intake, those with certain predispositions like a family history of kidney stones or dietary factors should remain alert.

Apart from diarrhoea and kidney stones, high doses of Vitamin C can lead to stomach cramps, nausea, and insomnia. These are signs that the body is struggling to manage the overload and acting out against it.

Nutrient imbalance: An extra high dose of Vitamin C supplements can impair the body’s ability to process other nutrients. It can reduce levels of vitamin B-12 and copper while enhancing iron absorption to the extent that the body has excessively high levels of this mineral.

Reduces HDL: Evidence suggests that taking too many vitamin C supplements may affect the body’s ability to increase high density lipoprotein (HDL) or good cholesterol in people taking the combination drug of the vitamin niacin with the statin simvastatin.

How much does the body need? The Recommended Dietary Allowance (RDA) for Vitamin C varies by age, sex and life stage but generally doesn’t exceed 90 mg for adult men and 75 mg for adult women. Even for those needing increased intake due to factors like smoking or certain medical conditions, exceeding 2,000 mg daily—the Tolerable Upper Intake Level (UL)—is unnecessary and unsafe.

Remember that vitamin C supplements are usually unnecessary because most people can easily get enough of this vitamin by eating fresh foods, especially fruits and vegetables. Consult your healthcare practitioner if you need supplements in the first place.

(Dr Anurag Aggarwal is Consultant, Internal Medicine, Fortis Escorts Hospital Faridabad)