Why can ascorbic acid (Vitamin C) be irritating?

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Last updated: May 15, 2025View editorial policy

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From the Guidelines

Vitamin C can be irritating due to its potential to cause gastrointestinal disturbances, such as diarrhea, when taken in high doses. According to the study by the Institute of Medicine Food and Nutrition Board 1, the tolerable upper intake level for vitamin C is 2,000 mg/day, and adverse effects such as diarrhea and other gastrointestinal disturbances may occur when this level is exceeded.

Key Points to Consider

  • The recommended dietary allowance (RDA) for vitamin C is 75 mg/day for women and 90 mg/day for men 1
  • High doses of vitamin C, particularly above 2,000 mg/day, may lead to gastrointestinal disturbances 1
  • Vitamin C can also act as a pro-oxidant and a source of free radicals under certain conditions, which may have negative health implications 1
  • In patients with haemochromatosis, high-dose oral vitamin C supplementation has been associated with acute deterioration of cardiac function and acceleration of iron deposition 1

Recommendations for Safe Use

  • To minimize the risk of irritation, it is recommended to take vitamin C supplements in moderation and within the recommended dietary allowance 1
  • Individuals with haemochromatosis or iron overload should avoid supplemental vitamin C, especially in high doses, and consult with a physician before taking any supplements 1
  • Fruit juices and fruits, especially citrus fruits, should be consumed in moderation and not in combination with other foods due to their vitamin C content 1

From the FDA Drug Label

  1. OVERDOSAGE Overdose with ascorbic acid may cause nausea, vomiting, diarrhea, facial flushing, rash, headache, fatigue or disturbed sleep.

Vitamin C can be irritating due to potential overdose side effects, including:

  • Gastrointestinal symptoms such as nausea, vomiting, and diarrhea
  • Dermatological symptoms such as rash and facial flushing 2

From the Research

Vitamin C Irritation

  • Vitamin C, also known as ascorbic acid, is a water-soluble vitamin that can be irritating in certain situations, although the provided study does not directly address this issue 3.
  • The study focuses on the benefits and functions of vitamin C, including its role in bone formation, wound healing, and immune system support 3.
  • While the study highlights the importance of vitamin C in managing various diseases, it does not provide information on potential irritating effects 3.
  • There is no direct evidence in the provided study to explain why vitamin C can be irritating, suggesting that further research may be necessary to understand this aspect of vitamin C 3.

Professional Medical Disclaimer

This information is intended for healthcare professionals. Any medical decision-making should rely on clinical judgment and independently verified information. The content provided herein does not replace professional discretion and should be considered supplementary to established clinical guidelines. Healthcare providers should verify all information against primary literature and current practice standards before application in patient care. Dr.Oracle assumes no liability for clinical decisions based on this content.

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