Is high-dose vitamin C (Vitamin C) effective in treating Coronavirus disease 2019 (Covid-19)?

High-Dose Vitamin C Is Not Recommended for COVID-19 Treatment

There is no established evidence that high-dose vitamin C supplementation prevents or improves clinical outcomes of COVID-19, and routine use of supraphysiologic amounts of vitamin C is not recommended. 1

Current Evidence on Vitamin C for COVID-19

Guideline Recommendations

• The European Society for Clinical Nutrition and Metabolism (ESPEN) explicitly states that while it's important to prevent and treat micronutrient deficiencies, there is no established evidence that routine, empirical use of supraphysiologic or supratherapeutic amounts of micronutrients, including vitamin C, may prevent or improve clinical outcomes of COVID-19 1
• Current nutritional guidance focuses on ensuring adequate daily allowances of vitamins and trace elements for malnourished patients with COVID-19, rather than high-dose supplementation 1

Research Findings

• Despite theoretical benefits of vitamin C's antioxidant, anti-inflammatory, and immunomodulatory properties 2, clinical evidence supporting high-dose vitamin C for COVID-19 is limited
• A 2020 living systematic review found no studies meeting inclusion criteria to support or refute the use of vitamin C in COVID-19 treatment 3
• A small retrospective case series (n=12) suggested some potential benefits of high-dose intravenous vitamin C on inflammatory markers and oxygenation in severe COVID-19 patients, but this represents very low-quality evidence due to small sample size and study design 4

Nutritional Approach for COVID-19 Patients

General Nutritional Support

1. Nutritional Assessment:

   • Screen all COVID-19 patients for malnutrition risk using validated tools like MUST or NRS-2002 1
   • Diagnosis of malnutrition requires at least one phenotypic criterion and one etiologic criterion according to GLIM criteria 1

2. Energy and Macronutrient Requirements:

   • Energy: 27-30 kcal/kg body weight/day 5
   • Protein: 1.0-1.3 g/kg body weight/day 5
   • Fat and carbohydrates: Ratio between 30:70 (no respiratory deficiency) to 50:50 (with respiratory issues) 1, 5

3. Micronutrient Support:

   • Ensure provision of daily allowances of vitamins and trace elements for malnourished patients 1
   • Focus on correcting deficiencies rather than supraphysiologic dosing 1

Key Considerations and Pitfalls

Potential Risks of High-Dose Vitamin C

• Over-supplementation of vitamin C can lead to oxalate toxicity 6
• Intravenous administration requires medical supervision and monitoring
• May create false sense of security and delay proven treatments

Special Populations

• Patients with malnutrition are at higher risk for poor outcomes in COVID-19 1
• Older adults and those with comorbidities require careful nutritional assessment and support 1
• COVID-19 can cause nausea, vomiting, and diarrhea, impairing food intake and absorption 1

Practical Approach to Nutritional Support in COVID-19

1. For Outpatients/Mild Disease:

   • Maintain adequate intake of all nutrients through a balanced diet
   • Correct any identified deficiencies with standard supplementation
   • Continue regular physical activity while in quarantine 1

2. For Hospitalized Patients:

   • Early nutritional assessment and intervention within 48 hours 5
   • Oral nutritional supplements providing at least 400 kcal/day and 30g protein/day if needed 5
   • Monitor nutritional status regularly

3. For Critically Ill Patients:

   • Start enteral nutrition within 24-48 hours of ICU admission if indicated 5
   • Use standard, high protein polymeric formulas 5
   • Consider parenteral nutrition only when enteral nutrition is contraindicated or insufficient 5

While some ongoing clinical trials are investigating vitamin C for COVID-19, current evidence does not support the routine use of high-dose vitamin C supplementation. The focus should remain on comprehensive nutritional support and addressing specific deficiencies rather than empirical high-dose supplementation.