Is it beneficial to take zinc and vitamin C during an active viral infection?

Zinc and Vitamin C Supplementation During Active Viral Infections

Routine supplementation with zinc and vitamin C during active viral infections is not recommended unless there is a proven deficiency, as there is no established evidence that supraphysiologic doses improve clinical outcomes. 1

Evidence on Zinc and Vitamin C in Viral Infections

Current Guidelines

• The European Society for Clinical Nutrition and Metabolism (ESPEN) explicitly states there is no established evidence that routine, empirical use of supraphysiologic amounts of micronutrients, including zinc and vitamin C, prevents or improves clinical outcomes in viral infections 2, 1
• ESPEN recommends ensuring only daily allowances of vitamins and trace elements for malnourished patients with viral infections 2
• The Surviving Sepsis Campaign specifically suggests against using zinc supplementation and ascorbic acid (vitamin C) in children with septic shock or sepsis-associated organ dysfunction 2

Zinc Supplementation

• For common cold specifically, zinc administered as zinc acetate or zinc gluconate lozenges at ≥75 mg/day and taken within 24 hours of symptom onset may significantly reduce the duration of common cold 2
• However, increased zinc intake beyond recommended levels can potentially reduce immune system function 3
• Low levels of zinc have been associated with adverse clinical outcomes during viral infections 2

Vitamin C Supplementation

• Regular vitamin C supplementation may have a consistent effect on the duration and severity of colds, but evidence for therapeutic use during active infection is less clear 2
• Over-supplementation of vitamin C can lead to oxalate toxicity 3

Practical Approach to Supplementation

When to Consider Supplementation

• Focus on correcting deficiencies rather than supraphysiologic dosing 1
• Consider zinc supplementation (75 mg/day) only if started within 24 hours of common cold symptom onset 2
• Ensure adequate intake of all nutrients through a balanced diet first 1

Risk-Benefit Assessment

• Benefits of routine supplementation are questionable for most patients with adequate nutritional status
• Potential risks include:
  • Zinc: Reduced immune function with excessive intake 3
  • Vitamin C: Oxalate toxicity with high doses 3

Special Considerations

Malnourished Patients

• Screen for malnutrition risk in patients with viral infections 1
• For malnourished patients, ensure provision of daily allowances (not megadoses) of vitamins and trace elements 2

Common Cold Specific Recommendations

• For common cold, zinc lozenges (≥75 mg/day) started within 24 hours may be beneficial 2
• Individual testing of therapeutic vitamin C may be worthwhile for common cold patients given its low cost and safety 2

While some research suggests potential benefits of combined zinc and vitamin C supplementation for symptom relief in common cold 4, the highest quality and most recent clinical guidelines do not support routine supplementation with supraphysiologic doses during active viral infections unless there is a proven deficiency.