There are several supplements that have shown clinical evidence in helping to prevent or treat the common cold:

1. Zinc:

   • Zinc lozenges containing 10 to 24 mg of zinc gluconate can reduce the duration and severity of the common cold if started within the first 24 to 48 hours of symptoms^1.
   • Regular zinc supplementation might prevent the common cold, although further studies are needed to confirm this^1.

2. Vitamin C:

   • Regular supplementation of Vitamin C (1 to 2 g per day) has been shown to reduce the duration of colds by 8% in adults and 14% in children, as well as decreasing the severity of symptoms^2.

3. Vitamin D:

   • Supplementation with Vitamin D can protect against the common cold, particularly in individuals with baseline deficiencies^2.

4. Echinacea:

   • Prophylactic treatment with Echinacea (2400 mg per day over 4 months) has been found to prevent and treat the common cold^2.

These supplements target various aspects of immune function and adaptive responses, helping the body to fend off infections or reduce their impact.

Would you be interested in specific product recommendations for any of these supplements?