Vitamin D, definitely worth some amount of supplementation this flu season.
The investigators found that daily or weekly supplementation had the greatest benefit for individuals with the most significant vitamin D deficiency (blood levels below 10 mg/dl) — cutting their risk of respiratory infection in half — and that all participants experienced some beneficial effects from regular vitamin D supplementation. Administering occasional high doses of vitamin D did not produce significant benefits.
Vit D is incredibly important.
Yes, being that I live way too far North to get any meaningful vitamin D between the months of November-March, I supplement daily.