Do you take supplements in the winter?
A good Probiotic- Water Keifer or Kombucha are good options
Vitamin D3 with Vitamin K2. The sunlight grows scarce in the long dark winter days. Dr. Michael Holick estimates that 50% of the general population is Vitamin D deficient. Remember to take Vitamin K2 and Magnesium with your Vitamin D3. Vitamin D3 is fat soluble, so taking some form of healthy fat with it will help optimize absorption.