Support immune and cellular health with Country Life Quercetin + D3. Quercetin is a beneficial flavonoid found in many fruits, vegetables and grains that has potent antioxidant properties to protect the body from free radicals. Vitamin D is best known for its support of healthy bones, but this vitamin is also key to healthy immune system function. Adequate vitamin D intake ensures the cells in your immune system are primed and ready to respond. Each serving of Country Life Quercetin + D3 delivers 500 mg quercetin and 20 mcg (800 IU) vitamin D to support cellular and immune health.