What is the best immune booster supplement?

Not proven effective: Many "non-medical" supplements, foods, herbs, and techniques are claimed to "boost" the immune system, but none have been proven effective. The immune system is complex, and "boosting" it to make it act stronger is not always a good thing. In conditions like arthritis, thyroid disease, diabetes type 1, lupus, eczema, etc..., the immune system is over-acting and damaging the patient's own organs.