Tea is probably the best olive leaf supplement, as its action is mild but all of the health benefits are there. The use of organic leaves is probably the better option, as no chemicals are used in their production. The leaves should be dried below 150 degrees Fahrenheit (65 degrees Celsius). All supplements should be checked for production, manufacturing processes, and active ingredients, especially oleuropein.
Tinctures are the best olive leaf supplement to use in cases of viral and bacterial infections, as they are absorbed quickly into the bloodstream via the mucous membranes. Some volatile substances are lost during the drying process necessary in the preparation of capsules, but these are preserved in the cold extraction process used in the making of a tincture. There are no fillers or preservatives used, and a good quality tincture should last about five years. The bitter taste and higher cost may be off-putting for some, however.