If I recall, the natural flavor comes from wild yams. It's hard to imagine the few drops you hold in your mouth being enough to do you damage. Personally I wouldn't worry about health supplements. That's not where the big bad carb crocodile lives.
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"Nothing in the world can take the place of persistence. Talent will not; nothing is more common than unsuccessful men with talent. Genius will not; unrewarded genius is almost a proverb. Education will not; the world is full of educated derelicts. Persistence and determination are omnipotent."
-Calvin Coolidge