He held up one finger.
"Problem number one. Your bottle says Alpha Lipoic Acid. Not R-Alpha Lipoic Acid. Just 'Alpha Lipoic Acid.'"
He set it on the counter.
"That means it is a fifty-fifty blend. The R form is the one your body makes. The key that fits the lock. The S form is synthetic. Your nerve has never seen it. And it does not just sit there harmlessly. It competes with the R form for the same absorption pathway and blocks it from getting through."
He held up a second finger.
"Problem number two. Even if this were pure R-form, it is in a capsule. Alpha lipoic acid is acidic. Slightly stronger than vinegar. The second this capsule opens in your stomach, the acid goes to work on it."
He tapped the dose on the label. 600mg.
"Oral ALA absorption runs around ten percent in the published data. So out of 600mg, half is the R form. That is 300. Ten percent of that survives your stomach. That is 30 milligrams reaching your bloodstream. Out of 600 on the label."
I stared at him.
"And then," he said, "that 30 milligrams has to travel all the way to the ends of your toes. Through the worst circulation in your entire body. Through capillaries the width of a single human hair."
I asked him what I should do.
"Get the right form. That is step one. Get it past your stomach. That is step two."
He paused.