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Our Members Asked:
I heard the S-form of alpha-lipoic acid is bad for me. Why is it in my supplement?
Reviewed and edited by Tod Cooperman, M.D.
Answer:
The R-form of alpha-lipoic acid is the active, natural form. The S-form occurs when alpha lipoic acid is synthetically manufactured, creating both the S-form and the active R-form. The S-form is most likely inactive, although some information suggests it may an analgesic effect. For more information, see the What It Is section of our Alpha Lipoic Acid Supplements Review, which includes our Top Picks.Join today to unlock all member benefits including full access to all CL Answers and over 1,300 reviews.
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Related CL Answers (3)
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Don15207
June 25, 2017"The S-form is most likely inactive..."
This is the first I'm hearing this! Is it definitely true?
I recently bought a lot of regular S-form ALA so this is disappointing to say the least.
ConsumerLab.com
June 25, 2017It would be very unusual to find an S-form only. Are you sure it was not an R-form or a combination of R- and S-?
Don15218
June 28, 2017The product I bought, "Swanson Ultra Alpha Lipoic Acid 300 mg" does not specify either way. Since the "R-form" form is sold as a seperate, much more expensive variety, wouldn't this one be the cheaper "S-form" only, by default? Thanks.
ConsumerLab.com
June 28, 2017Hi Don -- It is most likely a combination of R- and S-. Extremely unlikely it would be S- only.
Don15225
June 28, 2017Perhaps, but in the absence of a specific "mixed R- and S-" label claim -- and, economics being what it is -- wouldn't it make sense for a manufacturer to isolate out expensive R-form during production so it can be used in their specifically labeled "R-" formulation, while leaving the leftover "S-" for the regular (lower grade) unspecified ALA?
Doing so wouldn't violate a labeling claim and improves the bottom line.
Guess only a chemical analysis would tell for sure if this is being done. Future project?
ConsumerLab.com
June 28, 2017Conceivably, but not in practical terms, Don. Making the the mixed form is not the major expense. Separating them is. It's safe to say that if a product doesn't list the form, assume it's the mixed form.
Don15227
June 28, 2017OK then.
Quoting from your original answer:
"The S-form occurs when alpha lipoic acid is synthetically manufactured, creating both the S-form and the active R-form."
What is the ratio of S- to R- resulting from the synthetic manufacture of ALA? If there's not a significant amount of R- and the S- is inactive(?) may have to consider dumping this and purchasing the R- only type.
ConsumerLab.com
June 28, 2017It will be half in the R form and half in the S form, Don.
Don15230
June 29, 2017Thank you. Greatly appreciate the discussion.