R-Lipoic acid (R-ALA, natural enantiomer, free acid) vs. Racemic alpha-lipoic acid (R,S / DL / thioctic acid)
Among 307 on-market alpha-lipoic acid products with an identifiable primary form, 61.6% use R-Lipoic acid (R-ALA, natural enantiomer, free acid) (189 products) and 20.5% use Racemic alpha-lipoic acid (R,S / DL / thioctic acid) (63).
| R-Lipoic acid (R-ALA, natural enantiomer, free acid) | Racemic alpha-lipoic acid (R,S / DL / thioctic acid) | |
|---|---|---|
| Quality tier | Unrated | Unrated |
| Alpha-Lipoic Acid by weight | — | — |
| Share of market | 61.6% | 20.5% |
| On-market products | 189 | 63 |
| Median declared dose | 100 mg middle half: 50–150 | 120 mg middle half: 50–300 |
| Most common brands | BulkSupplements.com, Life Extension, NFH | Pure Encapsulations, Genestra Brands, Bluebonnet |
Doses are declared per serving in mg. “By weight” is the share of the ingredient that is the nutrient itself (e.g. elemental magnesium in a magnesium salt).
Why R-Lipoic acid (R-ALA, natural enantiomer, free acid) is unrated
The naturally occurring enantiomer; the free acid is described as unstable/poorly soluble. In one randomized crossover (n=20, progressive MS), 600 mg R-LA was bioequivalent in R-LA AUC/Cmax to 1,200 mg racemic R,S-LA and caused fewer GI side effects (Cameron 2020); a pilot (Keith 2012) found variable, age-dependent differences. No outcome trial compares them, so it is not ranked.
Source: Cameron M et al. 2020, J Clin Pharmacol 60(8):1099-1106, PMID 32212340; Keith DJ et al. 2012, Pharmacol Res 66(3):199-206, PMID 22609537; Carlson DA et al. 2007, Altern Med Rev 12(4):343-351, PMID 18069903 (background statement; study itself tested the sodium salt)
Why Racemic alpha-lipoic acid (R,S / DL / thioctic acid) is unrated
Equal mix of the natural R and the S enantiomer. Human comparisons with R-ALA are small: in a randomized crossover in 20 people with progressive MS, 600 mg R-LA gave R-LA AUC and Cmax bioequivalent to 1,200 mg racemic R,S-LA with fewer GI side effects (Cameron 2020); a pilot found variable, age-dependent differences (Keith 2012). No outcome trial compares the forms, so it is not ranked. The pharmaceutical (thioctic acid) tablet form also has PK data (Hermann 2014).
Source: Hermann R et al. 2014, Clin Pharmacol 6:195-204, PMID 25506250; Cameron M et al. 2020, J Clin Pharmacol 60(8):1099-1106, PMID 32212340; Keith DJ et al. 2012, Pharmacol Res 66(3):199-206, PMID 22609537