R-Lipoic acid (R-ALA, natural enantiomer, free acid) vs. Sodium R-lipoate (Na-R-ALA, stabilized R-lipoic 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 17.9% use Sodium R-lipoate (Na-R-ALA, stabilized R-lipoic acid) (55).
| R-Lipoic acid (R-ALA, natural enantiomer, free acid) | Sodium R-lipoate (Na-R-ALA, stabilized R-lipoic acid) | |
|---|---|---|
| Quality tier | Unrated | Unrated |
| Alpha-Lipoic Acid by weight | — | — |
| Share of market | 61.6% | 17.9% |
| On-market products | 189 | 55 |
| Median declared dose | 100 mg middle half: 50–150 | 150 mg middle half: 50–200 |
| Most common brands | BulkSupplements.com, Life Extension, NFH | Blue Star Nutraceuticals, Universal, SuperSmart |
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 Sodium R-lipoate (Na-R-ALA, stabilized R-lipoic acid) is unrated
One small (n=12) PK study, from the lab that had run the earlier preliminary study, reported significantly higher Cmax and AUC and shorter Tmax for the sodium salt than for R-lipoic acid or racemic ALA, but the comparison extends an earlier preliminary study, and no outcome trials exist -- insufficient to rank. Salt weight is ~10% above acid weight; labels usually declare acid equivalents, so amounts are used as declared.
Source: Carlson DA et al. 2007, Altern Med Rev 12(4):343-351, PMID 18069903