Antioxidants

Alpha-Lipoic Acid (ALA)

Also known as: Thioctic acid, R-lipoic acid, Lipoic acid

The universal antioxidant — fat- and water-soluble, with genuine trial data for diabetic neuropathy and skin aging.

By IngredientWiki Editorial Team
Fact-checked by IngredientWiki Editorial Team
Updated 2026-09-26
3 min read

In short

Alpha-lipoic acid (ALA) is a naturally occurring compound with an unusual résumé among antioxidants: it is soluble in both fat and water, which lets it work throughout cells and recycle other antioxidants like vitamins C and E. Its strongest clinical credential is diabetic neuropathy — oral and intravenous ALA significantly reduce burning and tingling pain in trials, and it is a prescription neuropathy treatment in Germany. It also has a real if modest evidence base in skin anti-aging, where topical ALA smooths texture. The caveat: typical oral ALA is absorbed erratically, and benefits require weeks of consistent dosing.

Fat- and water-soluble — the 'universal antioxidant'
Recycles vitamin C, vitamin E, and glutathione
Trial-backed for diabetic neuropathy pain (oral + IV)
Topical ALA has genuine anti-aging data

What is Alpha-Lipoic Acid (ALA)?

Alpha-lipoic acid earns the 'universal antioxidant' title the way few supplements do — by actually qualifying. Most antioxidants are confined to one compartment of the cell; ALA works in both the watery cytoplasm and the fatty membranes, and its reduced form actively regenerates spent vitamin C and E, making it a hub in the antioxidant network rather than just a scavenger. That mechanistic depth has translated into one strong clinical use — diabetic neuropathy — and a scattering of smaller but real applications, from skin texture to blood sugar. It is the rare supplement that behaves as advertised, within honest limits.

Where it comes from

Natural sources

Synthesized by the body in mitochondria, where it is an essential enzyme cofactor
Food sources: spinach, broccoli, organ meats, potatoes — in small amounts
Occurs as two mirror-image forms: R- (natural) and S- (synthetic)

How it's made

Supplements use racemic (R+S) ALA or purified R-ALA; intravenous ALA is used medically in Europe.

What it does in products

Benefits

Diabetic neuropathy

strong evidence

Randomized trials (including the ALADIN and SYDNEY series) show ALA — especially intravenously, and orally at 600 mg — reduces neuropathic burning and numbness in diabetic patients.

Antioxidant support

strong evidence

ALA measurably raises antioxidant capacity and reduces oxidative stress markers in trials — a hub role in cellular defense.

Skin anti-aging (topical)

moderate evidence

Human studies find topical ALA improves skin roughness and fine lines and reduces sun-related damage markers.

Insulin sensitivity

moderate evidence

Some trials report improved insulin sensitivity and glucose handling, though results are mixed and modest.

Side effects & safety

Nausea or stomach upset (uncommon)Take with food; starting at lower doses helps.

Skin rash (rare)Discontinue if it appears.

Safety considerations

Insufficient safety data in pregnancy — avoid supplements.
May add to blood-sugar-lowering effects of diabetes medications — monitor glucose.
Theoretical reduction of thyroid hormone effectiveness — separate dosing.
Not for: Known allergy
Not for: Thiamine deficiency (ALA can worsen symptoms unless corrected first)

How it's used

In supplements

Neuropathy and general use: 300–600 mg daily, with food, for at least 4–6 weeks. R-ALA is used at roughly half the racemic dose. Topical products use 1–5% ALA.

Regulatory status

Dietary supplement under DSHEA in the US; intravenous ALA is an approved neuropathy treatment in Germany.
GRAS (generally recognized as safe) for food use.

R vs S: the chirality question

ALA exists in two mirror-image forms, and they are not equal: R-ALA is the biologically active, naturally occurring enantiomer, while S-ALA is its synthetic mirror with far weaker activity. Standard 'alpha-lipoic acid' supplements are racemic — a 50:50 R/S mixture — so a 600 mg capsule delivers 300 mg of the active form. Purified R-ALA costs more and is used at lower doses on the theory that only the active half matters. The clinical trials that established ALA's benefits mostly used racemic product, so the practical evidence base is racemic; the R-only products are pharmacologically cleaner but less directly trial-matched. Either is defensible.

Frequently asked questions

Does alpha-lipoic acid help nerve pain?

In diabetic neuropathy, yes — the trial evidence is among the best for any supplement, especially intravenous therapy and oral 600 mg dosing over weeks. For other neuropathy causes, evidence is thinner.

What is the best time to take alpha-lipoic acid?

With a meal, ideally 30 minutes before, once daily. Consistency over 4–6+ weeks matters more than timing precision, and food reduces the stomach upset some people experience.

Can I use alpha-lipoic acid on my skin?

Topical ALA (1–5%) has real data for texture and fine lines, though its instability makes formulation tricky — look for stabilized serums and use them at night. Some users notice a brief warming sensation.

The bottom line

Alpha-lipoic acid is a credible multi-role antioxidant: the supplement with the strongest neuropathy data outside pharmaceuticals, a genuine cellular antioxidant hub, and a modestly supported skin active. Use 300–600 mg daily with food, and give it weeks to work.

References

Alpha-lipoic acid and diabetic neuropathy — literature search. PubMed (National Library of Medicine). https://pubmed.ncbi.nlm.nih.gov/?term=alpha+lipoic+acid+diabetic+neuropathy+randomized
Alpha-lipoic acid and skin aging — literature search. PubMed (National Library of Medicine). https://pubmed.ncbi.nlm.nih.gov/?term=alpha+lipoic+acid+skin+aging
Alpha-lipoic acid and glucose metabolism — literature search. PubMed (National Library of Medicine). https://pubmed.ncbi.nlm.nih.gov/?term=alpha+lipoic+acid+insulin+sensitivity
Alpha-lipoic acid compound summary. PubChem (National Library of Medicine). https://pubchem.ncbi.nlm.nih.gov/compound/6112