Alpha-lipoic acid

What it is

Alpha-lipoic acid (ALA) is a sulphur-containing compound your cells make and use in energy metabolism. It is also found in small amounts in foods such as spinach, broccoli and red meat.

Supplements are used for their antioxidant activity and in some countries (notably Germany) as a treatment for diabetic nerve pain. In the UK it is sold as a food supplement.

It comes as two mirror-image forms, R and S. The R form is the one made naturally in the body.

How it works

ALA acts as a cofactor in mitochondrial enzymes that turn food into energy. It is also an antioxidant that works in both water and fat, and can help regenerate other antioxidants such as vitamin C and glutathione. It may improve how cells respond to insulin.

What the evidence says

• Moderate Symptoms of diabetic neuropathy
  Studies, mostly using intravenous or around 600 mg oral doses, suggest some symptom relief; it is not a substitute for managing diabetes.
• Limited Blood sugar and insulin sensitivity
  Small trials show modest improvements in some people, with inconsistent results.
• Moderate Antioxidant status
  It raises some antioxidant markers, but that does not automatically translate into health benefits.
• Weak Weight loss
  Trials show very small average changes, of doubtful practical importance.
• Weak Slowing ageing
  No convincing human evidence.

Evidence ratings are our plain-English summary of how much good human research exists, not a promise of results. How we rate evidence.

Dosage and timing

• Common supplement doses are 300-600 mg daily, sometimes split into two.
• Taking it on an empty stomach may improve absorption but can upset some stomachs; with food is fine if so.
• R-ALA doses are often about half those of racemic products.
• If you have diabetes, tell your clinician before starting, as dose changes to medicines may be needed.

Forms and what to look for

• Racemic ALA (R plus S mixture) is the cheapest and most used in trials.
• R-ALA is the natural form, often sold as more potent and more expensive; evidence that it is clearly better in practice is limited.
• Sodium R-ALA is a more stable salt version marketed for better absorption.
• Check the label states whether the dose is R-ALA or total ALA.

What to expect, and when

• Effects on blood sugar, if any, may appear over weeks.
• Nerve symptoms in studies were assessed over weeks to months.
• Many people with no specific condition will notice nothing.

Side effects

• Nausea, stomach upset or heartburn.
• Skin rash or itching.
• Dizziness or headache.
• Low blood sugar symptoms (shakiness, sweating) in people on diabetes medicines.
• A sulphur-like odour in urine reported by some.

Interactions

• Diabetes medicines and insulin: ALA can lower blood sugar and increase the risk of hypoglycaemia.
• Thyroid medicines (levothyroxine): ALA might affect thyroid hormone levels; monitoring is wise.
• Chemotherapy: antioxidants may interfere; check with your oncology team.
• Alcohol and low thiamine: ALA is sometimes used in people with heavy drinking, but thiamine status matters; speak to a clinician.

Who should avoid it

• People with diabetes unless supervised by their clinician.
• People with thyroid conditions, unless monitored.
• Pregnant or breastfeeding women, due to limited data.
• People with a thiamine deficiency or heavy alcohol use should get medical advice.
• Anyone with low blood sugar tendencies.

Risks and safety

• Hypoglycaemia is the main practical concern.
• Very rare cases of autoimmune insulin syndrome have been reported, mostly in people with a certain genetic background.
• High doses can cause marked stomach upset.
• Not banned in sport as far as we know, but check current rules.

Buying well: quality and testing

• Choose products stating R-ALA or racemic ALA clearly.
• Prefer brands with third-party testing (USP, NSF or Informed Sport).
• Avoid products mixing ALA with many other ingredients in unknown amounts.
• Check storage instructions, as R-ALA can degrade with heat.

Bottom line

Alpha-lipoic acid has the best evidence for diabetic nerve symptoms and some metabolic markers, and weaker evidence elsewhere. Its blood-sugar effect is a real consideration for anyone on diabetes medicines or thyroid treatment, so those people should speak to a clinician or pharmacist first. For otherwise healthy people, expect modest or no noticeable benefit.