Alpha-Lipoic Acid (ALA)

What it is

Alpha-lipoic acid, also called thioctic acid, is a fatty acid with two sulfur atoms in a five-membered ring. Your body produces it itself from octanoic acid and cysteine, and it sits as a tightly bound cofactor in mitochondrial dehydrogenase complexes, that is, right in the middle of energy metabolism. Hardly any is added through food: pork heart contains 1.1 to 1.6 mg per kilogram, veal muscle only 0.07 to 0.15 mg per kilogram.

It was discovered around 90 years ago and entered clinical use at the end of the 1950s. That is why things look different here than with most biohacking substances: there are not just a few pilot studies, but large, properly randomized drug trials spanning decades.

R form or racemate — the difference that is often misrepresented

Alpha-lipoic acid occurs in two mirror-image forms. The R form is the natural one that your body builds and that is found in food; the S form only arises during chemical synthesis. EFSA assumes that industrial production mainly yields the racemate, that is, the mixture of both. The R form is indeed better absorbed: its bioavailability, measured by peak blood concentration, is 40 to 50 percent above that of the S form. In return, it is less stable.

It does not follow, however, that it works better clinically. All of the efficacy evidence comes from trials with the racemate — the SYDNEY trial states this explicitly, and the medicine approved in Germany contains DL-alpha-lipoic acid. There is no trial that tests the R form against the racemate in patients. Anyone advertising R-alpha-lipoic acid with the figures from the neuropathy trials is transferring them to a form in which they were never collected.

How it is supposed to work

The story behind it is that of the universal antioxidant: alpha-lipoic acid scavenges free radicals, binds metal ions and returns other antioxidants to their active state. Because it works in both aqueous and fatty environments, it is said to work everywhere. In diabetic neuropathy, a more concrete argument is added: high blood glucose generates oxidative stress in the nerves and the small vessels that supply them — that is where it is supposed to act.

In humans, the biochemistry is well supported, but the chain of action down to the nerve is not. The plasma half-life is about 30 minutes, and the absolute bioavailability around 30 percent, because the liver extracts much of it directly. Whether this brief rise measurably changes anything in the nerve is the point at which the trials diverge.

Blood glucose, weight and liver

Outside neuropathy, alpha-lipoic acid is advertised mainly for blood glucose and insulin sensitivity. The broadest analysis comprises 41 papers and finds a small effect on long-term blood glucose: HbA1c fell by 0.35 points. On insulin and HOMA-IR, that is, on insulin sensitivity itself, the same analysis found no effect. In polycystic ovary syndrome, HOMA-IR improved across four studies, but with low certainty and 96.32 percent heterogeneity — a signal, not a foundation.

On weight, there is a small but robust effect: 10 double-blind trials showed 1.27 kg more weight loss and 0.43 kg per square meter lower BMI than with placebo. For the liver the finding is negative: seven trials with 414 participants with non-alcoholic fatty liver disease showed no effect on liver enzymes, blood lipids, glucose values or body measurements.

What the studies show

NATHAN 1 — four years, primary endpoint missed

The longest trial of all: 460 people with diabetes and mild to moderate polyneuropathy, 233 on 600 mg orally, 227 on placebo, four years double-blind. The primary endpoint was a composite score of the lower-limb deficit score and seven neurophysiological tests. It was missed; p was 0.105. Secondarily, the Neuropathy Impairment Score improved with p equal to 0.028 and the deficit score with p equal to 0.05. The authors themselves name the reason for the failure: in the placebo group, the main endpoint did not worsen significantly at all — there was nothing to slow down.

SYDNEY 2 — five weeks oral, primary endpoint met

Randomized, double-blind, placebo-controlled, 181 patients, five weeks of oral administration at three dose levels. The primary endpoint was the Total Symptom Score. It fell by 4.9 points or 51 percent on 600 mg, by 4.5 on 1,200 mg and by 4.7 on 1,800 mg, compared with 2.9 points or 32 percent on placebo. The responder rates were 62, 50 and 56 percent compared with 26 percent. Nausea, vomiting and dizziness increased with dose.

ALADIN III — seven months, no difference from placebo

The trial missing from advertising copy: 509 outpatients with type 2 diabetes, three arms of infusion plus oral follow-up treatment, infusion plus placebo, and placebo only. On day 19, the symptom score did not differ significantly: a median decrease of 3.7 points compared with 3.0 on placebo, p equal to 0.447. After seven months, no difference at all could be seen between the groups.

Where the data stop

In almost all trials, the primary endpoint was the Total Symptom Score — a sum of stabbing pain, burning pain, tingling and numbness of the feet. That is a patient report, not a measuring device. This is where the limit of the data lies: what patients feel improves reproducibly. What can be measured with a tuning fork and an electrode remains unchanged — in the meta-analysis of 10 trials, vibration perception, deficit score, pain scale, nerve conduction velocity and sensory nerve action potential showed no significant effect. The only positive long-term finding on nerve conduction comes from ALADIN II and is based on 65 patients who remained after exclusion of widely scattered data.

For metabolically healthy people, the data base is missing entirely: no endpoint trial shows a benefit as an antioxidant or anti-aging agent for people without diabetes. The often-cited recycling of vitamin C, vitamin E and glutathione is biochemically described, but a controlled human study deriving a clinical benefit from it could not be found.

Status, approval and legal

In Germany, alpha-lipoic acid is approved as a medicine. The indication in the package leaflet is abnormal sensations in diabetic nerve damage; the active ingredient is DL-alpha-lipoic acid, that is, the racemate, and the daily dose is 600 mg, on an empty stomach about 30 minutes before the first meal. In parallel, the same substance is sold as a dietary supplement, where manufacturers mostly recommend 300 to 600 mg daily. There are no approved health claims, no binding national maximum amount could be found, and in 2021 EFSA was unable to derive a safe intake level. Since 2015, on the recommendation of the European pharmacovigilance committee, a warning about insulin autoimmune syndrome has been included in the product information. No reliable source on doping relevance could be accessed, so nothing is stated about it here.

Safety

The most common side effects are nausea and dizziness, and they increase with dose. In NATHAN 1, serious adverse events over four years were 38.1 percent compared with 28.0 percent on placebo. Liver damage at usual doses has not been described; overdoses can trigger seizures and multi-organ failure. The most serious known risk is insulin autoimmune syndrome: EFSA evaluated 49 case reports, 41 of them in women, aged between 28 and 82 years, at doses between 200 and 800 mg daily and after 7 to 120 days. In all cases it resolved after stopping. Those affected are carriers of certain HLA variants that cannot be identified without a genetic test: DRB1*04:03 has a prevalence of 0.6 to 1.8 percent in Germany, DRB1*04:06 of 0.1 to 1 percent in Europe. Anyone taking insulin or oral antidiabetic drugs must expect an enhanced lowering of blood glucose. Cisplatin can lose effectiveness; iron, magnesium, calcium-containing preparations and dairy products form complexes. It is not suitable for children or for pregnant and breastfeeding women.

Sources

• Ziegler et al., Diabetologia 1995 (ALADIN)
• Ziegler et al., Diabetes Care 1999 (ALADIN III)
• Ametov et al., Diabetes Care 2003 (SYDNEY)
• Ziegler et al., Diabetic Medicine 2004 (meta-analysis, 4 studies)
• Ziegler et al., Diabetes Care 2006 (SYDNEY 2)
• Ziegler et al., Diabetes Care 2011 (NATHAN 1)
• Mijnhout et al., International Journal of Endocrinology 2012
• Hsieh et al., Nutrients 2023 (meta-analysis, 10 studies)
• EFSA NDA Panel, EFSA Journal 2021 (insulin autoimmune syndrome)
• LiverTox, NIH/NIDDK 2023 (Alpha Lipoic Acid)