Sleep and stressMostly marketing

GABA

Also called: gamma-aminobutyric acid, 4-aminobutanoic acid, fermentation-derived GABA.

A neurotransmitter sold in capsules for sleep, with no demonstration that it reaches the human brain and no sleep claim permitted in Canada.

Stress Sleep

What it is

GABA (gamma-aminobutyric acid) is the brain's main inhibitory neurotransmitter, the one that puts the brakes on neuronal excitation, and the brain makes its own on site. As a supplement, it is produced by bacterial fermentation (Lactobacillus) or by synthesis. People buy it for relaxation, sleep and, at much higher doses, for growth hormone.

What the label does not say

The question of whether it reaches the brain is unsettled. The 2020 systematic review concludes that no data show GABA crossing the blood-brain barrier in humans; the 2015 review judges the mechanism far from clear and raises an indirect route through the gut and the vagus nerve. The GABA in the capsule is not the GABA the brain uses.
Sleep rests on three small studies (10, 16 and 40 people) at 100 to 300 mg for 1 to 4 weeks, with shorter sleep latency and little effect on sleep maintenance; in 11 of the 14 studies in the review, at least one author was employed by an industry company. The authors' verdict: limited evidence for stress, very limited for sleep.
In Canada, the only permitted claim is "helps to temporarily promote relaxation"; no sleep claim is allowed for GABA. A bottle sold for sleep is relying on something other than its monograph.
The doses look nothing alike from one trial to the next: 2 to 100 mg for stress, 100 to 300 mg for sleep, 3 to 5 g for growth hormone, while Health Canada allows up to 3,000 mg per day. The number on the bottle does not say which trial it is imitating.

The forms on the shelf

Fermentation-derived GABA (Lentilactobacillus hilgardii, Levilactobacillus brevis) and seaweed-derived GABA (Laminaria japonica): the three natural sources accepted by Health Canada. The Japanese stress trials used very small doses of fermentation-derived GABA, from 2 to 26 mg.
Synthetic GABA: also accepted. The sleep trials (100 to 300 mg) used biosynthetic GABA.
Growth hormone doses: 3 to 5 g in the trials cited by Examine, nothing like the relaxation capsules.

Published reference values

No recommended intake. Health Canada: 50 to 3,000 mg per day, at most 750 mg per dose; at 300 mg and above, consult beyond 4 weeks and avoid alcohol.
Safety (United States Pharmacopeia review): no serious effect up to 18 g per day for 4 days or at 120 mg per day for 12 weeks; reported effects: abdominal discomfort, headaches, drowsiness, and a transient drop in blood pressure of less than 10%.
Pregnancy and breastfeeding: no studies; the same review calls for caution because GABA acts on neurotransmitters and the endocrine system.

When

The stress trials measure brain waves within the hour after the dose; the sleep trials gave it at bedtime for 1 to 4 weeks.

Keep apart from

Antihypertensives: the United States Pharmacopeia review flags a risk of hypotension when combined.
Alcohol: to be avoided with a product dosed at 300 mg and above per day (Canadian label).

To mention to a professional

Low blood pressure or a blood pressure medication, pregnancy and breastfeeding, use beyond 4 weeks at 300 mg and above: check with a health care professional.

What it is sold for, and what the data show

GABA is sold as the calming neurotransmitter put in a capsule, to help you sleep. The actual data: a few more alpha waves on EEG in small industry studies, three sleep trials totalling 66 people, and no demonstration that it reaches the human brain. Examine writes that the body regulates too well for an oral intake to change its physiology much. The product is safe at the doses sold; it is the shortcut between the brain's molecule and the capsule that does not hold up.

From the plate first

Present in trace amounts in food: the 2015 review calculates that it would take 2.34 kg of raw spinach to swallow 100 mg.

Sources

Educational information, drawn from the sources above. It does not replace the advice of a health professional, who remains the reference for your situation, your medications, pregnancy or breastfeeding.