3 human trials reported calmer stress responses with lysine, and 2 of them gave it alongside an equal dose of arginine. That pairing is the detail most pages leave out.
It matters most to people who also get cold sores, since arginine is the amino acid that advice tells them to avoid.
Quick Answer: Does Lysine Help Anxiety?
Possibly, but lysine alone is barely tested. A 2004 trial of lysine-fortified wheat lowered trait anxiety in men in Syria. Trials in 2005 and 2007 gave lysine with an equal dose of arginine, 2.64 to 3 g of each, and found lower anxiety or changed stress hormones. 0 trials studied an anxiety disorder.
Key Takeaways
- Lysine-fortified wheat lowered trait anxiety in Syrian men over 3 months.
- 2 trials paired lysine with an equal dose of arginine.
- In Japan, 2.64 g of each for 1 week lowered anxiety scores.
- Rat work used 1 g per kg, or 70 g for an adult.
- 0 trials tested lysine alone in people with an anxiety disorder.
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Where the Anxiety Idea Came From
The idea began in rats, well away from the main uses of lysine, and the doses there were large.
- 2002: A lysine-deficient diet raised stress-induced anxiety in rats.
- 2003: Lysine acted like a partial blocker of serotonin receptor 4.
- Binding: It inhibited 9.17% of serotonin binding in a lab assay.
- Dose in rats: 1 g per kg of body weight, by mouth.
The deficiency study ran for 4 days.[1]Dietary L-lysine deficiency increases stress-induced anxiety and fecal excretion in rats — Journal of Nutrition (2002) View source The receptor study blocked anxiety induced by a serotonin receptor 4 agonist.[2]L-Lysine acts like a partial serotonin receptor 4 antagonist and inhibits serotonin-mediated intestinal pathologies and anxiety in rats — Proceedings of the National Academy of Sciences (2003) View source
The Human Trials
Four randomized human trials touched anxiety or stress, in very different settings.
| Trial | What people took | Who | Finding |
|---|---|---|---|
| Syria, 2004 | Wheat flour fortified with lysine, 3 months | Families on wheat-based diets | Lower trait anxiety in men; smaller cortisol response in women |
| 2005 | 3 g lysine plus 3 g arginine, 10 days | 29 adults with high trait anxiety | Hormone responses to a public speech changed |
| Japan, 2007 | 2.64 g lysine plus 2.64 g arginine, 1 week | 108 healthy adults | Lower trait and state anxiety; lower basal cortisol in men |
| Ghana, 2010 | 1 g lysine a day | 271 adults and children | Fewer illness days; no anxiety result in the abstract |
The Syrian trial fortified wheat for families on cereal diets.[3]Lysine fortification reduces anxiety and lessens stress in family members in economically weak communities in Northwest Syria — Proceedings of the National Academy of Sciences (2004) View source The 2005 trial measured hormones during a public speech.[4]Subchronic treatment with amino acid mixture of L-lysine and L-arginine modifies neuroendocrine activation during psychosocial stress — Nutritional Neuroscience (2005) View source
The 2007 trial was placebo-controlled, in 108 adults.[5]Oral treatment with L-lysine and L-arginine reduces anxiety and basal cortisol levels in healthy humans — Biomedical Research (2007) View source Ghana listed anxiety as an outcome.[6]Effect of lysine supplementation on health and morbidity in subjects belonging to poor peri-urban households in Accra, Ghana — American Journal of Clinical Nutrition (2010) View source Two of the 4 run into the arginine question for cold sores.
The Arginine Catch
Both modern supplement trials gave lysine and arginine together, so neither isolates lysine.
- 2005: 3 g of each, for 10 days.
- 2007: 2.64 g of each, for 1 week.
- Lysine alone: Tested only in the Syria and Ghana trials.
- Cold sore advice: Usually says to avoid arginine.
Who Was Studied
The settings shape what the results can mean for a well-fed adult.
- Syria: Families on wheat-based diets, likely short of lysine.
- Ghana: Households where many were at risk of low intake.
- Japan: Healthy adults, without an anxiety diagnosis.
- 2005: Healthy adults with high trait anxiety scores.
For a well-fed adult, our own lysine capsules supply 1000 mg each with no arginine, a combination no anxiety trial used.
Cortisol and Sleep
Cortisol moved in 2 trials, in opposite directions, and sleep was not measured.
- 2007: Basal salivary cortisol fell in men.
- 2005: Cortisol during stress rose, read as normalisation.
- Syria: Women's cortisol response to a blood draw was smaller.
- Sleep: 0 trials measured it.
Safety If You Try It
The trial doses of 2.64 to 3 g sit under the 6,000 mg provisional level from a 2019 review.[7]Safety assessment of L-lysine oral intake: a systematic review — Amino Acids (2019) View source
- Anxiety medicines: 0 interaction studies with lysine.
- Kidney disease: Untested, so ask first.
- Diagnosed anxiety: Not a substitute for treatment.
- Stomach upset: The most common side effect.
The full list is in who should not take lysine.
Speak to a Clinician Before Taking Lysine If
- You have kidney disease, or have ever been told your kidney function is reduced
- You are pregnant or breastfeeding; we found 0 trials of lysine supplements in pregnancy
- You take high-dose calcium, or an aminoglycoside antibiotic such as gentamicin
- Your cold sores are frequent, severe, near the eye, or you are immunocompromised
- You have gallbladder or heart disease, which one review flags as a theoretical concern
Frequently Asked Questions
How much lysine to take for anxiety? +
The 2005 and 2007 trials used 2.64 to 3 g a day, combined with the same amount of arginine, for 1 week to 10 days. The Ghana trial used 1 g a day.
Does lysine make you calm? +
In 1 Japanese trial of 108 adults, 2.64 g of lysine with 2.64 g of arginine lowered anxiety scores within 1 week. Lysine alone is untested in well-fed adults.
Does lysine bring down cortisol? +
In men in the 2007 trial, basal salivary cortisol fell on lysine plus arginine. In the 2005 trial, cortisol during a stress test rose instead.
Does lysine affect sleep? +
We found 0 trials measuring sleep as an outcome of lysine supplements. The anxiety trials measured questionnaires and hormones over 1 week to 3 months.
How long does it take for lysine to kick in? +
In the 2 supplement trials, effects were measured after 7 to 10 days of daily dosing. The Syrian fortification trial ran 3 months.
Can lysine replace anxiety medication? +
No. 0 trials tested lysine in people with a diagnosed anxiety disorder, and none compared it with any medicine.
Is lysine good for stress? +
The evidence is 3 small trials, 2 with arginine. In Syria, lysine-fortified wheat reduced the cortisol response to a blood draw in women.
Why does lysine affect anxiety in rats? +
In 2003 work, lysine partly blocked serotonin receptor 4, inhibiting 9.17% of binding in a lab assay, and reduced anxiety in rats at 1 g per kg.
Does lysine help depression? +
We found 0 human trials of lysine for depression. The 4 trials above measured anxiety, stress hormones or illness.
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