Supplements and Herbs to Reduce Cortisol and Stress, Ranked by the Trials
The supplements with the best evidence for lowering cortisol are ashwagandha, phosphatidylserine and omega-3 fish oil, with rhodiola, L-theanine and magnesium close behind for the stress symptoms that go with a high cortisol load. Ashwagandha has reduced morning serum cortisol by 14 to 28% in several placebo-controlled trials; phosphatidylserine blunts the cortisol spike after exercise and mental stress; and 2.5 g/day of omega-3 lowered cortisol reactivity to a laboratory stressor by 19% in a 2021 trial. Everything else sold as a 'cortisol blocker' sits on thinner ground.
A word on what cortisol actually is. It is not a toxin to be suppressed; it is the hormone that gets you out of bed and keeps your blood pressure up. The problem most people mean by 'high cortisol' is a stress response that will not switch off: poor sleep, belly-weight gain, a wired-but-tired feeling, and a blunted morning peak followed by evening alertness. The supplements below help nudge that pattern back toward normal. They do nothing for genuinely high cortisol from Cushing's syndrome, steroid medication or an adrenal tumour, and they will not fix cortisol that is high because you sleep five hours and drink six coffees.
This guide is for adults with chronic stress and the symptoms above. See a doctor instead if you have rapid weight gain in the face and trunk with thin limbs, purple stretch marks, easy bruising, new high blood pressure or diabetes (possible Cushing's), or if stress has tipped into depression, panic or using alcohol to cope. Ask for a morning cortisol or a late-night salivary cortisol if you want a number rather than a guess.
Quick answer
- Ashwagandha — lowered serum cortisol by 14–28% in three placebo-controlled RCTs at 240–600 mg/day
- Phosphatidylserine — 400–800 mg/day blunts the cortisol rise after mental and physical stress
- Omega-3 (EPA/DHA) — 2.5 g/day cut cortisol reactivity to a lab stressor by 19% over 4 months
- Rhodiola rosea — reduced the cortisol awakening response and burnout symptoms in a 28-day RCT
- L-theanine — lowers salivary cortisol and heart rate within an hour of a stressful task
- Magnesium — low magnesium raises stress hormones; replacing it lowers subjective stress in deficient people
The 10 best herbs and supplements for stress and cortisol
Ranked by the strength of human evidence. Strong = multiple trials or a meta-analysis. Moderate = a few small trials. Preliminary = early or animal data.
In a 60-day RCT of 64 chronically stressed adults, 600 mg/day of root extract cut serum cortisol by 27.9% versus 7.9% on placebo and reduced perceived stress scores by 44%. A 2019 RCT in 60 adults found 240 mg/day lowered morning cortisol by 23% and DHEA-S levels improved, and a third trial found 250 mg and 600 mg both reduced cortisol with the higher dose working better. It is the only herb with multiple placebo-controlled trials where cortisol itself, not just a questionnaire, moved.
- Key evidence
- 2012 RCT (Chandrasekhar), 2019 RCT (Lopresti) and 2019 dose-ranging RCT (Salve)
- Studied dose
- 300–600 mg/day of a root extract standardised to withanolides (KSM-66 or Sensoril), for 8 weeks; morning or split
- Best for
- Chronic stress with poor sleep, anxiety and a wired-but-tired pattern
- Cautions
- Can raise thyroid hormone levels; monitor with levothyroxine or hyperthyroidism. Rare liver injury reports: stop if you develop nausea, dark urine or jaundice. Avoid in pregnancy, and stop 2 weeks before surgery. May add to sedatives.
Phosphatidylserine
Moderate evidencePhosphatidylserine (PS) dampens the brain's ACTH signal to the adrenals. A 2008 RCT found 600 mg/day for 10 days reduced the cortisol response to intense cycling by about 30% compared with placebo, and a 2004 trial of a PS–phosphatidic acid complex (400 mg) blunted the ACTH and cortisol response to a laboratory stress test in chronically stressed adults, with the effect strongest in those who were most stressed. A 2014 follow-up confirmed the 400 mg dose worked while 200 mg and 800 mg did not, a curious dose curve that still needs replicating.
- Key evidence
- 2004 and 2014 placebo-controlled stress-test RCTs (Hellhammer) and 2008 exercise RCT (Starks)
- Studied dose
- 400–600 mg/day of soy- or sunflower-derived phosphatidylserine (or 400 mg of a PS–PA complex), for 2–6 weeks
- Best for
- Over-trained athletes, people with an exaggerated stress response, and evening cortisol that keeps you awake
- Cautions
- Mild antiplatelet effect: tell your doctor if you take warfarin or antiplatelet drugs. Can cause insomnia or stomach upset at high doses. Choose plant-derived PS; bovine-brain PS is no longer sold for prion reasons.
Omega-3 (EPA and DHA)
Moderate evidenceA 4-month RCT of 138 sedentary, overweight middle-aged adults found 2.5 g/day of omega-3 reduced the cortisol response to a laboratory stressor by 19% and reduced the inflammatory IL-6 response by 33% compared with placebo, and slowed a marker of cellular ageing. A smaller 2003 trial in healthy men found 7.2 g/day of fish oil for 3 weeks blunted the adrenaline and cortisol rise to mental stress. Omega-3 also has a meta-analysis-level evidence base for depression and anxiety symptoms, which are the usual companions of chronic stress.
- Key evidence
- 2021 RCT (Madison, Kiecolt-Glaser), 138 participants, 4 months
- Studied dose
- 1–2.5 g/day of combined EPA and DHA from fish oil, with a meal, for at least 8–16 weeks
- Best for
- Stress with low mood, inflammation, high triglycerides or a diet low in oily fish
- Cautions
- Doses above 3 g/day increase bleeding risk; discuss with your doctor if you take anticoagulants or antiplatelet drugs or before surgery. High-dose omega-3 slightly raises the risk of atrial fibrillation in people with heart disease. Choose a third-party-tested product to avoid oxidised oil.
A 28-day placebo-controlled RCT in 60 people with stress-related fatigue (burnout) found 576 mg/day of the SHR-5 extract reduced the cortisol awakening response and improved attention and fatigue scores versus placebo. A 2018 review of 11 trials concluded rhodiola reliably improves stress symptoms, fatigue and mental performance, with two trials showing cortisol changes. It acts fast: a 2012 open study found stress symptoms improved within 3 days of starting 400 mg/day. The trials are small and the extract quality varies enormously between products.
- Key evidence
- 2009 placebo-controlled RCT in burnout (Olsson), 60 participants
- Studied dose
- 200–600 mg/day of a root extract standardised to 3% rosavins and 1% salidroside, in the morning or before lunch
- Best for
- Burnout, stress with exhaustion and poor concentration, long working weeks
- Cautions
- Stimulating: can cause jitteriness and insomnia if taken after mid-afternoon. Possible interactions with SSRIs, MAOIs, and blood-pressure and diabetes drugs. Avoid in bipolar disorder.
L-theanine
Moderate evidenceA 2007 placebo-controlled study found 200 mg of L-theanine taken before a mental arithmetic stress task reduced heart rate and salivary immunoglobulin A responses, and a 2016 trial found 200 mg lowered salivary cortisol and subjective stress about 1–3 hours after a multitasking test. A 4-week RCT in 2019 found 200 mg/day reduced stress-related symptoms and improved sleep quality. It works within the hour and does not make you drowsy, which makes it the right pick for acute, predictable stress.
- Key evidence
- 2016 placebo-controlled stress-task RCT (White) and 2019 4-week RCT (Hidese)
- Studied dose
- 200 mg as needed 30–60 minutes before a stressful event, or 200 mg once or twice daily
- Best for
- Presentations, exams, high-pressure meetings, and offsetting caffeine jitters
- Cautions
- Very few side effects. May slightly lower blood pressure; monitor if you take antihypertensives. Not well studied in pregnancy.
Magnesium glycinate
Moderate evidenceStress raises magnesium loss in urine, and low magnesium amplifies the stress hormone response: a vicious circle described in a 2020 review. A 2017 systematic review of 18 studies found magnesium supplementation reduced subjective anxiety and stress, mostly in people with low intake, and an 8-week trial of 264 stressed adults with low magnesium found 300 mg/day reduced stress scores by about 40%, with vitamin B6 adding a little extra in the most stressed. The effect depends on being low to begin with, which most people on Western diets are.
- Key evidence
- 2018 RCT of magnesium with or without B6 in stressed adults (Pouteau), 264 participants
- Studied dose
- 200–400 mg elemental magnesium/day as glycinate, with the evening meal, for 8 weeks
- Best for
- Stress with muscle tension, headaches, cramps, poor sleep or a diet low in greens and nuts
- Cautions
- Loosens stools at high doses. Separate from tetracycline and quinolone antibiotics by 2–4 hours. Needs supervision in kidney disease.
A 6-week double-blind RCT in 150 adults with symptomatic stress found 1,200 mg/day of holy basil extract improved a composite stress-symptom score about 1.6 times more than placebo, with 39% greater improvement overall. An 8-week 2022 RCT in 100 stressed adults found 125 mg twice daily of a standardised extract lowered hair cortisol (a 3-month average) and improved sleep and stress scores versus placebo. A 2017 review of 24 human trials found universally positive results, which suggests the smaller, open-label studies should be discounted.
- Key evidence
- 2022 placebo-controlled RCT with hair cortisol (Lopresti), 100 participants
- Studied dose
- 250–1,200 mg/day of a leaf extract, or 2–3 cups of tulsi tea, for 6–8 weeks
- Best for
- Stress with blood-sugar swings, afternoon crashes and mild anxiety
- Cautions
- Lowers blood glucose; monitor with diabetes medication. Mild antiplatelet effect, so stop 2 weeks before surgery and discuss with your doctor on anticoagulants. Avoid in pregnancy and when trying to conceive.
Ginseng's evidence is stronger for fatigue and mental performance under stress than for cortisol itself. A 2013 RCT in 90 adults with chronic fatigue found 2 g/day reduced fatigue scores and oxidative stress markers, and a 2018 systematic review of 10 trials found a modest, consistent benefit for fatigue. Studies measuring cortisol are mixed: one 2010 trial found no change, while animal work shows adaptogenic effects on the HPA axis. It is a reasonable pick when stress is leaving you flat rather than anxious.
- Key evidence
- 2018 systematic review of 10 RCTs for fatigue (Arring)
- Studied dose
- 200–400 mg/day of a root extract standardised to 4–7% ginsenosides (or 1–2 g dried root), in the morning, for 4–12 weeks with a 2-week break
- Best for
- Stress with fatigue, low motivation and brain fog
- Cautions
- Can lower blood glucose and interacts with warfarin (reduced INR). Stimulating: avoid late in the day and with high caffeine intake. May raise blood pressure in some people. Avoid in hormone-sensitive conditions and pregnancy.
The original 'adaptogen', studied extensively in Soviet-era trials that are mostly unavailable in English. Modern evidence is thin: a 2004 RCT in 96 people with chronic fatigue found no overall benefit but improvement in a subgroup with milder fatigue, and small studies report better endurance and immune markers under physical stress. One 2013 study found a 2-month course of eleuthero and rhodiola improved stress and cognitive scores. Preliminary at best, included because it is widely sold and relatively safe.
- Key evidence
- 2004 RCT in chronic fatigue (Hartz), 96 participants
- Studied dose
- 300–1,200 mg/day of a root extract standardised to eleutherosides, for 6–8 weeks then a break
- Best for
- Physical stress loads such as heavy training or long shifts, in people who find rhodiola too stimulating
- Cautions
- May raise blood pressure at high doses; avoid with uncontrolled hypertension. Can interact with digoxin (false assay readings) and may affect blood sugar. Not for pregnancy.
Schisandra is an adaptogen in traditional Chinese medicine with promising animal data showing it normalises stress-induced cortisol and corticosterone, and small human trials on physical and mental performance under stress. A 2018 placebo-controlled trial found 1,000 mg/day of schisandra improved exercise tolerance and reduced fatigue, and it appears in combination adaptogen products that have beaten placebo for attention and stress. There is no human trial yet showing a cortisol reduction, so it sits at the bottom of this list.
- Key evidence
- 2010 review of pharmacology and clinical use (Panossian and Wikman)
- Studied dose
- 500–1,500 mg/day of a berry extract standardised to schisandrins, or 1–3 g dried berry, for 4–8 weeks
- Best for
- People who have tried the better-evidenced options and want to experiment
- Cautions
- Induces liver enzymes (CYP3A4) and can change the levels of many drugs, including tacrolimus, some statins and blood-pressure drugs. Avoid in pregnancy (uterine stimulant in traditional use). May worsen reflux.
How to choose
- If you want the one supplement with the most cortisol-specific evidence, take ashwagandha at 300–600 mg/day for 8 weeks and track sleep and stress on a simple 0–10 scale.
- If you are a hard-training athlete or your stress response is exaggerated (racing heart, sweating, long recovery), phosphatidylserine at 400–600 mg/day is the targeted choice.
- If stress is making you flat, foggy and exhausted rather than wired, pick rhodiola (morning) or panax ginseng; if it is making you anxious and sleepless, pick ashwagandha, L-theanine or magnesium instead.
- If you eat little oily fish, omega-3 at 1–2.5 g/day is a low-risk foundation that also helps mood; it takes 2–4 months, so start it alongside a faster-acting option.
- For a known stressful event, 200 mg L-theanine an hour beforehand is the only pick here that works the same day.
- Do not combine three adaptogens. Pair at most one adaptogen (ashwagandha or rhodiola) with one nutrient (magnesium or omega-3), and give the combination 8 weeks before changing it.
What to skip
'Adrenal support' glandulars and adrenal fatigue formulas
Adrenal fatigue is not a recognised diagnosis (a 2016 systematic review of 58 studies found no evidence for it), and desiccated adrenal products have been found to contain actual steroid hormones, which suppress your own cortisol output. Avoid them.
Cortisol blocker fat-burners (often based on Relora or cissus)
The idea that lowering cortisol melts belly fat comes from one small industry-funded trial of magnolia–phellodendron (Relora) that found a 0.5 kg difference. Nothing sold as a 'cortisol blocker' has shown meaningful weight loss in an independent trial.
Licorice root for stress
Licorice blocks the enzyme that breaks cortisol down, so it raises cortisol activity in tissues, lowers potassium and pushes blood pressure up. It is the wrong direction entirely for someone worried about high cortisol.
Vitamin C megadoses
A single 2001 study found 3 g/day of vitamin C blunted the cortisol response to a stress test, but it has never been replicated at a meaningful scale and doses that high cause diarrhoea and kidney stones in susceptible people. A normal intake from food is enough.
Safety and when to see a clinician
- See a clinician if you have signs of genuinely high cortisol (rounded face, central weight gain with thin arms and legs, purple stretch marks, easy bruising, new high blood pressure or high blood sugar), or if stress has become depression, panic, or dependence on alcohol or sleeping pills.
- Adaptogens interact with thyroid medication (ashwagandha raises thyroid hormone), diabetes drugs (holy basil, ginseng and rhodiola lower glucose) and blood-pressure drugs (eleuthero and ginseng can raise pressure; rhodiola and theanine can lower it). Tell your prescriber before starting.
- Blood thinners: omega-3 above 3 g/day, phosphatidylserine, holy basil and ginseng all affect clotting. Discuss them if you take warfarin, DOACs or antiplatelet drugs, and stop them 2 weeks before surgery.
- Serotonergic drugs: rhodiola and, in theory, ashwagandha and ginseng may interact with SSRIs, SNRIs and MAOIs. Do not stop an antidepressant to start a herb, and do not add one without telling your prescriber.
- Schisandra and St John's wort induce liver enzymes and can lower the levels of many medications, including immunosuppressants, contraceptives and some statins.
- Pregnancy: none of these has adequate safety data, and ashwagandha, holy basil, schisandra and ginseng are specifically advised against. Omega-3 and magnesium at normal doses are the exceptions.
What matters as much as any herb
- Sleep is the biggest cortisol lever there is: one week of 5-hour nights raises evening cortisol and insulin resistance measurably, and no supplement on this page can compensate for it.
- Keep caffeine under about 300 mg/day and none after 2 p.m. Caffeine raises cortisol by roughly 30% for a few hours and the effect does not fully disappear with tolerance.
- Moderate exercise lowers resting cortisol over weeks, but very long or very intense sessions raise it; if you are over-trained, swapping one hard session for a walk may do more than phosphatidylserine.
- Ten minutes a day of slow breathing (around 6 breaths per minute) or a mindfulness practice reduces cortisol in meta-analyses with an effect size comparable to the better herbs here, at no cost and with no interactions.
- Alcohol raises cortisol both acutely and the next morning, and fragments sleep; two or more drinks a night will out-run any adaptogen.
Frequently asked questions
What supplements lower cortisol the most?
Ashwagandha has the largest measured effect, with serum cortisol falling 14–28% in placebo-controlled trials at 240–600 mg/day over 8 weeks. Phosphatidylserine has the best evidence for blunting acute cortisol spikes, and omega-3 at 2.5 g/day lowered cortisol reactivity by 19% over 4 months. Most other products have questionnaire data only.
How long does it take for cortisol supplements to work?
L-theanine works within an hour and rhodiola within days. Ashwagandha trials showed significant cortisol changes at 8 weeks, with stress scores improving from about week 2 to 4. Omega-3 needs 2 to 4 months to change cell membranes. If nothing has shifted after 8 weeks at a studied dose, change approach.
Does ashwagandha really lower cortisol?
Yes, in at least three placebo-controlled trials it lowered serum cortisol by 14–28%. The trials are small (60–64 people) and mostly funded by extract manufacturers, so the true effect may be smaller, but it has been reproduced with different extracts and doses. It also improved sleep and anxiety scores in those trials.
What are the symptoms of high cortisol?
From chronic stress: poor sleep (especially waking at 3–4 a.m.), feeling wired but tired, cravings, weight gain around the middle, frequent colds, and anxiety. From a medical cause such as Cushing's syndrome: a rounded face, purple stretch marks, easy bruising, muscle weakness and high blood pressure. The second set needs a doctor, not a supplement.
Can I test my cortisol at home?
Salivary cortisol kits that sample four times a day give a reasonable picture of your daily rhythm, and a late-night salivary cortisol is one of the standard screening tests for Cushing's. A single morning blood cortisol is less useful because it varies so much day to day. Hair cortisol, used in recent trials, gives a 3-month average but is mostly a research tool.
Which adaptogen is best for stress?
Ashwagandha if stress makes you anxious and sleepless; rhodiola if it makes you exhausted and foggy. They have the most trial evidence of any adaptogens. Holy basil is a reasonable third choice with a recent hair-cortisol trial, while eleuthero and schisandra remain mostly traditional-use picks.
Does magnesium reduce cortisol?
Indirectly. Low magnesium increases the stress hormone response and stress depletes magnesium, so replacing it in people who are low reduces stress scores and improves sleep. In people who already have adequate magnesium, extra does little. Glycinate or citrate at 200–400 mg/day is the sensible form and dose.
References
- Chandrasekhar K, Kapoor J, Anishetty S. A prospective, randomized double-blind, placebo-controlled study of safety and efficacy of a high-concentration full-spectrum extract of ashwagandha root in reducing stress and anxiety in adults. Indian Journal of Psychological Medicine (2012)View source
- Lopresti AL, Smith SJ, Malvi H, Kodgule R. An investigation into the stress-relieving and pharmacological actions of an ashwagandha (Withania somnifera) extract: a randomized, double-blind, placebo-controlled study. Medicine (Baltimore) (2019)View source
- Salve J, Pate S, Debnath K, Langade D. Adaptogenic and anxiolytic effects of ashwagandha root extract in healthy adults: a double-blind, randomized, placebo-controlled clinical study (2019)View source
- Olsson EM, von Schéele B, Panossian AG. A randomised, double-blind, placebo-controlled, parallel-group study of the standardised extract SHR-5 of the roots of Rhodiola rosea in the treatment of subjects with stress-related fatigue. Planta Medica (2009)View source
- Anghelescu IG, Edwards D, Seifritz E, Kasper S. Stress management and the role of Rhodiola rosea: a review. International Journal of Psychiatry in Clinical Practice (2018)View source
- Hellhammer J, Fries E, Buss C, et al.. Effects of soy lecithin phosphatidic acid and phosphatidylserine complex (PAS) on the endocrine and psychological responses to mental stress. Stress (2004)View source
- Starks MA, Starks SL, Kingsley M, Purpura M, Jäger R. The effects of phosphatidylserine on endocrine response to moderate intensity exercise. Journal of the International Society of Sports Nutrition (2008)View source
- Madison AA, Belury MA, Andridge R, et al.. Omega-3 supplementation and stress reactivity of cellular aging biomarkers: an ancillary substudy of a randomized, controlled trial in midlife adults. Molecular Psychiatry (2021)View source
- Kimura K, Ozeki M, Juneja LR, Ohira H. L-Theanine reduces psychological and physiological stress responses. Biological Psychology (2007)View source
- Pickering G, Mazur A, Trousselard M, et al.. Magnesium status and stress: the vicious circle concept revisited. Nutrients (2020)View source
- Jamshidi N, Cohen MM. The clinical efficacy and safety of tulsi in humans: a systematic review of the literature. Evidence-Based Complementary and Alternative Medicine (2017)View source
- Cadegiani FA, Kater CE. Adrenal fatigue does not exist: a systematic review. BMC Endocrine Disorders (2016)View source
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Ask about stress and cortisolThis guide is educational and is not medical advice. Herbs and supplements can interact with prescription medicines and are not regulated like drugs. Talk with a clinician or pharmacist before starting anything new, especially if you are pregnant, breastfeeding, have a chronic condition, or take medication.