Several supplements have evidence supporting their ability to lower cortisol, with ashwagandha carrying the strongest research backing. Others, including phosphatidylserine, rhodiola rosea, magnesium, L-theanine, and omega-3 fatty acids, also show meaningful effects through different mechanisms. The strength of evidence varies, and each works best in specific contexts.
Ashwagandha
Ashwagandha is the most studied supplement for cortisol reduction. Multiple randomized controlled trials have found that it significantly reduces serum cortisol levels compared to placebo, alongside improvements in self-reported stress, anxiety, fatigue, and sleep quality. The effective dose range in clinical trials spans 240 to 1,250 mg per day of root extract, though benefits appear strongest at 500 to 600 mg daily. An international taskforce from the World Federation of Societies of Biological Psychiatry provisionally recommends 300 to 600 mg of root extract per day, standardized to contain 5% withanolides, for generalized anxiety.
One trial found that even a relatively low dose of 225 mg per day of a root and leaf extract lowered saliva cortisol within 30 days. Another trial using 300 mg of a sustained-release root extract over 90 days produced similar cortisol reductions alongside stress relief. If you’re choosing an ashwagandha supplement, look for root extract standardized to withanolide content, as this is what the clinical trials used.
Safety is worth considering. Current evidence supports short-term use of up to three months, but there isn’t enough data to draw conclusions about long-term safety. Side effects can include drowsiness, stomach upset, diarrhea, and vomiting. Rare cases of liver injury have been linked to ashwagandha supplements. You should avoid it during pregnancy, before surgery, or if you have an autoimmune condition, thyroid disorder, or hormone-sensitive prostate cancer. It can also interact with medications for diabetes, high blood pressure, seizures, and thyroid conditions, as well as sedatives and immunosuppressants.
Rhodiola Rosea
Rhodiola rosea is an adaptogenic herb that works by helping your body return to its baseline stress state more efficiently after cortisol spikes. Rhodiola extracts have been shown to reduce elevated cortisol levels and support what researchers call a “balanced stress response,” meaning your body recovers from stress faster rather than staying in a prolonged high-cortisol state.
Effective doses range from 200 to 600 mg per day. The key detail when shopping for rhodiola is standardization: look for extracts containing at least 3% rosavins and 1% salidroside, which are the active compounds. These percentages should be listed on the label. Most well-formulated products follow this ratio because it reflects the natural proportion found in the root itself.
Phosphatidylserine
Phosphatidylserine (PS) is a fat-based molecule found naturally in cell membranes, and it’s particularly useful for blunting cortisol spikes caused by physical exercise. In one controlled trial, participants who took 600 mg of PS daily for 10 days before a cycling test that ramped from moderate to high intensity showed a significantly lower total cortisol response compared to placebo. Testosterone, growth hormone, and lactate levels stayed the same, suggesting PS specifically targets the cortisol pathway rather than broadly dampening the hormonal response to exercise.
This makes phosphatidylserine a better fit for people whose cortisol concerns are tied to intense training or overtraining rather than chronic psychological stress. The 600 mg dose used in exercise studies is higher than what many PS supplements provide, so check the label carefully.
Magnesium
Magnesium helps regulate cortisol by blocking or diminishing the signaling pathways that deliver cortisol to your brain. Many people are mildly deficient in magnesium without knowing it, and that deficiency alone can amplify your stress response. Correcting a shortfall can help level out cortisol output.
The catch is that research on magnesium for cortisol hasn’t coalesced around a specific type or dose. Studies have used different magnesium compounds (glycinate, citrate, oxide, and others), and no single form has been tested consistently enough to be declared superior for stress reduction specifically. That said, magnesium glycinate and magnesium citrate are generally better absorbed than magnesium oxide. Most adults can safely take 200 to 400 mg of elemental magnesium daily through supplements without issue, though higher doses can cause digestive problems.
L-Theanine
L-theanine is an amino acid found naturally in tea leaves. It promotes relaxation by boosting levels of calming brain chemicals, including GABA, dopamine, and serotonin. This shift in brain chemistry indirectly reduces the stress signaling that drives cortisol production. It doesn’t cause drowsiness, which makes it practical for daytime use.
Most healthy adults take between 200 and 500 mg per day, with 200 mg being the most common dose in studies. The upper limit typically recommended is 500 mg daily. Effects are usually noticeable within 30 to 60 minutes. L-theanine is one of the gentler options on this list and works well as a complement to other cortisol-lowering strategies rather than a standalone solution for significantly elevated levels.
Omega-3 Fatty Acids
Omega-3s from fish oil influence cortisol through their anti-inflammatory properties. Here’s the mechanism: during prolonged stress, your body produces inflammatory messenger molecules called cytokines. These cytokines prevent your stress response system from shutting off properly, keeping cortisol elevated even after the stressor has passed. Omega-3 fatty acids are natural regulators of these inflammatory messengers, helping your body’s stress system return to its resting state.
The evidence for omega-3s as a direct cortisol-lowering supplement is more mixed than for ashwagandha or rhodiola. One trial using 2.2 grams of EPA plus 0.44 grams of DHA daily (totaling about 2.6 grams of omega-3s per day) did not find a significant reduction in cortisol for people with chronic psychological stress. Omega-3s likely work better as a supporting factor for overall stress resilience, particularly when inflammation is part of the picture, rather than as a targeted cortisol intervention.
How to Choose the Right One
Your best option depends on what’s driving your cortisol elevation. For general life stress and anxiety, ashwagandha has the most robust evidence and the clearest dosing guidelines. Rhodiola is a strong alternative if you want something that helps you recover from stress more quickly throughout the day. For exercise-related cortisol spikes, phosphatidylserine at 600 mg is the most targeted choice.
If you suspect you’re simply not getting enough magnesium (common signs include muscle cramps, poor sleep, and feeling wired but tired), correcting that deficiency is a logical first step since it supports your entire stress response system. L-theanine is the mildest option and works well layered with other supplements or as a standalone for mild, everyday tension. Omega-3s are worth taking for their broad health benefits but shouldn’t be your primary strategy if lowering cortisol is the specific goal.
Combining supplements is common, but start with one at a time so you can gauge its effect before adding another. Give each supplement at least four to six weeks before evaluating results, since cortisol patterns shift gradually.