Ashwagandha is the most consistently studied supplement for lowering cortisol, with multiple clinical trials showing significant reductions in both blood and saliva cortisol levels compared to placebo. But it’s not the only option worth considering. A handful of other supplements have solid evidence behind them, and the best choice depends on whether your cortisol is chronically elevated from ongoing stress or spiking in response to specific triggers like intense exercise.
How Cortisol Works in Your Body
Cortisol is produced through a chain reaction between three organs: the hypothalamus, pituitary gland, and adrenal glands. When you encounter stress, your hypothalamus sends a chemical signal to your pituitary, which then tells your adrenal glands to release cortisol. Once cortisol levels rise high enough, they signal back to the hypothalamus to shut off the process. This feedback loop is supposed to be self-regulating.
The problem is that chronic stress, poor sleep, and other lifestyle factors can keep this system activated longer than it should be. When cortisol stays elevated for weeks or months, it contributes to weight gain (especially around the midsection), disrupted sleep, brain fog, and weakened immunity. Supplements that lower cortisol generally work by either calming the initial stress signal or helping the feedback loop shut off more efficiently.
Ashwagandha: The Strongest Evidence
Ashwagandha has been tested in more cortisol-focused clinical trials than any other supplement. A review of the evidence by the NIH Office of Dietary Supplements concluded that ashwagandha significantly reduced stress, anxiety, fatigue, and serum cortisol levels compared to placebo across multiple studies. The doses that produced these results ranged from 225 mg to 1,250 mg per day of root extract, with effects appearing at even the lower end of that range.
In one trial, 130 adults with self-reported stress took 300 mg of ashwagandha root extract daily for 90 days. By the end, participants had lower serum cortisol levels alongside improvements in perceived stress. Another study found that just 225 mg per day for 30 days was enough to lower saliva cortisol levels compared to placebo. These are relatively small doses, which matters because it suggests you don’t need to take large amounts to see a benefit.
Most people notice reductions in stress and anxiety within a few days to two weeks, though cortisol levels measured in blood tests typically take four to eight weeks of consistent use to show meaningful changes. Ashwagandha is classified as an adaptogen, meaning it helps your body calibrate its stress response rather than simply suppressing cortisol production. This makes it particularly well suited for people dealing with ongoing, everyday stress rather than acute spikes.
Phosphatidylserine: Best for Exercise-Related Spikes
If your cortisol spikes are tied to intense physical activity, phosphatidylserine (often labeled PS) has some of the most impressive numbers in the research. In a controlled trial, 600 mg per day for 10 days reduced peak cortisol concentrations by 39% and total cortisol exposure (measured as the area under the curve on a blood test) by 35% compared to placebo during moderate-intensity exercise.
Those are large effect sizes for a supplement. Phosphatidylserine is a fat-like molecule that’s naturally found in cell membranes, especially in the brain. It appears to blunt the cortisol response to physical stress specifically, which makes it a practical option for athletes or people whose training is intense enough to leave them feeling wired, unable to sleep, or slow to recover. For general life stress, the evidence is less robust than ashwagandha’s, so think of PS as a more targeted tool.
Omega-3 Fatty Acids
Fish oil isn’t typically marketed as a cortisol supplement, but there’s growing evidence it plays a role. In a 12-week trial, participants taking 2,400 mg of total omega-3s daily (1,000 mg EPA and 750 mg DHA) showed a significant decrease in morning cortisol levels by the end of the study compared to baseline. Morning cortisol is a particularly useful marker because it reflects your body’s baseline stress tone rather than a reaction to a specific event.
Omega-3s work differently from adaptogens. Rather than directly interfering with the stress hormone pathway, they reduce systemic inflammation, which is one of the signals that keeps cortisol production elevated. If you’re already taking fish oil for heart or brain health, the cortisol benefit is an added bonus. If you’re choosing a single supplement purely for cortisol, ashwagandha has stronger direct evidence, but omega-3s are a solid supporting player, especially for people whose stress is compounded by inflammation from poor diet or chronic conditions.
Vitamin C and Adrenal Health
Your adrenal glands contain some of the highest concentrations of vitamin C in the body, and they use it as a building block for cortisol production. That might sound counterintuitive, since taking more of a cortisol ingredient seems like it would raise levels, not lower them. But research suggests vitamin C actually helps keep cortisol within a normal range by acting as a brake on the stress response pathway. It modulates the hypothalamic-pituitary-adrenal axis directly, helping the feedback loop function properly so cortisol doesn’t stay elevated after the stressor has passed.
Most of the evidence for vitamin C’s cortisol effects comes from animal studies and mechanistic research rather than large human trials, so it sits a tier below ashwagandha in terms of proof. Still, because vitamin C is inexpensive, widely available, and has virtually no downside at reasonable doses, it’s a practical addition if you’re already taking something else for cortisol and want extra support for adrenal function.
L-Theanine for Acute Stress
L-theanine is an amino acid found naturally in tea leaves. It promotes calm without sedation by increasing calming brain wave activity, and at least one study found that saliva cortisol levels were lower two hours after L-theanine intake compared to caffeine intake. The effect is relatively fast-acting, which makes L-theanine useful for situational stress: a difficult meeting, a high-pressure exam, or a day when anxiety is running higher than usual.
L-theanine is not as well studied for long-term cortisol reduction as ashwagandha. Think of it as a complementary tool for acute moments rather than a standalone strategy for chronically high cortisol.
What About Rhodiola?
Rhodiola rosea is frequently listed alongside ashwagandha as an adaptogen for stress, and it does have evidence for improving mental performance and reducing fatigue. However, a controlled trial using 600 mg per day for four weeks in healthy men found that improvements in mental performance were not related to changes in cortisol release. Rhodiola may help you feel less stressed and more mentally sharp, but the mechanism doesn’t appear to run through cortisol the way ashwagandha’s does. If your primary goal is specifically lowering cortisol on a blood test, rhodiola is not the strongest pick.
Choosing the Right Approach
For most people dealing with chronic stress and wanting a single supplement to lower cortisol, ashwagandha at 300 to 600 mg per day of a standardized root extract is the best-supported starting point. Give it at least four to eight weeks before evaluating whether it’s working.
If your cortisol spikes are tied to heavy exercise, phosphatidylserine at 600 mg per day targets that specific problem more effectively. For a broader anti-inflammatory approach that supports cortisol regulation alongside cardiovascular and brain health, omega-3s in the range of 2,000 to 2,400 mg per day are a reasonable choice. And if you want fast-acting support for stressful moments, L-theanine (typically 100 to 200 mg) works within a couple of hours.
These supplements are not mutually exclusive. Ashwagandha plus omega-3s, for example, address cortisol through completely different mechanisms and can be taken together. The key variable that no supplement can replace is the lifestyle foundation: consistent sleep, regular moderate exercise, and stress management practices like breathing exercises or meditation all lower cortisol through the same pathways these supplements target, and often more powerfully.