A New Cortisol-Reducing Supplement Claims to Help You Train Harder and Recover Faster. But Does It Work—And Do You Even Need It?

5 min readCortisol has had some seriously negative PR over the past few years, especially when it comes to workouts. The stress hormone is often framed as the hidden force behind poor recovery, stalled progress, and lingering fatigue. Now, a new “cortisol-reducing” supplement from the brand KA-EX promises to lower stress, prevent burnout, and help you train harder. But does it work—and do you even need one in the first place?As a reminder, cortisol increases any time the body faces mental or physical challenges like a work deadline, illness, or intense workout, says Tania Elliott, MD, a dual board-certified internist and immunologist. However, cortisol isn’t inherently harmful—everyone has (and needs) it. When you have a healthy amount of it, cortisol provides energy for the body, keeps blood pressure stable, reduces inflammation, and supports mental alertness, she adds.Meet the experts: Tania Elliott, MD, is a dual board-certified internist and immunologist. Peter Ronai, EP-C, CSCS, is an exercise physiologist, certified strength and conditioning specialist, and clinical professor of exercise science in the College of Health Professions at Sacred Heart University. Mark Kovacs, PhD, CSCS, is an exercise physiologist, longevity and human performance specialist, and founder of the Kovacs Institute.But too much stress, like from overtraining, can cause your sleep, mood, anxiety, exercise recovery, and immune function to suffer, says Peter Ronai, EP-C, CSCS, an exercise physiologist and clinical professor of exercise science. Chronically elevated stress levels can also impair muscle protein synthesis, making it harder to build or maintain muscle mass, while increasing body fat.So, what role does exercise play in elevating cortisol? And can a cortisol-reducing supplement actually make a difference in your performance and recovery? Ahead, experts break down what to know.The Role of Cortisol in ExerciseWhen you work out, your cortisol rises temporarily, which helps to break down stored carbohydrates and fat to fuel your exercise. “You need cortisol to function, adapt, and perform,” says Mark Kovacs, PhD, CSCS, an exercise physiologist and human performance specialist.The intensity of the workout determines how much your cortisol increases. Very high-intensity exercise (like HIIT workouts or heavy weightlifting) causes dramatic spikes, according to a 2021 review of studies on the effects of exercise intensities and modalities on cortisol production in the Journal of Exercise and Nutrition. Moderate-intensity exercise (like jogging or using the elliptical) can also raise cortisol levels, though the increase is generally more modest than with high-intensity exercise; whereas low-intensity exercise (like walking or yoga) tends to have little to no effect, Ronai says. Over time, regular exercise-induced cortisol spikes can help your body build resilience to these hormone fluctuations.Cortisol levels typically return to baseline within two and a half hours after exercise, says Dr. Elliott. However, workout duration and total stress load also matter. A short, intense workout may create a sharp spike that drops quickly afterward, Kovacs adds. Meanwhile, a long endurance session can keep cortisol elevated for an extended period of time because the body is working for longer.“The problems only arise when cortisol remains chronically elevated, which can happen due to excessive high-volume training without adequate rest, ongoing stress, or a medical condition such as Cushing syndrome,” Dr. Elliott says. In those cases, high cortisol can start to work against the body, disrupting recovery and tissue repair, contributing to muscle loss, and increasing visceral fat (deep abdominal fat that wraps around the internal organs). These are the kind of cases where cortisol-reducing supplements intend to offer support, particularly for people engaging in intense, extensive training—but can they actually have an impact?How Cortisol-Reducing Supplements WorkThe idea behind this type of supplement is to help cortisol levels return to baseline after periods of intense training, therefore supporting recovery. In theory, they’ll improve your workout performance by allowing the body to recover more effectively, Ronai says.Common ingredients include phosphatidylserine, magnesium, L-theanine, tryptophan, and amino acids. Kovacs says these ingredients may help regulate the body’s stress response system, particularly the hypothalamic-pituitary-adrenal axis—they may also support nervous system relaxation, sleep quality, and/or neurotransmitter function. However, the research behind these supplements is mixed and depends heavily on the ingredient and dosage.There’s some evidence that phosphatidylserine can reduce your cortisol response to exercise, Kovacs says. Magnesium supports nervous system function, muscle relaxation, and sleep, while L-theanine has evidence for promoting relaxation and sleep quality, though it’s not a cortisol-lowering agent on its own, he adds. Tryptophan can aid sleep regulation since it’s a precursor to serotonin and melatonin, but the effect depends on the dose, timing, and individual.There’s also a lack of transparency regarding the research behind KA-EX’s new supplement, Ronai says. While the brand claims their supp can help cortisol levels return to baseline faster, improve REM sleep, and support better heart rate variability (HRV), it does not publicly disclose study links or key details about the research. For instance, we’re not sure who was tested or how because its clinical findings do not include information about study designs, sample size, participant population, control conditions, or funding sources (which could point to biases). It’s also not clear whether the outcomes translate to better performance or injury reduction.Shop Our Favorite Workout ClothesNew Balance Essential Run BraNow 30% OffCredit: Courtesylululemon Ebb to Street Tank TopCredit: CourtesyAlo Airlift High-Waist Suit Up LeggingCredit: CourtesyHowever, even if a product like KA-EX’s can lower cortisol, it doesn’t mean it’ll automatically improve your athletic performance. You may have better sleep and autonomic recovery (when the automatic nervous system returns to a state of balance after stress or physical exertion), and feel less tired, Kovacs says. “But that’s different from saying these supplements directly make someone stronger, faster, or fitter.” Your ability to perform better depends far more on your lifestyle habits. (More on that in a sec.)Whether You Should InvestExperts don’t recommend reaching for a supplement as your first line of defense. “If someone is under-sleeping, under-eating, overtraining, or highly stressed, a supplement will not fix the root problem,” Kovacs says. Foundational habits should come first: Focus on getting seven to nine hours of sleep a night, balanced nutrition, adequate hydration, and effective stress management.Grow strength and muscle with our exclusive body recomp planTraining habits also matter. “The body can adapt well to hard exercise when it’s supported by enough sleep, nutrition, and hydration, but the problem occurs when high-volume or high-intensity training continues without adequate recovery,” Kovacs says. Additionally, a pattern of declining performance despite training harder is a warning sign. In those cases, the solution is smarter workload load management: alternating hard and easy training days, scheduling recovery weeks, avoiding consecutive high-intensity sessions, and prioritizing rest.If you feel like you’re doing everything “right” lifestyle-wise but still struggle with stress or recovery challenges, Ronai recommends talking with your doctor. While some cortisol and stress are normal and necessary for your body to function well, your healthcare provider can help determine whether you might benefit from additional support.Find the Perfect Women’s Health Training Program for YouJustin SteeleRona Ahdout//Hearst OwnedAndi Breitowich is a freelance writer who covers health, fitness, relationships, beauty, and smart living. She is a graduate of Emory University and Northwestern University's Medill School of Journalism. Her work has appeared in Women's Health, POPSUGAR, Food & Wine, What To Expect, Cosmopolitan, Men's Health, and elsewhere. As a former collegiate pole vaulter, she loves all things fitness and has yet to meet a group workout class she doesn't like.