Cortisol Blockers and Supplements for Weight Training

Athlete exercising with dumbbells

Westend61 / Getty Images

Cortisol blockers are drugs and supplements that are designed to lower your cortisol level. They have medical use in treating hormonal disorders such as Cushing’s syndrome.

Cortisol blocker supplements are also marketed as a training aid, weight loss, and stress relief remedy. This has resulted in Federal Trade Commission (FTC) and Department of Agriculture (USDA) charges of unsubstantiated medical claims and false advertising.

Weight trainers might use cortisol blockers believing they prevent cortisol from degrading their muscle. The stress of hard workouts might raise cortisol levels, and a blocker might help prevent cortisol-related immune system slowdown that can lead to infection.

What Cortisol Does

Cortisol is a human steroid hormone produced by the adrenal glands. It has many important functions. Here's an overview of some of things it does.

  • Acts as a "breaking-down" hormone (catabolic), rather than a "building-up" hormone (anabolic)
  • Provides glucose to the body when it needs it
  • Provides natural pain relief
  • Regulates the immune system
  • Responds to stressful situations, mental or physical

From a weight training and bodybuilding perspective, breaking down body tissue is not what we want to happen, because that means muscle and bone get broken down and fat builds up. Cortisol does this mainly to supply the body with important glucose at times of physical or mental stress. It’s easy to see why people who sell supplements have come up with something called “cortisol blockers.”

What Are Cortisol Blockers?

Although many trade-named products are available, one prominent cortisol-blocking agent is called phosphatidylserine.

Although phosphatidylserine was investigated in 2006 for its potential to block cortisol and therefore improve training or performance, no clear effect has been established.

The lack of a clear link is not surprising considering the complexities of steroid hormones. One possible effect of long-term supplement use is that your body could change the way it naturally produces cortisol.

When you stop taking the supplement, you get an unnatural production of cortisol leading to illness. These are not hormones to be played around with.

Unsubstantiated Claims

The USDA sent a warning letter to the president of warning of unsubstantiated medical claims for their Higher Power CortiShed, EAS C3, Now Relora, and WRH CortiSlim products.

The claims included controlling fat production, achieving maximum leanness, and maintaining muscle mass. For CortiSlim, the USDA took issue with claims that it balanced blood-sugar, reduced cravings, helped appetite control, boosted fat-burning, and optimized metabolic rate.

The FTC filed suit against the makers of CortiSlim and CortiStress in 2005 for deceptively marketing them for weight loss and stress relief.

How to Manage Cortisol Naturally

The best thing you can do to manage extremes of cortisol production during your workout are:

  • Get plenty of sleep and try not to get too stressed in daily life.
  • Avoid training on an empty stomach because a little food in the stomach, especially carbohydrate food, will keep cortisol from rising too much by providing a normal level of glucose in the bloodstream.
  • Take some food or drink during the workout to keep glucose circulating in the bloodstream for long and hard workouts.

If you do those things, cortisol should never be a problem. Cortisol is not your enemy. It has an important role to play in daily life and trying to manipulate it for training purposes is bound to fail.

2 Sources
Verywell Fit uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. Kingsley M. Effects of Phosphatidylserine Supplementation on Exercising HumansSports Med. 2006;36(8):657‐669. doi:10.2165/00007256-200636080-00003

  2. U.S. Federal Trade Commission. FTC Targets Products Claiming to Affect the Stress Hormone Cortisol. 2005.

By Paul Rogers
Paul Rogers is a personal trainer with experience in a wide range of sports, including track, triathlon, marathon, hockey, tennis, and baseball.