What Is Myostatin? The Body's Muscle Brake, Explained

Your body has an accelerator for building muscle, and it also has a brake. The brake is a protein called myostatin. It has fascinated scientists for almost 30 years because of what happens when it is missing. Here is what myostatin is, what affects it and what a 2023 PeptiStrong trial found.

What myostatin is

Myostatin, also called GDF-8, is a signaling protein made mainly by muscle cells. Its job is to limit muscle growth. It belongs to a large family of growth factors that help the body keep tissues at the right size, and in muscle it acts as a negative regulator: more myostatin activity means less growth.

That may sound counterproductive, but a brake is useful. Muscle is expensive tissue to build and maintain, and myostatin is one of the ways the body keeps it in balance with its energy supply.

What happens without it

Myostatin was discovered in 1997 by researchers at Johns Hopkins. When they switched off its gene in mice, individual muscles grew two to three times heavier than normal, from both larger and more numerous muscle fibers. The same year, scientists traced the dramatic "double-muscled" look of Belgian Blue cattle to natural mutations in the myostatin gene.

In 2004, physicians described a child in Germany with a myostatin mutation who was born with unusually large muscles, confirming that the brake works in people too.

What affects myostatin

• Strength training. In a 2003 study, nine weeks of heavy resistance training lowered myostatin gene expression in muscle by 37 percent in men and women. It is one of many signals through which training tells muscle to grow.
• Inactivity and illness. Disuse, aging and many chronic illnesses are associated with muscle loss, and myostatin is one of the pathways researchers study in those settings.
• Experimental drugs. Several drugs that target myostatin or related signals are in clinical development, including for protecting muscle during weight loss. None is approved for building muscle, and they are prescription drug candidates, not supplements.

What the PeptiStrong trial measured

PeptiStrong is a network of peptides made from fava bean protein. In a 2023 double-blind trial, 30 healthy men aged 30 to 45 took 2.4 g of PeptiStrong or a placebo daily for 14 days, then did a hard workout designed to cause muscle soreness. Researchers then tracked strength and blood markers for 72 hours.

The lower myostatin reading is an interesting biomarker finding that fits with the better strength recovery, but it is one marker in one small trial. It does not make PeptiStrong a "myostatin blocker," and you should be skeptical of any supplement sold that way. Our explainer, what is PeptiStrong, covers all of the published research.

Who should check with a physician first

Be wary of products sold online as myostatin inhibitors, especially injectables. Talk to your physician before using PeptiStrong if you have G6PD deficiency or a history of favism, a legume allergy, or if you are pregnant, breastfeeding, under 18 or take prescription medication.

How Vita Bloom fits

Our PeptiStrong Muscle Peptides deliver 2.4 g of PeptiStrong® in four capsules a day, the amount used in the 2023 trial, as the only active ingredient. Take them daily with water, alongside resistance training, and give it at least eight weeks. For recovery tips, read how to speed up muscle recovery.

Frequently asked questions

What does myostatin do?

It limits muscle growth. It acts as a brake that keeps muscle mass in balance.

How can I lower myostatin naturally?

Heavy resistance training is the best-documented natural lever. In one study, nine weeks of strength training lowered myostatin gene expression in muscle by 37 percent.

Are myostatin inhibitors safe?

Drugs that target myostatin are still experimental and are not approved for building muscle. Products sold online as myostatin inhibitors are not a safe substitute.

Does PeptiStrong block myostatin?

We do not describe it that way. In one 2023 trial, blood myostatin was lower in the PeptiStrong group after a hard workout, alongside better strength recovery and less fatigue.

PeptiStrong® is a registered trademark of Nuritas Ltd. Vita Bloom Labs uses the branded ingredient and is not otherwise affiliated with Nuritas.

These statements have not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure, or prevent any disease.