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Myostatin-Blocker Bust

Can the muscle-growth-inhibiting protein be stopped?

About two years ago dramatic advertisements began appearing in bodybuilding magazines proclaiming that you could now ‘exceed your genetic potential.’ The ads usually showed freaky animals, such as bulls whose bodies rippled with muscle or rats that appeared twice as hefty as their littermates. Those animals were either born without genes that code for myostatin or had been genetically engineered to block the activity of myostatin. The featured product was a natural myostatin blocker.

Discovered in 1997, myostatin is a natural protein in the body that inhibits muscular growth. It also promotes fat accretion by lowering levels of leptin, another protein involved in fat synthesis. Scientists believe that myostatin inhibits the function of special muscle satellite cells that are required for muscle repair and growth. When myostatin is blocked or absent, muscles seem to grow at an unprecedented rate.

It didn’t take long for someone in the supplement industry to figure out the benefits of producing a myostatin blocker. A candidate soon emerged in the form of Cystoseira canariensis, a brown sea algae. A study published in an obscure Bulgarian physiology journal found that the seaweed appeared to bind to and block the activity of myostatin. The problem was that this occurred in vitro’in a test-tube environment. No human trials had been done to see how the seaweed would affect myostatin in the human body.

Such minor details didn’t deter some companies, which rushed the seaweed supplement on to the market, touting it as the solution for those who experienced slow muscle gains or who wanted to exceed their genetic potential. The ads implied that using the supplement would produce results similar to those seen in the myostatin-deficient animals: massive muscularity with little or no apparent bodyfat’the bodybuilding Holy Grail.

Soon after the original myostatin supplement was released for sale, I contacted the scientist from Johns Hopkins University who had discovered myostatin to ask about the potential usefulness of the new supplement. He expressed skepticism, noting that myostatin research was still in its infancy and the full implications of blocking the protein in humans weren’t yet known. Even if the supplement worked as advertised, he suggested, it would be premature to offer it for sale.

Somewhere along the line the initial excitement about myostatin-blocking supplements petered out. Could it be that the products didn’t work after all? A new study answers that question and explains why the supplements likely lost popularity.1

Twenty-two untrained men were randomly assigned to either a placebo or myostatin-blocker group. They trained three days a week for 12 weeks and took 1,200 milligrams’the recommended dose’daily of a commercial myostatin-blocking supplement. There were no differences in strength, muscle gains or fat loss between those who took the supplement and those in the placebo group. Why did the myostatin blocker fail to work?

It turns out that another natural substance in the body, follistatin-related gene protein (FLRG), inhibits myostatin. The myostatin-blocking supplement interfered with the activity of that protein, which prevented any inhibition of myostatin in the body. In other words, the supplement worked against itself, nullifying its own activity.

The authors noted a few potential weaknesses of their study. One was the use of untrained subjects, who may not react to the supplement in the same way as more experienced trainees do. Another problem was the dose, which may have been insufficient to effectively block myostatin. On the other hand, considering why the myostatin blocker failed to work, it’s safe to say that this type of supplement works better in a test tube than it does in the human body, where more complex mechanisms govern its behavior.

The lesson here: Never trust claims made about supplements that haven’t been tested on humans and expect the products to provide some measure of effectiveness. Or, to put it another way, don’t piss on my leg and tell me it’s raining. IM

1 Willoughby, D. (2004). Effects of an alleged myostatin-binding supplement and heavy resistance training on serum myostatin, muscle strength and mass, and body composition. Int J Sport Nutr Exerc Metabol. 14:461-72.

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