Because U.S. government surveys have found that one-third to one-half of all adults take vitamin and mineral supplements daily, government regulators are taking a closer look at nutritional supplements of all types. This is especially true of those taken in large amounts by bodybuilders and other athletes who hope that supplementation will make a difference in their performance.

One of the supplement substances being closely examined is nitric oxide (NO), which is the primary component of NO-Xplode, manufactured by BSN. To understand what’s being looked at here, you need to know that NO is the amino acid arginine and arginine alpha-ketoglutarate (AKG) repackaged with a new name. NO is a free-form gas that’s produced in the body and used for intercellular communication, or communication between the body’s cells.

Enzymes in the body break down the amino acid arginine to make this gas. A molecule consisting of one atom of nitrogen and one atom of oxygen, NO is produced when the amino acid L-arginine is converted into L-citrulline through an enzyme group known as nitric oxide synthase (NOS).

NObel Prize

Discovering how NO works in our bodies is an exciting, important chapter in the history of cardiovascular medicine. In 1998, the Nobel Prize was awarded to three Americans for their independent discoveries concerning NO as a signaling molecule in the cardiovascular system, one that produces another substance known as a second messenger. Second messengers help in some way to carry a message from the outside of the cell to the inside.

Faulty Extrapolation?

Supplement manufacturers and many bodybuilders have taken that fact to a theoretical level unsupported by medical research. The theory is that supplementation creates and sustains levels of NO in the skeletal muscles—levels that are assumed to enhance oxygen delivery, glucose uptake, muscle velocity, and muscle growth.

However, when researchers at Baylor University in Texas examined the effects of AKG supplementation on body composition and training adaptations in experienced gym users, they found no significant differences between the body mass, fat-free mass, fat mass, or percentage of body fat measurements of those taking the supplement over those in the control group. Researchers concluded that while supplementation may enable users to increase bench presses by one repetition, no evidence exists to show that NO affects body composition.

NO Evidence?

Another study also found that supplementing with NO does not contribute to changes in body mass, fat-free mass, fat mass, or percentage of body fat. “The primary ingredient in NO is arginine, which has been shown to have no beneficial muscle building effects,” one researcher stated.

Judging from these findings, NO supplements are not helpful. However, they remain popular with bodybuilders, who are particularly interested in the fact that NO enhances blood flow, thereby delivering additional nutrients to muscles.

While NO is itself beneficial, it’s important to note that no solid medical evidence exists that supports the idea that taking it in supplement form does anything particularly beneficial for your body. Our bodies appear to manufacture sufficient NO to take care of our health needs. Indeed, in supplement form, NO can cause diarrhea and nausea.

—Julie Crawshaw