The Serotonin-Bone Connection

Our understanding of healthy bones got a little more complicated late last year, the consequence of an eye-opening study on serotonin and bone health.

Serotonin is a neurotransmitter that influences mood. General medical opinion is that low serotonin causes depression, anxiety, and aggressive behavior. But 95 percent of the body’s serotonin is produced in the gut, not in the brain. And serotonin made in the gut cannot be transported to the brain. So what does all this serotonin do?

A recent study, by Gerard Karsenty, PhD, of the Columbia University College of Physicians and Surgeons, New York City, determined that gut serotonin governs bone formation. He and his colleagues reported in the journal Cell that high levels of serotonin decreased bone density. Conversely, low levels of serotonin increased bone density.

The implications of this research are profound. Anti-depressants are the most prescribed class of drugs in the United States. In 2005, doctors wrote 118 million prescriptions for anti-depressants, and most of these drugs (e.g., Prozac and Zoloft) work, according to the drug companies, by increasing levels of serotonin. Do they affect gut serotonin levels?

It’s likely that they do because many of the side effects of these drugs affect the gastrointestinal tract. When considered in light of Karsenty's study, these drugs may also be setting the stage for an epidemic of osteoporosis.

There are so many healthy nondrug ways to fight depression. Many are nutritional and work through a panoply of biochemical pathways. Others are lifestyle oriented and include yoga and exercise. And the same is true when it comes to maintaining healthy bones. There are few things that a drug can do that a nutrient cannot do better and with greater safety.