Serotonin and Your Bones

Go to Health: Serotonin and your bones

Neurotransmitters are chemicals in our bodies which relay and regulate signals between a neuron (nerve cell) and another cell. The neurotransmitter serotonin is best known for its role in the brain, where it helps regulate mood, sexual desire & function, appetite, sleep, memory & learning, temperature regulation, and some social behaviors such as assertiveness and aggression. However, 90% of our body's total serotonin is made by the cells of the gut, where it is used to regulate intestinal movement. It is synthesized from tryptophan, an amino acid found in protein foods, including plant foods. When you have a ‘gut feeling’, it’s real - you are reacting to serotonin and other neurotransmitters in the intestinal tract! Blood platelets pick up serotonin from the gut and transport it to blood vessels, the heart, the liver and other organs, including bone cells. (Platelets are tiny cells, without a nucleus, that come from white blood cells in the bone marrow. One of their main functions is to prevent bleeding.)

Bones may seem dense, but inside they have honeycomb-like scaffolding that allow them to be strong without being too heavy. Throughout life they are constantly remodeling themselves, making new tissue where needed and clearing out old bone. In recent years, studies have shown that there are molecules that transport serotonin into bone cells. This was an unexpected finding, and research into its meaning is ongoing. What has emerged is that bones get weaker in the presence of more serotonin, and stronger with less.

SSRIs This finding is important for the 8-10% of adults who are taking SSRIs (selective serotonin reuptake inhibitors) to treat depression. These drugs increase the amount of serotonin in the body – thereby helping mood but potentially weakening bone. Studies in Canada and the US have shown greater rates of bone loss and fractures among people taking SSRIs. While these antidepressant drugs – such as Prozac, Paxil, Zoloft, Celexa, Luvox, Lexapro and others – have been very important for many depressed people, their possible side effects on bone should be more widely known.

Users of SSRIs and most midlife women should consider having a test for bone density (called a DEXA scan), and should also work on measures to help build strong bones. New bone growth is helped by exercise, especially strength training. Walk, jog, hike, play tennis or soccer – depending on your age and abilities. A good book for strength training is Growing Stronger – Strength Training for Older Adults. You can download it for free at
http://growingstronger.nutrition.tufts.edu/book.html.

*Most people need extra Vitamin D - get a blood level of 25 hydroxy vitamin D. A level above 30 ng/ml is desirable, and 50 ng/ml is considered optimum. You will probably need to take at least 1000 IU of supplemental D daily.
*Get 1000 mg of calcium and at least 500 mg of magnesium daily in food and supplements. Eat a healthy diet with lots of fruits and vegetables (red, orange and yellow pigments in plant food inhibit bone breakdown).
*Don’t smoke
* If you drink alcohol, stop at 1 drink daily for women and 2 for men.
*Taking sex hormones (estrogen, progesterone, testosterone) by pill or patch can help bone strength but also can increase cancer risk and is not advisable for most people over 50.
*Your doctor may advise a medication to increase bone strength; these can be helpful, but be aware of their side effects too..
Sadja Greenwood, MD, MPH –back issues on this blog. Leave a message!