Serotonin and Your Body

Editor's Note: This article was originally written by patient expert Judith Wurtman.

I was losing the argument.   According to my neighbor, it was possible to take serotonin as a supplement and not only lose weight but also vanquish the symptoms of stress, PMS and menopause. "Just go to the website and you will see all the testimonials from people who have been helped by the serotonin supplement," she told me, referring to a serotonin supplement-based weight-loss program.   Pointing out to her that taking serotonin as a pill was useless because serotonin in the body never gets into the brain made no impact.   "Well maybe the scientists are wrong," she asserted. "Anyway, this serotonin supplement works"

It occurred to me that if what she said were really true, then the millions of people who are taking antidepressants to increase serotonin activity could throw away their pills. Women would never suffer from PMS and menopause would hardly be noticed.   However, a fact is a fact and the fact is that there is a barrier between the brain and the bloodstream. And this so-called wall around the brain prevents serotonin in the blood stream from ever entering the brain.

"Did you know that there is serotonin in your bloodstream and it comes from your small intestine?" I told her." In fact, 95% of all the serotonin in your body is made there. Only 5% is made in your brain.   Of course, none of the serotonin made in your gut gets into the brain either."

When she asked what was the point of having the gut churn out all that serotonin if it wasn't going to help either her mood or PMS, I told her that recently, scientists had discovered that this serotonin was involved in bone health. "I thought my bones depended on calcium, vitamin D, exercise, hormones, all that stuff, " she replied. "Well according to research by a group from Columbia University, people with too much serotonin in their gut may have weak bones," I said.

Having captured her attention, I went on to tell her about Dr Gerard Karsenty and his team from the Department of Genetics and Development at Columbia University 's College of Physicians and Surgeons. As reported last November, they discovered a gene mutation that may explain why some people form abnormal bones.   Infants can be born with bones that are too dense or too fragile. Either situation is bad. The gene is called Lrp5 and it makes a protein called Lrp5.   Mutations in the gene can cause the Lrp5 protein to be too active or not active enough. If the protein is not active enough, the bones are so fragile that simply standing up and putting weight on the bones is enough to break them.     If the protein is too active, then abnormally dense bones are formed.

"So my mother, who has just told she has osteoporosis, has this gene?" she asked. "No," I replied. "According to the article, the osteoporosis they are talking about is something that is present at birth."   At this point my neighbor murmured something about having a lot of errands to do and started to leave, so I got to the point.

"Here is where serotonin comes in.   The gene also controls serotonin production in the gut. Humans who have genetic osteoporosis or fragile, weak bones had much more serotonin in their gut than people with normal bones. And patients with abnormally dense bones had 50% less serotonin than those with healthy bones.

"However the researchers had to see whether it was simply a coincidence that serotonin levels seemed to be connected to bone formation. They tested the link between the gene, serotonin and bone formation by tinkering with the serotonin levels of mice. Mice who were born with one form of the mutation make too much serotonin in their gut and develop breakable bones. The serotonin is made from tryptophan, which the mice get from the protein they eat. So the researchers gave the mice a diet very low in tryptophan and the serotonin levels dropped to normal. As a result, the mice had healthy bones."

Now my neighbor looked worried. "Do you mean to say that if I keep taking the serotonin supplement, I might have problems with my bones?" " No one knows," I answered. "After all, until very recently, there was no such thing as a serotonin supplement. And maybe the amount of serotonin in the supplement is less than what your gut is making anyway. But since you are interested in serotonin in your brain, why don't you get your brain to make it the way nature intended? Eat carbohydrates. That way, your brain, not your intestinal tract, will be making more serotonin, which is what you want. When you eat carbs, your brain is able to capture some of the tryptophan in your bloodstream and make the serotonin it needs. And whatever is happening in your gut won't be affected at all.

"And fortunately, there is a normal and natural way of getting serotonin to increase in your brain without risking the health of your bones. Eat carbohydrate. As long as you eat something starchy or sweet on an empty stomach, there will be plenty of serotonin in your brain."

"But won't my gut make more serotonin if I eat carbohydrates?"

"No, it only works for the brain."

As we finally parted from each other, I heard her muttering, " I think I'll go the bakery and get some fresh bread,"