Serotonin is nature’s own appetite suppressant. This powerful brain chemical curbs cravings and shuts off appetite. It makes you feel satisfied even if your stomach is not full. The result is eating less and losing weight.
A natural mood regulator, serotonin makes you feel emotionally stable, less anxious, more tranquil, and even more focused and energetic.
Serotonin can be made only after sweet or starchy carbohydrates are eaten.
More than thirty years ago, extensive studies at MIT carried out by Richard Wurtman, M.D., showed that tryptophan, the building block of serotonin, could get into the brain only after sweet or starchy carbohydrates were eaten. Although tryptophan is an amino acid and found in all protein, eating protein prevents tryptophan from passing through a barrier from the blood into the brain. The reason is simply numbers: tryptophan competes for an entry point into the brain with some other amino acids. There are more of those other amino acids in the blood than tryptophan after protein is eaten. So in the competition to get into the brain, tryptophan is at a total disadvantage and very little gets in after a protein meal like turkey or snack like yogurt.
But carbohydrates tip the odds in tryptophan’s favor. All carbohydrates (except fruit) are digested to glucose in the intestinal tract. When glucose enters the bloodstream, insulin is released and pushes nutrients such as amino acids into the cells of the heart, liver and other organs. As it does this, tryptophan stays behind in the bloodstream. Now there is more tryptophan in the blood than the competing amino acids. As the blood passes by the barrier into the brain, tryptophan can get in. The tryptophan is immediately converted to serotonin, and the soothing and appetite controlling effects of this brain chemical are soon felt.
Our studies with volunteers found that when people consumed a pre-meal carbohydrate drink that made more serotonin, they became less hungry and were able to control their calorie intake. Volunteers whose drinks contained protein—so that serotonin was not made—did not experience any decrease in their appetite.
Most of us have experienced the carbohydrate-serotonin effect on our appetite even though we were not aware of the connection. Have you ever munched on rolls or bread while waiting for the main course to be served in a restaurant? By the time dinner is served, twenty minutes or so after you ate the roll, your appetite has been downsized. “I don’t even feel that hungry,” is a common response when the plate is put down on the table.
This blunting of appetite is not because you may have eaten 120 calories of roll. It is caused by new serotonin putting a brake on your appetite.
Successful weight loss depends on the power of serotonin to control food intake.
The carbohydrate-serotonin connection has a direct impact on our emotional state, too. Drugs that increase serotonin activity have been used for several decades as a therapy for mood disorders. However, our studies showed that natural changes in serotonin could have a profound impact on daily fluctuations in mood, energy levels, and attention. In one of our early studies, we found that our volunteers became slightly depressed, anxious, tired, and irritable around 3 to 5 p.m. every day. At the same time, they experienced, in the words of one volunteer “a jaw-aching need to eat something sweet or starchy.” Several studies later, we were able to state that late afternoon seems to be a universal carbohydrate-craving time, and people who experience this craving use carbohydrates to “self-medicate” themselves. Carbohydrate cravers who consume a sweet or starchy snack are increasing serotonin naturally.
We carried out careful clinical studies to measure the effect of carbohydrates on mood and to make sure that the effect was not just due to taste or the effect of taking a break from work. Volunteers, all carbohydrate cravers, were given a carbohydrate or protein- containing food or drink that had identical tastes. Their moods, concentration and energy were measured before and after they consumed the test beverages. The carbohydrate serotonin-producing beverage improved their moods but the protein-containing beverage had no effect on either their mood or their appetite.
