April 3, 2005 YOUR DIET AND THE BRAINS IN YOUR BELLY AND YOUR HEAD The race is on to find a pill that will help us fight weight gain, especially around our bellies because millions of us are overweight and in danger of developing heart disease, diabetes, social ostracism and many other ills connected with obesity. Our being too fat, reportedly, leads to a $100 billion dollar in medical costs for the nation. The pharmaceutical companies are searching for a compound that can turn off the hunger centers in our brains or turn on the satiety centers. But which brain? Recent research has shown that we may have two brains--one in our heads and another in our stomachs. Do you eat when you are nervous or do you find it impossible to swallow a bite? While scientists are just now identifying the neurochemical connections between gut and brain, we all experience this interaction "in the pit of our stomachs" under periods of high emotion. In such instances, we are conscious of what is happening between our bellies and brains. Most of the time, however, we are unaware of this interaction. We may be in a "bad mood" and not realize it is because we skipped breakfast. Our nerves may be "on edge" because we had that third cup of coffee or we may feel sleepy after a "heavy meal" and still not make the connection between our central nervous systems and substances we ingested. Our mental function is directly related to what we eat or don't eat because our brains are chemical factories that produce dozens of different psychoactive drugs. We eat the starter materials for these brain chemicals which we make into the chemicals that affect our intelligence, memory, mood, appetite, and weight control. Our digestive systems also are chemical factories. In the linings of the esophagus, stomach, small intestine and colon, there are millions of nerve cells that send out stop-and-go messages to our brains. The components of this digestive control center are lumped under the title the enteric (from the Greek entera meaning bowels) nervous system. Current thinking among a number of scientists is that there is a "brain" in the gut, independent from the brain encased in the skull and that the enteric nervous system may be able to learn and remember independently of the central nervous system. Developmental biologists point out there is a clump of tissue, the neural crest-that forms early in the embryo. One section turns into the central nervous system. Another piece migrates to become the enteric nervous system. Later, the two nervous systems are connected via a telephonelike wire, the vagus nerve. Until relatively recently, people thought that the gut's muscles and sensory nerves were wired directly to the brain and that the brain controlled the gut through the vagus nerve that connects our stomachs and our brains. When scientists began to count nerve fibers in the gut, they found it contained more than 100 million-more than those of the spinal cord-yet the vagus nerve is "wired" to carry only a couple of thousand nerve fibers. The interaction between belly and brain via the vagus nerve is still somewhat mysterious. An increasing number of researchers believe there is a second brain in our bellies. Dr. Michael Gershon, professor of anatomy and cell biology at Columbia Presbyterian Medical Center, New York City, says the gut can work independently of the brain and spinal cord: "In an experiment in 1917, Swiss researchers excised a gut from a pig and blew into it. The isolated gut blew back. We now know that we can take gut tissue and put it in a nutrient solution and it will live for weeks. It has sensors so that if you touch it, it wiggles. This is due to a type of cell that responds to pressure and stimulation. These cells are found only in the gut and nowhere else in the body. That means the gut can function when cut off completely from the brain and spinal cord. Other organs of the body-for example, the bladder, the kidneys, the heart-cannot." Dr. Gershon says, "It is very simple. The gut does hard work. It takes in food, breaks it down, and digests it. This requires very complicated organic chemistry. For instance, the gut must produce the right amount of enzymes, send instructions to the pancreas to spurt more insulin for processing sugar or the gall bladder to secrete bile, and so forth. While all this is happening, the gut must protect its lining to keep all the nasty stuff from getting into the body because nothing we eat is sterile." The gut is "hard wired" and sends nerves directly to the gall bladder, for example, or the pancreas. It only takes about three percent of its instructions from the brain, according to Dr. Gershon. "If it had to have nerve connections to the brain for all the jobs it does, then the brain would have to be enormous and the trunk line between the gut and brain would take up the whole body." The brain in your head is very dependent upon the abilities of the brain in your belly. For you to survive, your belly must feed your brain by providing nutrients that will enable it to carry out its duties. One of the major functions of your central nervous system is communication - communication within its various parts - with the rest of your body, and with the outside world. Your brain has its own private "postal system." Each of your individual nerve cells, or neurons, can communicate with thousands of other cells by chemical messengers called neurotransmitters. Your body creates these brainy postal "employees" from substances in our diets. There are two ways neurotransmitters deliver their information between nerve cells: 1. Electrodynamically by "wire" in the brain and elsewhere in the body. Within nerve cells, signals are sent predominantly by wire (electrodynamically); conversely, the signals that are transmitted from one nerve cell to another "shoot the rapids" to carry a message across the gap between them-a process called synapsis. Since nerve cells do not touch one another, nature provided this chemical "message-carrying" system as well as the electronic "Internet" setup. The brain's communication service has an amazing capacity to deliver. It was not long ago that it was believed messages could be sent only between adjoining nerves. Now it is known that nerves can issue substances that travel throughout the body, affecting other nerves at distant sites. It has also been recently discovered that a single nerve is capable of sending out several messages, not just one, as previously believed. Understanding and separating the two "brains" is not easy. Imagine holding a lemon in your hand, cutting it open, and then sucking it. This is just a small example of how the sight, smell, taste and texture of foods can cause your brain to release digestive chemicals and elicit hormonal, heart, and kidney responses. This phenomenon is believed to be nature's way of priming your body to better absorb and use the nutrients you eat. The discovery that neurotransmitters - chemical agents that send messages between our brain cells are derived from the foods we eat - was a scientific leap forward. Now investigators gain a better understanding of those messages to control: In the near future, we then may be able to pop a pill that will help us control our weight. Will such pills that intercept the messages between the brain in our belly and the brain in our head have significant side-effects as diet pills have had in the past? Stay tuned.
Are there "butterflies" in your stomach when you have to give a speech, take an exam, or go through a rite of passage?
How is your control of your bladder and bowels when you are terribly frightened?
Why did this talent of the gut evolve?
2. Chemically, like a bottle tossed in the ocean.
Did you begin to salivate?
When you actually do sit down to a meal, your brain receives feedback from various organs as it is fueled up. What you choose to ingest, therefore, has a profound influence on your central nervous system and thus on your ability to think, your mood, your energy and, in fact your survival.
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