The Hormones of Digestion

After writing an article on the molecular link between obesity and high fructose corn syrup it became apparent how important hormones are in human digestion. How else would your stomach know when to churn, or your pancreas to release digestive juices? And what happens to this delicate system when we start eating refined foods which have been crafted so recently in human history?

According to the National Digestive Diseases Clearing House three hormones (Gastrin, Secretin, and CCK) are primarily responsible for digestion:

Gastrin causes the stomach to produce an acid for dissolving and digesting some foods. Gastrin is also necessary for normal cell growth in the lining of the stomach, small intestine, and colon. Secretin causes the pancreas to send out a digestive juice that is rich in bicarbonate. The bicarbonate helps neutralize the acidic stomach contents as they enter the small intestine. Secretin also stimulates the stomach to produce pepsin, an enzyme that digests protein, and stimulates the liver to produce bile. CCK causes the pancreas to produce the enzymes of pancreatic juice, and causes the gallbladder to empty. It also promotes normal cell growth of the pancreas.

In terms of regulating appitite the NIDDK suggests that Ghrelin and Peptide YY play important roles:

Ghrelin is produced in the stomach and upper intestine in the absence of food in the digestive system and stimulates appetite. Peptide YY is produced in the digestive tract in response to a meal in the system and inhibits appetite.
NIDDK fails to mention anything about leptin, another hormone to tell the body it is full, and the one that is theoretically suppressed by high fructose corn syrup.

According to the Wikipedia article on appetite, there is much to learn in how exactly the body tells us when to be hungry and when to be full. Wikipedia puts the current understanding of research as follows:

The hypothalamus senses external stimuli mainly through a number of hormones such as leptin, ghrelin, PYY 3-36, orexin and cholecystokinin; all modify the hypothalamic response. They are produced by the digestive tract and by adipose tissue (leptin). Systemic mediators, such as tumor necrosis factor-alpha (TNF?), interleukins 1 and 6 and corticotropin-releasing hormone (CRH) influence appetite negatively; this mechanism explains why ill people often eat less.

It will be interesting to see what research will tell us as our understanding of hormone regulation advances. As for now, those looking to "feel full" faster, and lose weight, would do well to eat foods low in refined sugars and fats, and to stay away from addictive snacking foods like peanuts. Instead try focus on high fiber, high water, containing foods that can help fill the stomach with low calories. Another tip would be to eat slowly and to wait twenty minutes to let the body signal to you that you are full. As a rule if you are still hungry after 20 minutes, then you can eat something else.

Yet another trick is to serve plates in the kitchen and leave the pots there. When the food is out of sight you are less tempted to take seconds, more happy to enjoy the food slowly, and share in good conversation. You wouldn't want to let your hormones get the best of you.