THE INTESTINAL TRACT

The small intestine is made up of three distinct portions. In se­quence, they are the duodenum, the jejunum, and the ileum. The duodenum is the first segment to receive the food mass through the pylorus after its processing in the stomach. You should note that the

8 Optimal Nutrition for Optimal Health

additional digestive factors in the duodenum are alkaline in nature, and the acid-dependent stomach enzymes are typically shut down as soon as they are adequately mixed in with the alkaline duodenal environment. Defects in maintaining this alkaline environment can lead to duodenal ulcers, the most common form of ulcer disease, since the duodenum is ill equipped to deal with unneutralized stomach acids.

The duodenum receives important digestive factors from the pancreas, the liver, and the gallbladder, all of which are activated in an alkaline environment. The pancreatic enzymes serve to break down the protein-derived peptides into amino acids, the carbohy­drates and starches into simpler sugar chains, and the lipids into fatty acids and glycerol. The bile from the liver and gallbladder coats the water-insoluble lipids, which enables the pancreatic en­zymes to attack them and break them down. This process is known as emulsification, which essentially serves a detergent function, al­lowing water-insoluble substances to be processed in a water-based environment.

The lining of the duodenum begins the primary absorption of the broken-down food components. However, the jejunum, the next portion of the small intestine, completes most of this absorptive process. The lining of the jejunum, which is composed of numerous microscopic fingerlike projections containing even more enzymes, also serves to help complete the final breakdown of carbohydrates and peptides to single sugar molecules and amino acids before ab­sorbing them into the bloodstream. Vitamin absorption also takes place here. The fatty lipids in the diet are critical in promoting the absorption of the fat-soluble vitamins (A, D, E, and K).

The final portion of the small intestine, the ileum, completes most of the nutrient absorption that is to take place. Much of the bile gets reabsorbed here, effectively recycling it for later use.

From the ileum, the food mass passes into the colon, or large in­testine. The colon absorbs few nutrients, but it reabsorbs most of the

The Importance of Proper Digestion 9

water and electrolytes in the processed food mass, which is then de­livered to the rectum for subsequent elimination.