Food digestion, (especially protein), which begins in the stomach, continues in the small intestine. The food bolus (chyme) passes into the duodenum as a result of smooth muscle contraction (peristaltic movement). This causes a reflex that decreases production of stomach acid (HCL) and also slows further emptying of the stomach. The reflex is triggered by: presence of acid and the mucosal irritation it causes, stretching of the upper duodenum and presence of protein breakdown products (peptides). The presence of HCL, fat and peptides also cause the release of two additional hormones: secretin and cholecystokinin (CCK). One can therefore see how important stomach acid is for the digestive process.
Secretin causes the release of very alkaline sodium and potassium bicarbonate from the pancreas. This neutralizes stomach acid and provides the required alkaline conditions in the small intestine necessary for the continuation of digestion. This also causes a reflex to slow stomach emptying so the proper pH can be maintained.
Fat and protein in the small intestine stimulate the release of CCK, which travels to the pancreas and causes the release of pancreatic enzymes that digest carbohydrate, protein and fat. Similar to the inactive pepsinogen in the stomach, the pancreatic digestive enzymes are also secreted in their inactive form. In the duodenum however, they are activated by an alkaline environment, just the opposite of the stomach, which requires acid to activate pepsinogen.
Fat digestion is a little more complicated. The liver produces 600-1200ml. of bile each day. Bile contains acids that help emulsify fat and turn it into small particles (chylomicrons) that can be further digested by lipase enzymes. Bile acids also aid in transportation of the digested fat through the intestinal mucosal membranes in particles called micelles. Without bile acids, half of the fat is undigested and lost in the stool. Bile also aids in the excretion of excess cholesterol, bilirubin (the end product of red blood cell breakdown) and fat-soluble toxins. Release of bile from the gall bladder is stimulated by CCK.
There are many things that can and do go wrong, and it often starts in the stomach. Low stomach acid causes issues that continue in the small intestine. Lack of acid leads to poorly digested food to be dumped into the duodenum. Since the conditions are not acid but alkaline, this sets up a situation where secretin and CCK stimulation may be reduced. Any bicarbonate released makes the conditions even more alkaline. Decreased amounts of digestive enzymes are released. Stimulation to the gall bladder is reduced.
Low stomach acid causes failure of sterilization of food, which contains many bacteria. This, along with too alkaline conditions set the stage for overgrowth of unfriendly bacteria in the small intestine, which is normally host to the friendly, protective lactobacillus bacteria. This also sets the stage for other pathological bacteria, parasites and yeast (Candida) to overproduce.
This is called dysbiosis and can lead to: inflammation, production of numerous toxins, reduce the production of short chain fatty acids by beneficial bacteria, thereby depriving the intestinal mucosal cells of their primary energy source; reduced production of Vitamin K and some B complex vitamins by friendly bacteria, cause irritable bowel syndrome, hydrogenate essential polyunsaturated fatty acids, block absorption of essential minerals, use essential amino acids leading to deficiencies, turn essential amino acids into toxic products that are absorbed and must be detoxified and excreted, increase the toxic burden of the body causing stress to the liver and kidneys, increase oxidative damage, interfere with the breakdown of bile acids and estrogens increasing the risk for certain cancers, increase the pH of the stool which increases the risk for colon cancer, cause toxic gasses methane and hydrogen sulfate to be produced, overstress the normal GI immune system and eventually reduce Secretory IgA, cause the GI mucosal tight cell junctions to become leaky, leading to “Leaky Gut Syndrome” which increases the risk for food allergies and autoimmune disorders, etc, etc.
Some of the common causes of dysbiosis, aside from hypochlorhydria include: repeat antibiotic therapy, toxic chemicals and heavy metals, exposure to pathogens and parasites, pancreatic insufficiency, slow bowel transit time (often caused by a low fiber diet), poor immune function, poor diet leading to multiple nutritional deficiencies, excess intake of sugar, refined carbohydrates, junk food, food allergies, (especially gluten and dairy products), sodas and alcohol.
Common signs and symptoms include: diarrhea or constipation, excess gas, cramping, bad breath, bloating, weight gain, allergies, sinusitis and asthma, headaches, acne, dermatitis, nervous system problems, autoimmune disorders, fibromyalgia, chronic fatigue, smelly stools, stools that float, gall bladder attacks, easy bruising and dozens of others.
There are lab tests called Advanced Functional Diagnostic Medicine tests that include comprehensive digestive stool analysis (CDSA) testing that will look for overgrowth of normal intestinal flora, check for pathological bacteria, parasites and fungal infections assess pancreatic and gall bladder function and look for bacterial toxic byproducts. A thorough Functional Medicine GI evaluation includes the CDSA, food allergy testing, Heidelberg Gastric pH Analysis and GI permeability (also called Leaky Gut) test. You may wish to consider having one or more of these tests performed if you have signs and symptoms of small intestinal problems