Stomach pH Problems
The stomach juices are acidic (low pH) due to the presence of gastric acid. There are various ways in which the stomach pH can be disrupted, mainly due to the loss of acid-producing cells, disturbances in the secretory function of the acid-producing cells or the use of medication that hampers acid production. As mentioned, this acidity is necessary for the activation of pepsin. Therefore pepsin levels are low since pepsinogen is not activated.
In chronic H.pylori infection, the chemicals responsible for promoting inflammation can impair the secretory function of the acid-producing cells, although it may not be damaged or destroyed. Acid-suppressing drugs like proton pump inhibitors (PPIs), which are commonly used to treat conditions like gastritis and peptic ulcers, can also affect stomach pH due to the lower than normal levels of stomach acid.
While aging, chewing can become more difficult, and less efficient.
Chewing is important because it breaks down food and adds enzymes and liquid so that stomach acid and intestinal enzymes can better break it down. When swallowing larger pieces of food without chewing properly, it takes about 50 to 100 percent longer for it reaches to the stomach because of the esophagus, contract less forcefully while aging. A serious problem can be hypertrophic gastritis (reduced production of stomach acid) or atrophic gastritis (the absence of stomach acid).
Too little stomach acid results in decreased vitamin B12 absorption. A deficiency of vitamin B12 in the bloodstream and tissues may lead to pernicious anemia and irreversible nervous-system impairment and may contribute to high levels of homocysteine in the blood. High homocysteine is one of the risk factors for heart disease.People over age 60 have a greater risk of developing gallstones, the narrowing of the bile duct at the opening of the intestine is a risk factor. A high (animal) fat diet brings a greater risk. Upon digestion of fat bile is needed, a substance made by the liver and stored in the gallbladder. Gallstones form when liquid stored in the gallbladder hardens into the rock-hard material. The stones form when the amount of cholesterol or bilirubin in the bile is high.
With aging the gut — particularly the colon — becomes sluggish and less toned. One in three people age 60 or older have diverticula (Diverticulosis is the condition of having multiple pouches and colon (diverticula) in the colon that are not inflamed. These are out pockets of the colonic mucosa and submucosa through weaknesses of muscle layers in the colon wall.) which are outpouchings in the lining of the large intestine. These pouches are the result of increased pressure within the intestine caused by decreased muscle tone. In addition, when the gut gets sluggish, the individual becomes more vulnerable to constipation. Lifestyle is one of the major causes of this problem.
The liver is the largest internal organ, weighing in at about 1.44–1.66 kg. But it gets smaller with time, beginning around age 50. The liver’s shrinkage begins at the same time that body weight and muscle mass start their decline. However, in the very old, the liver becomes disproportionately small. Having less liver tissue and decreased blood flow to this organ means that the body may handle certain medications differently.
The large intestine or colon is shorter than the small intestine but has a larger diameter. The length of the colon is approximately 1,4 – 1,8 meter. Its largest diameter is at the cecum (7.5 cm) and narrowest in the sigmoid (2.5 cm). The colon has the function of absorption of water and electrolytes and storing waste until it can be expelled. It is responsible for maintaining water balance and absorption of vitamins. The mixture of remaining food and intestinal juices is called chyme. It is devoid of almost all nutrients and water; it consists of primarily the undigested food with some amount of water and electrolytes.
The lining of the colon is different from the small intestine in that there exists a large number of mucous cells that do not secrete enzymes but mucus. The mucus helps to protect the wall from the bacterial fermentation inside. About 1.5 L of liquid digestive contents, chyme, pass into the colon. The colon is responsible for absorbing and recycling the great majority of this liquid.
Completing the process of digestion that largely takes place in the small intestine. It takes nearly 24 to 30 hours to complete the digestive process. Further digestion or breaking down of nutrients does not take place there but it helps by absorbing water and making the stools solid.
Absorption of vitamins
The large intestine helps in absorption of vitamins made by bacteria that normally live in the large intestine. There are over 700 – 1000 species of bacteria that perform a variety of functions. These commensal bacteria break down the undigested polysaccharides or fibers in diet into short-chain fatty acids. These can be absorbed by the large intestine by passive diffusion. The bacteria also produce gas (flatus), which is a mixture of nitrogen and carbon dioxide, with small amounts of the gases hydrogen, methane, and hydrogen sulfide. These result from the bacterial fermentation of undigested polysaccharides.
These bacteria also produce vitamins. The most important of these is Vitamin K and Biotin (a B vitamin). When the vitamin intake in the diet is low, this can be a source of these vitamins. A person who depends on absorption of vitamins formed by bacteria in the large intestine may become vitamin deficient if treated with drugs like antibiotics that kill the commensal bacteria. While chyme moves through the large intestine, bacteria digest substances in the chyme that is not digestible by the human digestive system. Bacterial fermentation converts the chyme into feces and releases vitamins including vitamins K, B1, B2, B6, B12, and biotin. Vitamin K is almost exclusively produced by the gut bacteria and is essential in the proper clotting of blood.
The movement of gas through the intestines produces the gurgling sounds known as borborygmi. In the resting state, there are usually about 200 ml of gas in the gastrointestinal tract. Its composition varies: between 20 and 90 percent nitrogen, up to 10 percent oxygen, up to 50 percent hydrogen, up to 10 percent methane, and between 10 and 30 percent carbon dioxide. Most of the air that people swallow, while talking and eating in particular, is either regurgitated (as in belching) or absorbed in the stomach.
High levels of carbon dioxide in rectal flatus reflect bacterial activity in the colon. Methane cannot be produced by any cell and is entirely the result of bacteria’s acting on fermentable dietary residues in the colon, although there appears to be a familial factor involved in this, as not everyone can generate methane.
In the colon, bacterial production of hydrogen is markedly elevated when the diet contains an excess of vegetable saccharides. This is particularly noticeable after consuming beans, for example. Gas is more often responsible for the buoyancy of stools than is excessive residual fat in malabsorption states. The gradient between the partial pressures (or the pressure exerted by each gas in a mixture of gases) of particular gases in the intestinal lumen and the partial pressures of gases in the circulating blood determines the direction of movement of gases.
Thus, because oxygen tends to be under a low pressure in the colon, it diffuses out from the blood into the intestine. The diffusion of nitrogen from the blood into the intestine occurs because a gradient is established by the carbon dioxide, methane, and hydrogen that result from metabolic activities of the commensal bacteria; the partial pressure contributed by nitrogen in the colon is lowered, stimulating nitrogen to enter the intestine from the blood.
In areas where lactase, the enzyme that breaks down lactose (milk sugar), is missing from the group of disaccharidases of the small intestine, lactose passes into the colon undigested. In a lactase-deficient person, the unhydrolyzed lactose enters the colon, where the amount of lactose normally present in a glass of milk is capable of liberating, after bacterial fermentation, the equivalent of two to four cups (500–1,000 ml) of gas (hydrogen). About 15 percent of the gas diffuses back into the blood, with the rest passing as flatus.
Hydrogen generated in the colon is partly absorbed, passes in the circulating blood to the lungs, and diffuses into the respiratory passages, where its presence can be easily determined. The time taken for hydrogen to appear in the breath after ingestion of a standard load of glucose or lactose is used to determine whether the upper area of the gastrointestinal tract is colonized by bacteria. Hydrogen that appears within 30 minutes of the ingestion of the sugar load suggests heavy colonization of the small intestine.
The rectum enlarges as people age, and increased storage of stool in the rectum means that older people often need to have larger volumes of stool in their rectum in order to feel the urge to defecate. The increased rectal volume also allows hard stool to become impacted.
Other common factors in older people that lead to constipation include increased use of constipating drugs, a low-fiber diet, coexisting medical conditions (such as diabetes), and reduced physical activity.
BASIC ANATOMY OF THE COLON
The colon is divided into four sections – the ascending colon, the transverse colon, the descending colon, and the sigmoid colon. The colon lies in the abdominal cavity and behind it. The left side of the colon is involved in absorption while the right side is involved with storing feces.
The rectum is 10 cm in length in the adult. It starts at the peritoneal reflexion and follows the curve of the sacrum ending at the anal canal. The anal canal is 5 cm in length in the adult, has discrete upper and lower demarcations.
Over the surface of the large intestine are longitudinal muscle fibers called taeniae coli, each about 5 mm wide. There are three bands and they start at the base of the appendix and extend from the cecum to the rectum. There are sacculations called haustra that are characteristic features of the large intestine, and distinguish it from the rest of the intestines. There is a large amount of lymphoid tissue that helps in maintaining an immune barrier. Macrophages or immune cells lie at the subepithelial layer.
The large intestine, particularly the appendix, is a confluence of several lymphoid tissues. These play an important role in immunity. The lymphoid tissues of the large intestine also help in the production of antibodies and cross-reactive antibodies. These antibodies are produced by the immune system against the normal commensal bacteria but may also be active against related harmful bacteria and thus prevent infections.
BACTERIA IN THE COLON
The bacteria in the colon are capable of digesting small amounts of cellulose. Substances formed as a result of bacteria activity include vitamin K, vitamin B12, thiamin, and riboflavin.
During its passage through the large intestine, digested material by-products are converted to feces upon fermentation and reaction with the gut flora. This waste material is received by the ascending colon which reabsorbs excess water and eventually pushes the semi-solid matter to the descending colon. Here, the gut flora breaks down fiber for sustaining itself and releases acetate, propionate, and butyrate. These are absorbed by the cell lining for nourishment. From the colon, the stool passes to the rectum to be discharged from the body.
Diseases and conditions that affect the colon and the digestive system and which are often age related (this is a short list):olon Cancer: Acid Reflux (GERD)
Inflammatory Bowel Disease Irritable Bowel Syndrome
Lactose Intolerance Stomach Ulcers
Tapeworms Ulcerative Colitis
Many people use colon cleanses as a means to keep the colon healthy. This process includes taking laxatives, teas, powders or supplements, using enemas, or getting colonic irrigation (colon hydrotherapy) to flush out the colon. There can be side effects of cleansing, and some practices can even be dangerous. Doctors have varied opinions on cleansing. The colon’s very function is to remove toxins.