The digestion and absorption of ingested foods is a series of biochemical marvels. Food supplies the body with the raw materials necessary to maintain life, yet is virtually useless to human physiology until acted upon by the myriad of enzymes and chemicals of the digestive system.
FUNCTION & COMPOSITION
In a healthy person, the digestive processes are extremely efficient, with about 90% of the carbohydrate, fat and protein being digested into their component parts in time to be absorbed (2).
Digestion begins in the mouth, where food is crushed, mashed and mixed with saliva. Saliva contains the enzyme amylase, which is involved in the breakdown of starch into simple sugars. The chewed food is then swallowed and propelled down the oesophagus via peristaltic waves. Once in the stomach, the food is thoroughly mixed together and gastric acid and enzymes begin to digest protein. As the ingested food becomes liquified, the pylorus valve relaxes, allowing the thick liquid mass (or chyme) to pass into the small intestine. Once there, the material is changed to a slightly alkaline pH by bile and pancreatic juices, which contain various enzymes and emulsifying agents. As the enzymes do their job, smaller and smaller chemical fragments are liberated from the digestive soup and are absorbed into the bloodstream (1).
The final stage of digestion is where watery material not previously digested enters the large intestine. Water is reabsorbed from the material as it slowly passes through the colon. The colon is home to a large number of bacteria, which along with fat and indigestible fibre constitute the bulk of the faeces. The final step of the digestive process is defaecation achieved by the voluntary contraction of the anal sphincter muscle (1).
COMMON DIGESTIVE COMPLAINTS
Constipation is a common symptom affecting the quality of life of approximately 20% of senior citizens and 10% of all adults. Transit time of food increases from a normal 1 or 2 days up to 5 days when constipated, the length of time involved will vary according to the individual. The most common cause of Constipation is thought to be an insufficient intake of dietary fibre, although water plays an important role in the digestive tract. Stress and emotional upset can influence bowel habits. Establishing a regular toilet routine, drinking more fluid and consuming fibre rich foods should help the condition (6). For short term relief, a standardised extract of Senna supplement may be beneficial. A supplement of L Acidophilus capsules or regular live yoghurt may help to alleviate the condition.
A food Allergy occurs when there is an adverse reaction to the ingestion of a particular food or food component. Food allergies have been implicated in a wide range of medical conditions, affecting virtually every part of the body - from mildly uncomfortable symptoms, such as indigestion and Gastritis, to severe illness, such as Coeliac Disease, Arthritis and chronic Infection. Allergies have also been linked to numerous disorders of the central nervous system (CNS), including Anxiety, Depression and chronic Fatigue (3).
Gallstones are crystallisations of cholesterol and the pigment bilirubin, and are usually about the size of an orange pip. They can cause Inflammation of the gall bladder, which results in symptoms similar to indigestion, especially after a fatty meal. If treatment is necessary, it usually takes the form of drugs that help to dissolve the stone or surgery may be required to remove the gallbladder (6).
To help prevent a gallstone recurring it is important to keep your weight under control and to limit the amount of fatty and sugary foods that are consumed. In addition, Lecithin supplements may have a protective effect as they increase the capacity of bile to solubilise cholesterol (7).
Irritable Bowel Syndrome
Irritable bowel syndrome (IBS) is not a disease but a collection of symptoms. The symptoms experienced can vary and are often linked with varying degrees of Stress, Anxiety and Depression. IBS is characterised by abdominal discomfort, Bloating and wind, together with Diarrhoea and / or Constipation, without a clear physical cause. The primary cause of IBS is thought to be excessive muscle spasms in the large intestine. Other causes include a low fibre diet, food sensitivities, intestinal candidiasis and Stress. Antispasmodics and antidepressants are widely used drugs, though not of proven benefit. Good dietary management may help to relieve some of the symptoms, though cure of the disease is difficult.
A peptic ulcer is usually caused by the erosion of the stomach lining, either because of over acidity or through Infection with bacterium Helicobacter pylori. The symptoms of a peptic ulcer are usually a burning, gnawing Pain in the abdomen together with a loss of appetite, belching and a feeling of nausea (6).
There are a number of lifestyle factors which should be addressed to help promote the healing of an ulcer. Limit tea, coffee and alcohol consumption and most importantly, avoid Smoking. Eat several small meals a day, at regular intervals, rather than two or three large ones. Also, avoid the use of aspirin and non-steroidal anti-inflammatory drugs. Deglycyrrhizinated Liquorice stimulates the body?s normal defence mechanisms against ulcer formation by increasing the quality and quantity of protective substances that line the intestinal tract (8). In addition, the amino acid L-glutamine may be useful as it promotes the healing of peptic ulcers. The suggested intake is 1000mg per day (9).
Anxiety and the stresses and strains of modern living may have a profound affect on the digestive processes. If a person is in a stressed state, the body is programmed to shunt blood away from the digestive tract in favour of the skeletal muscle and brain. Learning to calm the mind and body is extremely important for promoting healthy digestion and may be helped by regular supplementation with a vitamin B complex (3).
With increasing age, the digestive processes gradually slow and become less efficient. In addition, it has been found that vitamin and mineral intake and status are often deficient in elderly subjects, probably as a result of a poor diet and physiological changes to the digestive tract. It is therefore important for the elderly to safeguard their intake of essential nutrients by eating a balanced diet and through regular supplementation with a good quality multivitamin and mineral product (4).
The acid-producing cells in the stomach may secrete too much or too little hydrochloric acid. The optimum pH range of the stomach is 1.5 to 2.5, with hydrochloric acid being the primary stomach acid. Although much is said about over-acidity, a more common cause of indigestion is insufficient gastric secretion (hypochlorhydria) (3).
10 tips for healthy digestion
- Avoid digestive irritants such as spicy foods, alcohol and certain over-the-counter drugs.
- Chew each mouthful of food thoroughly.
- Do not eat meals in front of the television.
- Eating little and often is better than consuming large meals.
- Try not to eat too late in the evening.
- Drink plenty of water each day (the recommended amount is 1.5 litres a day).
- Eat a varied diet, with plenty of fresh fruit and vegetables.
- Avoid over-processed food, it may contain over the daily allowance of salt.
- Ensure that your diet provides between 18-30g of fibre per day.
- Most importantly, enjoy your food!
Maintaining a favourable balance of "friendly" bacteria in the gut is vital to a healthy digestive system. Sometimes this balance can be upset by prescription medication (for example antibiotics, contraceptive pill and steroids), or changes in the diet. Supplements containing L. acidophilus may be chosen to help maintain the balance of bacteria in the gut - providing the ideal environment for digestion and healthy bowel regularity (5).
A variety of Digestive Enzymes are required throughout the digestive tract to aid the breakdown of food into smaller pieces that can be easily absorbed. Supplementation with a comprehensive digestive enzyme supplement will help to ensure optimum levels of these enzymes. Similarly, those who are unable to tolerate dairy products because of an inability to digest the milk sugar lactose may benefit from a lactase supplement.
1. Human Physiology From Cells to Systems, L Sherwood, West Publishing Company, 1993.
2. Nutrition Concepts and Controversies, F. Sizer & E. Whitney, West Publishing Company, 1994.
3. Encyclopaedia of Natural Medicine, Murray & Pizzorno, Little, Brown & C, 1998.
4. Proceedings of the Nutrition Society, 1999, 58:573-578.
5. Microbial Ecology in Health and Disease, 1994, 7:17-25.
6. The BMA Complete Family Health Encyclopaedia, Ed. Dr T. Smith, Dorling Kindersley, 1995.
7. Biochem J. 1996, 318 Pt 1:139-144.
8. The Healing Power of herbs, MT Murray, Prima Publishing, 1995.
9. Nutrition, 1997, 13:7-8:743-747.
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