The digestive tract of man starts in the mouth. The lips, the teeth and the tongue play an important role in the mastication and the softening of the food. Digestion commences in the mouth with the help of the saliva. The food, after due mastication is swallowed whence it enters the oesophagus (or food pipe). The food pipe empties into the stomach. The food in the stomach is acted upon by gastric acid and enzymes which help in digesting the food to its more basic constituents. The continuous churning of the stomach further helps in breaking down the food. From the stomach the food enters the intestines which are the longest part of the gastro-intestinal tract. Here various enzymes complete the digestive processes and absorption of the various elements of the food begins. What is undigested and unabsorbed enters the colon (large intestine). Here the faeces are formed which are gradually taken upto the rectum and anal canal and egested at periodic intervals (Refer figs. I and 2 below for anatomical topography) .

Fig. 1

Fig. 2

Let us now consider the advantages of a vegetarian diet in relation to each of the parts of the gastro-intestinal tract.

1. Vegetarian food being high in its fibre content increases the flow of saliva which enhances digestion and protects the teeth from caries.
2. Cancer of the oesophagus is less common in vegetarians. This is because vegetarian foods like fresh fruit, vegetables, especially amla and citrus fruits contain large doses of vitamin C which has a protective action against malignant disease (cancer).
3. Hiatus hernia which occurs at the junction of the oesophagus and the stomach is less common in vegetarians. Though the cause of this phenomenon is unknown, it is postulated that, vegetarian food, particularly in the natural form, contains very little fat. The fat when present in the diet in excess delays emptying time of the stomach. This leads to pressure on the diaphragm which causes the hiatus hernia.
4. By virtue of the high vitamin C and fibre content the vegetarian food offers protection from stomach malignancy.

5. The intestines are the home of many parasites. The longest of them—taenia saginata and taenia solium (Fig alongside) are found almost exclusively in non-vegetarians, especially in those who eat beef and pork. These worms are almost never found in vegetarians.

6. There are clinical observations that suggest that appendicitis (attack of inflammation of the appendix) is less common in vegetarians.
7. The large intestine (the colon) is most susceptible to the kind of food eaten by us.
   The advantages of a vegetarian diet have been observed in following diseases of the colon:

Constipation

The larger undigestible matter present in fruits and vegetables provides bulk which enhances the forward passage of undigested waste matter from the caecum to the rectum and anal canal. It also reduces the transit time from caecum to rectum. This prevents stasis of poisonous end-products of digestion and resulting diseases of the colon. Thus, while non-vegetarians pass small stools (on an average 100 gm), the vegetarians pass large bulky stools (on an average 300 gm). Also vegetarians pass less foul smelling stools. A few years ago, in my book on 'Common Chronic Disease Patterns in the Arabian Gulf, Saudi Arabia and Yemen', I mentioned that constipation is extremely common in the Arab popula tion. It has been noticed time and again that when these patients are given more vegetables and fruits (in addition to plenty of water to drink), their bowels move freely and they are relieved of their constipation.

Diverticulosis of the Colon

In elderly subjects the incidence of constipation increases markedly due to the development of the above condition. Fig. alongside shows the small pouches looking like pseudopodia which appear on different sides of the colon. Not only do these pouches make the colon very sluggish, but they can get inflamed like the appendix or can bleed like an ulcer. The modern refined and non-vegetarian diet is responsible for this disease. The reduced faecal bulk causes narrowing of the colonic lumen and an increase in intraluminal pressure. This results in protrusion of these pouches known as diverticula. Diverticula may also develop due to the attempts of the proximal colon to overcome obstruction caused by the segmented and narrowed distal colon. Owing to the high fibre content of the vegetarian food, this disease is infrequent in a vegetarian population.

Irritable Bowel Syndrome

This illness is the most common cause of bowel irregularities and colonic gripes. Incidentally it is less frequent in vegetarians owing to the high fibre content of such a diet.

Chronic Ulcerative Colitis

Unlike amoebiasis and giardiasis which are easily treated with drugs, ulcerative colitis is a 'lifelong bloody dysentery'. The incidence of this disease is much less in vegetarians because of the high fibre content.

Cancer of the Colon

It has been proved all over the world that the incidence of the cancer of the colon is very low in vegetarians. It is postulated that the high fibre content of pulses, cereals, vegetables and fruits increases the amount of faeces and reduces the transit time through the colon. As mentioned earlier, the latter reduces the exposure to carcinogens responsible for the development of the cancer of the colon. These substances include tryptophane, tyrosine, methionine, basic amino acids, cholesterol and bile acids. The bile acids are the most important carcinogens. A number of epiderniological studies have shown and several authors have found a significant relationship between the faecal bile acid concentration and colonic cancer.

8. Rectum and anal canal—The diseases of the terminal end of the gastrointestinal tract e.g. fissure and piles are abundant in the normal population. In fact, the incidence of these diseases is highest in the Arab population as described by me in my book on Arab diseases. The fact is that both are related to underlying severe constipation. The straining done to expel the hard stools from the rectum and anal canal, "keeps up" the piles and the fissures.
   In the medical world, it is a very common observation that these diseases are much less common in vegetarians. This seems to be related to the low incidence of constipation amongst vegetarians.

9. The liver and the gallbladder are also affected by the vegetarian diet. Fig. alongside shows the presence of stones in the gall-bladder which can occur in as much as 10% of the population above the age of 70 years. It is interesting to note that the incidence of gall-stones in vegetarians is significantly less. The high fibre content of the vegetarian diet causes reduced deoxycholate absorption which in turn increases the synthesis of chenodeoxycholate. The latter affects the cholesterol saturation of the bile resulting in less stone formation. In fact patients having gall-stones are prescribed high fibre vegetarian diets in order to reduce further gall-stone formation.

   
   Liver is discussed in a separate chapter.

10. Pancreas—Pancreatic malignancies are known to be less common in vegetarians.

All-in-all it appears that vegetarian food is beneficial in prevention as well as in the management of most of the gastro-intestinal diseases.

REFERENCES

1. Bennion LJ, Grundy SM. Risk factors for the development of cholelithiasis in man. N Engl J Med 1978; 299:1221-7.
2. Pixley F. Wilson D, McPherson K, Mann 1. Effect of vegetarianism on developmenl of gallstones in women. Br Med J 1985; 291:11-2.
3. Gear JSS. Warc A, Fursdon P. et al. Symptomless divenicular disease and intake of dietary fiber. Lancet 1979, 1:511-4.
4. Ornstein MH, Littlewood ER, Baird IM, Fowler J. Nonh WRS, Cox AG. Are fibre supplements really necessary in divenicular disease of the colon ? A controlled clinical trial. Br Med J 1981; 2S2:1353-6.
5. Burkitt DP. Epidemiology of cancer of the colon and rectum. Cancer 1971; 28:3-13.
6. Bingham SA, Williams DRR, Cole TJ, James WPT. Dietary fibre consumption and regional large bowel cancer monality in Britain. Br J Cancer 1979; 40:456-63.
7. Graham S. Dayal H. Swanson M, et al. Diet in the epidemiology of cancer of the colon and rectum. JNCI 1978; 61:790-814.
8. Glober GA, Nomura A. Kamiyama S~ Shimada A, Abba BC. Bowel transit time and stool weight in populations with different colon cancer risks. Lancet 1977; 2:110-1.
9. Rider A, Anhus RS, Calkins BM, Nair PP, Diet, nutrition intake and metabolism in populations at high and low risk for colon cancer; selected biochemical parametcrs in blood and urinc. Am J Clin Nutr 1984; 40:917-20.
10. Turnbull GK, Lennard-Jones JE, Bartraum CI. Failure of rectal expulsion as a cause of constipation: Why fiber and laxatives sometimes fail. Lancet 1986; I :767-9.
11. Preston DM, Lennard-Jones JE. Severe chronic constipation of young women. Idiopathic slow transit constipation. Gut 1986; 27:41-8.
12. J.F. Fraumeni, "Cancers of the Pancreas and Biliary Tract: Epidemiological Considerations", Cancer Research 1975: 35:343.
13. Pixley F. et al. Effect of vegetarianism on developmcnt of gall stones in women. Br. Med. J (Clin. Res) 1985 Jul 6, 291 (6487):11-2.
14. Kapoor O.P., Common chronic disease patterns in Arabian Gulf, Saudi Arabia and Yemen. S.S. Publishers Bombay 1983, Page 23.