How does gravity assist the passage of food through the digestive system?

human digestive system is a single tube

Our entire digestive tract is composed of a single tube running from our mouth to anus. Note that the large intestine resembles a siphon, with the anus being lower in relation to gravity when we are upright and that the small intestine provides positive pressure from the downward flowing stomach contents.

Think about this for a moment. Our intestines consist of a single tube that is compacted and aranged inside our abdomen. When we are sleeping flat, we "almost" cancel out the influence by gravity and how it acts upon our meals and drinks on it's journey through our body, although as we rotate in a flat bed we do make some use of gravity, which undoubtedly helps to move food, albeit more slowly.

When we are inclined in bed, no matter which position we sleep in, gravity is positively acting upon the digestive system by helping to move food more quickly, which helps to prevent constipation and diarrhoea and avoid scybala (Hardened masses of faeces) from causing a blockage in the colon.

IBT has been successful in arresting acute diarrhoea in patients at the end of life with AIDS!

It's not difficult to see how avoiding sleeping for too long in one position and rotating in bed, would accomodate the passage of waste food more effectively in both flat and inclined bed rest.

Keeping food moving is important and more easily accomplished with activity-as we change our posture. This undoubtedly helps our food to navigate the bends in the intestines and bowel. When we are in an inclined bed, bowel movements tend to occur shortly after getting up in the morning and become more regular. This is great news for the lining of the digestive tract, because it is helping to prevent the stagnation and overburden of our intestines with bacteria and decaying, poorly-digested food.

I suspect that bowel cancer may in part, be a complication of a compromised digestive system and it’s reduced movement of foods, when sleeping horizontally and could be helped by avoiding flat bed rest.



Effects of bedrest 2: gastrointestinal, endocrine, renal, reproductive and nervous systems 5 JUNE, 2009

"Exploring what happens to the gastrointestinal, endocrine, renal, reproductive and nervous systems, and processes in the body when a person is confined to bed

Authors:  John Knight, PhD, BSc; Yamni Nigam, PhD, MSc, BSc; Aled Jones, PhD, BN, RN (Adult), RMN; all are lecturers, School of Health Science,

Swansea University.

Gastrointestinal system Bedrest is often associated with a reduced sense of taste, smell and a loss of appetite (Rousseau, 1993; Bortz, 1984).

The resulting drop in food intake leads to progressive disuse of the gastrointestinal (GI) tract. This can have a major impact on gut structure and function, including atrophy of the mucosal lining and shrinkage of glandular structures (Bortz, 1984).

Swallowing is more difficult for people confined to bed and it has been shown that non-viscous substances pass through the oesophagus more slowly when the body is supine (Kaplan, 2005). It also takes longer for food to pass through the stomach – 66% more slowly in recumbent patients than in upright ones (Thomas et al, 2002).

Increased transit times slow the movement of faeces through the colon and rectum, increasing water reabsorption. As a result, stools progressively harden causing constipation, a common problem in patients confined to bed. Constipation is often associated with faecal impaction, which, if severe, may need mechanical intervention for removal. In an upright person, gravity causes stools within the rectum to exert pressure on the anal sphincter, but this effect of gravity is negated in supine patients, reducing the urge to defecate.

The problem of constipation is particularly troublesome in patients confined to bed receiving opioid-based pain relief medications. Drugs such as morphine dramatically slow down gut motility (Jordan, 2008), exacerbating the effects of immobility.

If constipation becomes chronic, the build-up of faecal material can exert significant pressure on the wall of the colon, increasing the chance of diverticuli (Bortz, 1984).

The risk of constipation can be reduced by ensuring that patients get enough dietary fibre, which should help to speed up gut transit times. Patients should also be encouraged to take regular drinks of fresh water, which will be soaked up by fibre within the gut, increasing faecal bulk and softening the stools.

During bedrest, gastric bicarbonate secretion may also decrease (Kaplan, 2005), increasing acidity within the stomach. When patients are in the supine position, these gastric secretions can collect and press against the lower oesophageal (cardiac) sphincter, causing irritation. Patients confined to bed can experience symptoms associated with gastro-oesophageal reflux disease (GORD), such as regurgitation and heartburn. This can be alleviated by using pillows to prop them up after a meal.

This position also encourages the gastric juices to collect in the lower portion of the stomach, reducing the risk of reflux.

Antacid medications can also be given to relieve the sensation of heartburn."