Guar gum and digestion

[Guest guest]

Hi All,

The effects of guar gum depend on caloric content of food for

altering

digestion, it seem from the pdf-available below.

>>>Digestive Diseases and Sciences, Vol. 42, No. 8 (August 1997)

Effect of Viscous Fiber (Guar) on

Postprandial Motor Activity in Human Small Bowel

J.v. SCHONFELD, D.F. EVANS, and D.L. WINGATE

Both caloric value and chemical compositi on of a meal have been

shown to regulate

postprandial small bowel motility in dog. In the same species,

duration of and contractil e

activity within the postprandial period also depends on mean

viscosity. It is unknown,

however, whether meal viscosity and ®ber content also regulate small

bowel motor activity in

man. In human volunteers, we therefore studied the effect of guar gum

on small bowel motor

response to liquid and solid meals. Twenty-six prolonged ambulatory

small bowel manometry

studies were performed in 12 volunteers. A total of 620 hr of

recording were analyzed visually

for phase III of the MMC and a validated computer program calculated

the incidence and

amplitude of contractio ns after ingestion of water (300 ml), a pure

glucose drink (300 ml/330

kcal) or a solid meal (530 kcal) with and without 5 g of guar gum.

Addition of 5 g of guar gum

did not signi®cantly delay reappearanc e of phase III after ingestion

of water (59 611 vs

106 621 min; P 50.09). However, guar gum signi® cantly prolonged

duration of postprandial

motility pattern both after the glucose drink (123 619 vs 199 624

min; P ,0.05) and after

the solid meal (310 692vs 419 622 min; P 50.005). Contracti le

activity during these periods

was not affected by guar gum. This was true for mean incidence of

contractio ns after water

(1.9 60.3 vs 1.8 60.5 min21), after the glucose drink (1.6 60.4 vs

1.7 60.3 min21) and after

the solid meal (2.4 60.4 vs 2.6 60.4 min 21 ). Likewise, mean

amplitude of contracti ons was

not affected by guar gum after water (22.8 61.4 vs 20.9 61.9 mm Hg),

after the glucose drink

(20.5 61.4 vs 21.3 61.2), and after the solid meal (20.3 61.5 vs 21.5

61.6 mm Hg). Thus

a guar gum-induced increase in chyme viscosity markedly prolonged

duration of postprandial

motor activity in the human small bowel. Contracti le activity within

the postprandi al period,

however, was not affected. We suggest that the postprandial motility

pattern persisted longer

after the more viscous meals, because gastric emptying and intestinal

transit were delayed by

guar gum. We conclude that it is essential to de®ne meal viscosity

and ®ber content when

studying postprandi al small bowel motility.

KEY WORDS: postprandial motility; interdigestive motility; guar gum;

viscosity; ®ber; human; small bowel.

......

DISCUSSION

Guar gum, a galactomannan extract of the Indian

cluster bean, is a high-molecular-weight polysaccha-ride,

which is not digested or absorbed in the stomach

or small bowel. Although it usually goes unnoticed,

the food industry uses it widely as a thickening agent,

emulsion stabilizer, and suspending agent, at least in

the UK. In clinical practice it is sometimes prescribed

as an adjunct in the treatment of diabetes and hyper-cholesterolemia,

or in patients with dumping syn-drome.

We studied the effect of 5 g of guar gum, a

standard therapeut ic dose, in order to learn how

chyme viscosity affects jejunal motor function in man.

Furthermore, it was unknown how dietary ®bers af-fect

small bowel motor activity in man, and guar gum,

although not a true ®ber by de®nition, is considered

part of the dietary ®ber complex (15).

This study demonstrat es that addition of guar gum

to nutrient drinks and solid meals markedly prolongs

duration of the postprandi al motility pattern. Mean

duration of postprandial motility was prolonged from

2 to 3 hr after the glucose drink and from 5 to 7 hr

after the solid meal with guar gum. As a phase III,

which de®nes the return to interdigest ive motility,

was not recorded after six of 10 solid meals with guar,

the true time difference for solid meals must be even

greater than the 2-hr increase in mean duration ob-served

in this study. This ®nding con®rms previous

studies, which, however, were all done in animals (10,

11, 16).

Both gastric emptying and intestinal transit have

been shown to correlate with duration of postprandi al

motility (17± 19). As guar gum has been shown to

affect both of these gastrointestinal motor functions

in man and dog (10, 16, 20 ±22), we suggest that guar

gum prolonged the postprandi al period by slowing

gastric emptying and small intestinal transit. Other

factors, however, may also have been relevant, as guar

gum is known to slow digestion and absorption of

nutrients (23). In addition, animal studies by Meyer et

al suggest that guar slows emptying of the liquid part

of a meal, but speeds emptying of particulat e matter.

Thus gastric sieving may be impaired by guar (24, 25).

As guar is known to markedly increase the viscosity

and volume of chyme (16, 24, 25), one would expect

the compound to also affect contractile activity of the

small bowel. However, in our study, both incidence

and amplitude of contracti ons during the postpran-dial

period were similar after meals with and without

guar. This ®nding in humans is in disagreement with

published animal data. Bueno et al reported an in-crease

in frequency and a reduction in amplitude of

contractions in the canine jejunum, when a much

higher dose of guar (30 g) was added to canned food.

In their study the increase in frequency of contrac-tions

was so marked that motility indices were almost

doubled in spite of the reduction in amplitude of

contractions (10). In the same species, and

Bass also observed an increase in jejunal motor ac-tivity,

when they added pectin or psyllium to saline

(11). In pigs, 12 g of guar added to a semisynthetic

diet also increased motility indices, derived from

myoelectrical recordings in stomach, duodenum, and

jejunum (16). Thus the 5 g of guar gum, as used in our

study, may have been too small a dose to affect

contractil e activity of the human small bowel in the

postprandi al period.

We conclude that viscosity and ®ber content of a

meal markedly prolong the postprandi al period in the

human small bowel. Therefore, it is essential to de®ne

these two variables, when studying postprandi al small

bowel motor activity.

Cheers, Al Pater.