Clinical Nutrition

Lesson 9:Gastro intestinal tract diseases

Absorptive Studies

Absorptive or lack of absorption of certain nutrients/non nutrients can be studied by this method.

Absorption of fat

A known amount of fat (approximately 80 – 100g) is given orally and the amount excreted in the feces is estimated. The rest is considered to be absorbed. The normal excretion of fat in the feces is 7% of intake or less. Any amount more than this, indicates steatrrhoea.

Absorption of D-Xylose

The absorption of D-Xylose given orally indicates the presence/absence of intestinal diseases. 25g of D-Xylose is given orally. Urine samples are collected for about 5 hours. The five hour urine sample should normally have more than 4.5g of D-Xylose. In intestinal diseases the D-Xylose excretion decreases to less than 3g.