Dietary fibre-rich resistant starches promote ammonia detoxification in the human colon as measured by lactose-[¹⁵N₂]ureide

Abstract

Three resistant starches (RSs), namely fibre of potatoes (FP), wrinkle pea starch (WPS), and high amylose maize starch (HAMS) with different dietary fibre contents, were supplemented in adults to evaluate their effects on urinary nitrogen and ammonia excretion as well as on faecal nitrogen excretion by means of lactose-[¹⁵N₂]ureide (¹⁵N-LU) degradation. Twenty subjects received a regular diet either without or with the supplementation of FP, WPS, and HAMS in a randomized order. After administration of ¹⁵N-LU, urine and faeces were collected over 48 and 72 h, respectively, whereas blood was collected after 6 h. The ¹⁵N-abundances were measured by isotope ratio mass spectrometry. In comparison to the dry run, supplementation with RS significantly lowered renal ¹⁵N-excretion (dry run: 43.2 %, FP: 34.6 %, WPS: 37.9 %, HAMS: 36.4 %) as well as the corresponding ¹⁵NH₃-excretion (dry run: 0.08 %, FP: 0.06 %, HAMS: 0.05 %), clearly indicating a reduced colonic nitrogen generation at high dietary fibre intake.

Keywords:

• colon metabolism
• dietary fibre
• isotope application in medicine
• lactose-[¹⁵N₂]ureide
• men
• nitrogen-15
• resistant starch
• stable isotope tracer techniques

Disclosure statement

No potential conflict of interest was reported by the author.