Formation of carbon dioxide from ascorbate in man.

Area of Science:

• Biochemistry
• Human Physiology
• Nutritional Science

Background:

• Ascorbic acid (vitamin C) is an essential nutrient with various physiological roles.
• Understanding the metabolic fate of ascorbic acid is crucial for determining optimal intake and bioavailability.
• Previous research has not fully elucidated the degradation pathways of high-dose ascorbic acid in the human intestine.

Purpose of the Study:

• To investigate the metabolic fate of 1-14C-labelled ascorbic acid in humans.
• To determine if ascorbic acid degradation occurs presystemically in the intestine.
• To quantify the recovery of labelled ascorbic acid as carbon dioxide in breath.

Main Methods:

• Volunteers received daily doses of ascorbic acid for 3 weeks.
• A tracer dose of 1-14C-labelled ascorbic acid was administered with varying amounts of unlabeled ascorbic acid (90-1000 mg).
• Carbon dioxide in breath was collected and quantified to measure the recovery of the 14C label.

Main Results:

• Carbon dioxide was recovered from breath in all participants receiving 180 mg or more of unlabeled ascorbic acid.
• The percentage of the 14C dose recovered as carbon dioxide ranged from 1% to over 30%.
• A positive correlation was observed between the carrier dose of ascorbic acid and the amount of 14C recovered as carbon dioxide.

Conclusions:

• The formation of carbon dioxide from ascorbic acid suggests a presystemic degradation pathway in the intestine.
• Microbiological or chemical degradation of ascorbic acid in the gastrointestinal tract is a likely mechanism.
• These findings indicate that high doses of ascorbic acid may undergo significant intestinal breakdown, impacting its bioavailability.