- 4-Hydroxyphenylacetic acid is primarily a tyrosine breakdown product. Acinetobacter, Clostridium, Klebsiella, Pseudomonas, and Proteus act on food high in tyrosine or tyramine (fermented foods, such as sausages, marmite, soybean products, fish sauce, beers, and wine). C. difficile is known to decarboxylate 4-hydroxyphenylacetic acid to produce p-cresol.
- 4-Hydroxyphenylacetic acid is found higher in olives, American cranberries, grape wines; lower in corn, beers, oats, cocoa beans, milk (cow), evening primrose. 4-Hydroxyphenylacetic acid was higher in the urine of those adhering to a Mediterranean diet.
- If elevated, evaluate protein intake, digestion, and gut bacteria. Quercetin has been proposed to reduce radicals of 4-hydroxyphenylacetic acid.
- Though the perfect test for small bowel bacterial overgrowth (SIBO) has yet to be devised, limited research has correlated 4-hydroxyphenylacetic acid with SIBO.
High 4-Hydroxyphenylacetic acid may be associated with small intestinal bacteria overgrowth (SIBO) due to its production by:
- C. difficile
- C. stricklandii
- C. lituseburense
- C. subterminale
- C. putrefaciens
- C. propionicum
C. difficile can be distinguished from the other species by its production of 4-cresol. No other Clostridia species produce 4-cresol.
Elevated values of 4-hydroxyphenylacetic acid are common in:
- Celiac disease
- Cystic fibrosis
- Jejuna web
- Transient lactose intolerance
- Giardia infection
- Ileal resection
- Ileo-colic intersusseception
- Projectile vomiting.
Elevations of 4-hydroxyphenylacetic acid in celiac disease and cystic fibrosis are common enough to suggest that these Clostridia bacteria may play a role in these illnesses.
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