62 Organic Acids Profile

Citric acid cycle intermediates appear in urine when mitochondrial enzyme activity is limited by substrate availability, cofactor deficiency, or genetic variants affecting cycle flux. Elevated urinary concentrations of specific intermediates can reflect bottlenecks at individual enzymatic steps, while global elevation may indicate systemic oxidative stress or vitamin B insufficiency affecting multiple dehydrogenases.

Patterns of citric acid cycle metabolites guide assessment of mitochondrial function and can prompt targeted repletion of cofactors (B vitamins, magnesium, CoQ10). These markers are exploratory tools in functional medicine rather than diagnostic criteria for primary mitochondrial disease.

Homovanillate is the principal urinary metabolite of dopamine, vanillylmandelate of noradrenaline and adrenaline, and 5-hydroxyindoleacetate of serotonin. These metabolites reflect whole-body turnover of monoamine neurotransmitters, influenced by synthesis rate, synaptic activity, and enzymatic degradation by monoamine oxidase and catechol-O-methyltransferase.

Urinary neurotransmitter metabolites are used in functional practice to infer monoamine status and guide amino-acid or cofactor interventions. Low HVA or 5-HIAA may suggest inadequate precursor supply or cofactor deficiency, while very high VMA can reflect sympathetic activation or, rarely, catecholamine-secreting tumours. These are screening-level markers, not diagnostic for primary neuropsychiatric or neuroendocrine disease.

These metabolites arise from bacterial metabolism of dietary substrates and host-derived compounds in the gastrointestinal tract. Hippurate reflects benzoate detoxification and microbial phenolic metabolism; phenylacetate and phenylpropionate derive from bacterial fermentation of phenylalanine and tyrosine; indican is a urinary marker of indole produced from tryptophan by certain gut bacteria; D-arabinitol and D-lactate are products of yeast and some bacterial overgrowth.

Elevated gut microbial metabolites are interpreted as indirect markers of dysbiosis, small intestinal bacterial or fungal overgrowth, or altered intestinal permeability. They inform functional interventions (dietary modification, antimicrobials, probiotics) but are not validated diagnostic criteria for specific gastrointestinal disorders.

D-arabinitol is a five-carbon sugar alcohol produced by Candida and other yeasts; tartarate and citramalate are additional fungal metabolites that may appear in urine when yeast populations are elevated. These metabolites are not normally present at high concentrations in human metabolism.

Urinary yeast metabolites are used in functional medicine as indirect markers of intestinal or systemic yeast overgrowth. Elevation prompts consideration of antifungal therapy and dietary carbohydrate restriction, but these markers are exploratory and have not been validated against culture-based or molecular diagnostics for Candida overgrowth.

Oxalate is an end product of glyoxylate metabolism and ascorbate degradation, and is also absorbed from dietary sources (spinach, rhubarb, nuts, tea). Endogenous synthesis is normally limited by hepatic alanine-glyoxylate aminotransferase; genetic deficiency of this enzyme causes primary hyperoxaluria. Elevated urinary oxalate can also reflect enteric hyperabsorption (in fat malabsorption or after bariatric surgery), high dietary intake, or vitamin B6 deficiency.

Urinary oxalate is measured to assess risk of calcium oxalate nephrolithiasis and to screen for primary or secondary hyperoxaluria. In functional practice it guides dietary oxalate restriction, correction of fat malabsorption, and repletion of pyridoxine and probiotics that degrade oxalate.

Methylmalonate accumulates when vitamin B12 or the adenosylcobalamin cofactor is insufficient for methylmalonyl-CoA mutase. Formiminoglutamate (FIGLU) accumulates in folate deficiency, when formimino transfer to tetrahydrofolate is impaired. Kynurenate and xanthurenate are tryptophan metabolites elevated in vitamin B6 deficiency, which impairs kynureninase and kynurenine aminotransferase. Pyridoxate is a urinary form of vitamin B6.

Organic-acid assessment of vitamin status complements serum micronutrient testing by revealing functional intracellular deficiency. Elevated methylmalonate prompts B12 repletion; elevated FIGLU suggests folate insufficiency; elevated kynurenate and xanthurenate indicate B6 deficiency. These markers guide targeted supplementation in functional and integrative practice.

Adipate, suberate, and sebacate are medium- and long-chain dicarboxylic acids formed by omega-oxidation of fatty acids when mitochondrial beta-oxidation is impaired or overwhelmed. Ethylmalonate can accumulate in disorders of short-chain acyl-CoA dehydrogenase or in secondary inhibition of beta-oxidation. Dicarboxylic aciduria reflects reliance on peroxisomal and microsomal omega-oxidation pathways.

Elevated dicarboxylic acids suggest impaired fatty acid oxidation due to carnitine deficiency, riboflavin insufficiency (required for acyl-CoA dehydrogenases), or inherited defects of beta-oxidation enzymes. In functional practice these markers prompt carnitine and B vitamin repletion; in paediatric or acute settings they raise suspicion of inborn errors of metabolism.

Beta-hydroxybutyrate and acetoacetate are ketone bodies produced by hepatic fatty acid oxidation during fasting, low-carbohydrate diets, or insulin deficiency. Pyruvate and lactate are glycolytic intermediates; the lactate:pyruvate ratio reflects cytosolic redox state. Elevated lactate with normal pyruvate (high ratio) suggests mitochondrial dysfunction; elevated pyruvate with proportional lactate may reflect high glycolytic flux or thiamine deficiency.

Urinary ketones confirm nutritional or pathological ketosis. The lactate:pyruvate ratio is an exploratory marker of mitochondrial function in functional medicine. Persistent ketonuria in a non-fasting, non-ketogenic individual warrants evaluation for diabetes or an inborn error of metabolism.

Glucarate is a marker of hepatic cytochrome P450 induction and glucuronidation capacity; elevated urinary glucarate reflects upregulation of Phase I and II detoxification, often in response to xenobiotic or endobiotic load. Sulfate excretion reflects sulphation capacity, important for detoxifying phenols and steroid hormones. Pyroglutamate may accumulate when glutathione synthesis is impaired or demand is high. Orotate accumulates in urea cycle dysfunction or when mitochondrial carbamoyl phosphate is diverted to pyrimidine synthesis.

These markers are used in functional medicine to assess hepatic detoxification capacity and oxidative stress. Low sulfate or high pyroglutamate may prompt supplementation with sulphur amino acids, N-acetylcysteine, or glycine. Elevated orotate is a functional clue to urea cycle stress or arginine insufficiency, though primary urea cycle defects present with hyperammonaemia.