Cellular Micronutrient Assay

Thiamine pyrophosphate is an essential cofactor for enzymes in carbohydrate metabolism and the pentose phosphate pathway. Cellular assays measure the functional capacity of lymphocytes to proliferate in response to mitogenic stimulation when thiamine is the rate-limiting substrate, reflecting intracellular sufficiency rather than serum concentration.

Functional B1 deficiency impairs energy metabolism and is associated with fatigue, neuropathy, and beriberi syndromes. Cellular assessment may detect insufficiency missed by serum thiamine, particularly in chronic illness, alcohol use disorder, and high metabolic demand states.

Riboflavin is the precursor of FAD and FMN, coenzymes in redox reactions across energy metabolism, one-carbon pathways, and antioxidant defence. The assay measures lymphocyte functional response when riboflavin availability limits cellular processes.

Riboflavin insufficiency can impair mitochondrial function, homocysteine metabolism, and glutathione recycling. Functional testing may identify subclinical deficiency in malabsorption, restrictive diets, and genetic polymorphisms affecting flavin metabolism.

Niacin is the precursor of NAD and NADP, coenzymes central to redox metabolism, DNA repair, and cellular signalling. Functional assays assess the capacity of lymphocytes to sustain growth when niacin is limiting.

Niacin deficiency classically causes pellagra but subclinical insufficiency may contribute to fatigue, cognitive dysfunction, and impaired cellular repair. Cellular assays complement urinary metabolite and serum measures in complex cases.

Pantothenic acid is the precursor of coenzyme A, essential for fatty acid synthesis and oxidation, the tricarboxylic acid cycle, and acetylation reactions. The assay measures lymphocyte function when pantothenate is rate-limiting.

Pantothenic acid deficiency is rare but may present with fatigue, paraesthesia, and impaired adrenal steroid synthesis. Functional testing is used in fatigue syndromes and suspected mitochondrial dysfunction where serum levels are uninformative.

Pyridoxal-5'-phosphate is a cofactor for over 100 enzymes, including those in amino acid metabolism, neurotransmitter synthesis, haem synthesis, and one-carbon metabolism. Cellular assays measure functional capacity when B6 is limiting, capturing both supply and the efficiency of conversion to active forms.

Functional B6 insufficiency can impair homocysteine metabolism, immune function, and neurotransmitter synthesis. It is relevant in neuropathy, sideroblastic anaemia, and disorders of tryptophan metabolism, and may be missed by plasma pyridoxal-5'-phosphate alone in inflammatory states.

Biotin is a cofactor for carboxylase enzymes in gluconeogenesis, fatty acid synthesis, and branched-chain amino acid catabolism. Functional assays assess lymphocyte performance when biotin is rate-limiting.

Biotin deficiency causes dermatitis, alopecia, and neurological symptoms. Functional testing is used in suspected deficiency due to malabsorption, biotinidase deficiency, or prolonged anticonvulsant or raw-egg-white consumption, where serum biotin may not reflect intracellular status.

Folate, as tetrahydrofolate and methyl-tetrahydrofolate, is essential for one-carbon metabolism, DNA synthesis, and methylation. Cellular assays measure the functional capacity of lymphocytes to proliferate when folate availability is limiting.

Folate insufficiency causes megaloblastic anaemia, hyperhomocysteinaemia, and neural tube defects. Cellular testing may identify functional deficiency in the setting of normal serum folate, particularly with MTHFR polymorphisms, malabsorption, or medications that impair folate metabolism.

Cobalamin is a cofactor for methionine synthase and methylmalonyl-CoA mutase, linking one-carbon metabolism, methylation, and propionate catabolism. Functional assays assess lymphocyte growth when cobalamin is rate-limiting, integrating absorption, transport, and intracellular conversion to active forms.

Functional B12 deficiency can cause megaloblastic anaemia, neuropathy, and cognitive impairment. Cellular testing may detect insufficiency missed by serum B12, particularly in the presence of transcobalamin polymorphisms, nitrous oxide exposure, or metformin use.

Ascorbic acid is a water-soluble antioxidant and cofactor for hydroxylases in collagen synthesis, carnitine synthesis, and neurotransmitter metabolism. Cellular assays measure functional lymphocyte capacity when ascorbate is rate-limiting.

Vitamin C deficiency causes scurvy but subclinical insufficiency may impair wound healing, immune function, and iron absorption. Functional testing complements plasma ascorbate in malabsorption, chronic illness, smoking, and critical illness where turnover is high.

Vitamin D, as calcitriol, regulates calcium homeostasis, bone metabolism, immune function, and gene transcription through the vitamin D receptor. Cellular assays assess the functional response of lymphocytes to vitamin D signalling, which may diverge from serum 25-hydroxyvitamin D in receptor polymorphisms or inflammatory states.

Functional vitamin D insufficiency is relevant in bone disease, autoimmunity, and immune dysregulation. Cellular testing may identify receptor-level or conversion defects not captured by serum 25(OH)D alone.

Alpha-tocopherol is the principal lipid-soluble antioxidant in cell membranes, protecting polyunsaturated fatty acids from peroxidation. Functional assays measure lymphocyte antioxidant capacity when vitamin E is rate-limiting.

Vitamin E deficiency causes ataxia, neuropathy, and haemolytic anaemia, particularly in fat malabsorption and genetic disorders of tocopherol transport. Cellular testing is used when serum tocopherol is discordant with clinical suspicion or when functional antioxidant capacity is questioned.

Calcium is a ubiquitous intracellular signalling ion and structural component of bone. Cellular assays assess the functional availability of calcium to support lymphocyte activation and proliferation, which can be impaired despite normal serum calcium in states of vitamin D insufficiency or intracellular dysregulation.

Functional calcium insufficiency is relevant in bone health, neuromuscular function, and immune activation. Cellular testing may identify deficits in cellular calcium handling not reflected by serum total or ionised calcium.

Magnesium is a cofactor for over 300 enzymes, including those in ATP synthesis, nucleic acid metabolism, and protein synthesis. The majority of body magnesium is intracellular; serum levels poorly reflect tissue stores. Functional assays measure lymphocyte performance when magnesium is rate-limiting.

Magnesium insufficiency contributes to muscle cramps, arrhythmia, hypertension, insulin resistance, and neuropsychiatric symptoms. Cellular testing may detect functional deficiency missed by serum magnesium, particularly in chronic stress, gastrointestinal loss, or medication use (diuretics, proton pump inhibitors).

Zinc is a cofactor for hundreds of metalloenzymes and a structural component of zinc-finger transcription factors, essential for immune function, protein synthesis, and antioxidant defence. Cellular assays measure functional zinc availability in lymphocytes, which can diverge from serum zinc in inflammatory or catabolic states.

Zinc insufficiency impairs immune function, wound healing, and growth. Functional testing is relevant in malabsorption, chronic infection, acrodermatitis enteropathica, and settings where serum zinc is confounded by acute-phase response or albumin.

Copper is a cofactor for enzymes in iron metabolism (ceruloplasmin), antioxidant defence (superoxide dismutase), and neurotransmitter synthesis. Cellular assays assess functional copper availability in lymphocytes.

Copper deficiency causes anaemia, neutropenia, and myeloneuropathy; excess occurs in Wilson disease. Functional testing complements serum copper and ceruloplasmin in malabsorption, Wilson disease screening, and suspected subclinical imbalance where serum measures are discordant.

Selenium is incorporated into selenoproteins, including glutathione peroxidases and thioredoxin reductases, which are central to antioxidant defence and thyroid hormone metabolism. Cellular assays measure functional selenoprotein activity when selenium is rate-limiting.

Selenium insufficiency impairs immune function, thyroid hormone metabolism, and antioxidant capacity, and is associated with cardiomyopathy (Keshan disease) and increased viral mutation rates. Functional testing is used in low-selenium regions, parenteral nutrition, malabsorption, and critical illness.

Chromium potentiates insulin signalling, though the precise molecular mechanisms and status assessment remain debated. Cellular assays measure lymphocyte functional response when chromium is limiting, used as a proxy for tissue status.

Chromium insufficiency has been linked to impaired glucose tolerance and insulin resistance in some but not all studies. Functional testing is used in refractory dysglycaemia and parenteral nutrition, though clinical chromium deficiency is rare and contested.

Coenzyme Q10 (ubiquinone) is a lipid-soluble component of the mitochondrial electron transport chain and a membrane antioxidant. Functional assays measure lymphocyte bioenergetic capacity when CoQ10 is rate-limiting.

CoQ10 insufficiency is seen in primary mitochondrial disorders, statin therapy, and ageing. It is associated with myopathy, cardiomyopathy, and fatigue. Functional testing is used in suspected mitochondrial dysfunction, statin-related myalgia, and heart failure where serum CoQ10 may not reflect tissue status.

Alpha-lipoic acid is a cofactor for mitochondrial dehydrogenase complexes and a potent antioxidant that recycles other antioxidants (vitamins C and E, glutathione). Cellular assays measure functional capacity when alpha-lipoic acid is rate-limiting.

Alpha-lipoic acid is used therapeutically in diabetic neuropathy and oxidative stress disorders. Functional testing is exploratory, used in mitochondrial support protocols and refractory neuropathy, though deficiency states are not well defined.

Inositol is a component of phosphatidylinositol signalling pathways and membrane structure. Cellular assays assess functional inositol availability in lymphocyte signalling.

Inositol insufficiency is implicated in insulin resistance, polycystic ovary syndrome, and mood disorders, though the evidence base is still evolving. Functional testing is used in integrative and functional medicine protocols.

Choline is a precursor of acetylcholine, phosphatidylcholine, and betaine, linking neurotransmission, membrane synthesis, and one-carbon metabolism. Cellular assays measure functional choline availability when it is rate-limiting.

Choline insufficiency can cause fatty liver and muscle damage and may impair methylation and neurotransmitter synthesis. Functional testing is used in non-alcoholic fatty liver disease, pregnancy, and settings where choline demand is high, though plasma choline and metabolites are the more established markers.

Glutathione is the principal intracellular antioxidant and a cofactor for glutathione peroxidases and transferases, central to redox homeostasis, detoxification, and immune function. Cellular assays measure functional glutathione-dependent antioxidant capacity in lymphocytes.

Glutathione depletion is associated with oxidative stress, immune dysfunction, and impaired detoxification in chronic illness, toxin exposure, and genetic polymorphisms in glutathione synthesis or recycling. Functional testing is used in chronic fatigue, environmental illness, and neuroinflammatory conditions where oxidative stress is suspected.