Testing B Vitamin Status

B vitamins are a group of water-soluble micronutrients. They are vital to cell function and act as coenzymes in several metabolic activities, including energy generation, methylation, red and white blood cell development, antioxidant activity, DNA metabolism and repair, cell signaling, and the processing of carbohydrates, protein, and fat (Kennedy 2016).

B vitamin status can be evaluated clinically using laboratory assessment along with a nutrition-based physical assessment to identify signs of deficiency.

        
The role of B-vitamins in mitochondrial energy production

Source: Kennedy, David O. “B Vitamins and the Brain: Mechanisms, Dose and Efficacy--A Review.” Nutrients vol. 8,2 68. 27 Jan. 2016, doi:10.3390/nu8020068 This article is an open access article distributed under the terms and conditions of the Creative Commons by Attribution (CC-BY) license (http://creativecommons.org/licenses/by/4.0/).

Functional B Vitamin Testing

Direct measurement of B vitamins in the blood or in red blood cells provides information about the amount immediately available to cells. However, testing of compounds that utilize or affect B vitamins provides more information about the metabolism and cellular utilization of B vitamins.

Alanine aminotransferase (ALT)

• Low levels of ALT may be associated with an insufficiency of vitamin B6 (Ramati 2015).
• Alanine aminotransferase (ALT), previously known as SGPT, is an enzyme that participates in gluconeogenesis. It facilitates the transfer of amino groups from alanine to alpha-ketoglutarate to produce glutamate as well as pyruvate, which can then be converted to energy via the Krebs cycle, a vitamin B6-dependent process (Moriles 2021).

Alkaline phosphatase (ALP)

• Low ALP may also be seen with B12 deficiency, cardiac surgery, cardiopulmonary bypass, and zinc and magnesium insufficiency (Ray 2017)
• Excess B vitamin intake may reduce ALP (Pagana 2022).
• Alkaline phosphatase enzymes participate in phosphorylation, bone metabolism, cell growth, and apoptosis (Sharma 2014).

Aspartate aminotransferase (AST)

• Low serum AST can be related to vitamin B6 insufficiency, which in turn is associated with increased cardiovascular risk (Ndrepepa 2021).
• Low levels of AST may be seen with severe chronic liver disease, uremia, acute kidney disease, chronic hemodialysis, diabetic ketoacidosis, and pregnancy (Pagana 2022).
• Aspartate aminotransferase, previously known as SGOT, participates in gluconeogenesis, the conversion of amino acids into glucose.

Anion Gap

An increased anion gap may be associated with an insufficiency of thiamine, which can lead to a buildup of lactic acid (Hammond 2013, O’Donnell 2017).

It is important to evaluate the risk of thiamine deficiency, including intake of excess carbohydrates and insufficient thiamine intake. Since thiamine plays such an important role in glucose metabolism, an increase in dietary carbohydrates increases the relative need for thiamine (Dhir 2019).

Diamine Oxidase (DAO)

A low-histamine diet can provide relief from histamine intolerance symptoms and may even increase serum levels of DAO. Consuming adequate cofactors for DAO production may also improve HIT symptoms, these include vitamin B6, vitamin C, and copper (Hrubisko 2021).

Gamma-glutamyl transferase (GGT)

Low GGT levels may be associated with vitamin B6 insufficiency (Thomas 1998).

Holotranscobalamin

Approximately 20-25% of circulating B12 (cobalamin) is bound to transcobalamin in a complex called holotranscobalamin (holoTC). The holoTC is biologically active and readily taken up by the cell. It is considered the most direct measurement of vitamin B12 status (Nexo 2011).

Homocysteine

The most common cause of elevated homocysteine is insufficient vitamins B6, B12, or folate (Pagana 2022). However, riboflavin is also important to maintaining healthy homocysteine levels (Elias 2022, Hanna 2022). Elevated homocysteine is also associated with elevated red cell distribution width (Peng 2017).

Methylmalonic acid (MMA)

Methylmalonic acid (MMA) is considered an early indicator of B12 insufficiency but also serves as a biomarker of mitochondrial dysfunction and oxidative stress (Polytarchou 2020).

MMA is formed when a lack of vitamin B12 leads to the impairment of methylmalonyl-CoA mutase, the enzyme that converts methylmalonyl-CoA to succinyl-CoA in the citric acid/tricarboxylic acid cycle (Harrington 2017).

Methylmalonyl-CoA is a byproduct of the metabolism of propionic acid, which is produced by the breakdown of branch-chain amino acids, odd-chain fatty acids, and cholesterol sidechains and by bacterial fermentation in the colon. Accumulating methylmalonyl-CoA and intermediary propionyl-CoA is toxic to the cell and contributes to impaired gluconeogenesis, fatty acid oxidation, pyruvate oxidation, and ureagenesis (Riphagen 2020).

Mean Corpuscular Volume (MCV)

A decreased MCV can be associated with B6 insufficiency (Maner 2021), while an elevated MCV can be associated with megaloblastic anemia and B12 or folate insufficiency (Pagana 2022).

Mean Platelet Volume (MPV)

The MPV can be increased with a B12 or folate deficiency (Pagana 2022).

Red Cell Distribution Width (RDW)

An increase in RDW is seen with folate and B12 deficiencies (Fava 2019).

Reticulocytes

Reticulocytes are also low in the presence of certain anemias, including aplastic anemia, megaloblastic anemia (e.g., pernicious anemia, vitamin B12 and/or folate deficiency); hypochromic anemias (e.g., iron deficiency, sideroblastic, and anemia of chronic disease) (Pagana 2022, Riley 2001),

Unsaturated Iron Binding Capacity (UIBC)

A vitamin B12/cobalamin deficiency can mask iron deficiency and interfere with the accurate assessment of UIBC. In a study of 75 patients with cobalamin deficiency, serum iron, ferritin, and transferrin saturation levels were increased while UIBC was decreased, suggesting iron sufficiency. After cobalamin therapy, serum iron, ferritin, and transferrin saturation decreased significantly while the UIBC increased significantly, revealing a likely iron insufficiency (Solmaz 2015).

Additional Notes

Cobalamin (B12)

B12 works with other B vitamins and supports several physiological activities, including mitochondrial energy generation, protein metabolism, DNA synthesis, red blood cell production, folate metabolism, and the conversion of homocysteine to methionine. Insufficiency of B12 will disrupt these functions and contribute to anemia, fatigue, neuropathy, cognitive impairment (especially with the ApoE4 genotype), and reproductive impairment (Allen 2018).

Vitamin B12 also appears to function as an antioxidant. It may help scavenge superoxide, preserve glutathione, protect against the oxidative stress associated with homocysteine and advanced glycosylation end products, and modulate the oxidation and inflammation associated with the immune response (van de Lagemaat 2019). Oxidative stress and glutathione insufficiency, in turn, contribute to intracellular functional B12 deficiency (Vollbracht 2020).

A B12 deficiency can lead to cellular accumulation of 5-MTHF (the “methyl-folate trap”) as well as homocysteine despite adequate folate availability (Ohrvik 2011).

Folate, RBC Folate

The adverse effects of unmetabolized folic acid may be magnified with compromised vitamin B12 status, resulting in elevated homocysteine and methylmalonic acid and decreased holotranscobalamin (active B12). A combination of elevated folate and insufficient B12 in mothers may contribute to the incidence of insulin resistance and stunted growth in their offspring. Vitamin B12 status should be evaluated along with folate, especially if folate levels in the blood are elevated, which may reflect insufficient B12. The combination of folate and B12 deficiency is associated with neuropathy, cognitive decline, and depression (Sobczyńska-Malefora 2018).

RBC folate, serum folate, and homocysteine levels should be part of a comprehensive assessment of folate status (Ohrvik 2011). Folate interacts closely with vitamins B2 and B6 as well, and these vitamins should be assessed along with folate (Bailey 2015).

Folate supplementation should always be combined with vitamin B12 to avoid masking a B12 deficiency (Pizzorno 2016).

Niacin (B3)

Niacin can be produced in the body from the amino acid tryptophan, a process that requires riboflavin, another example of the interdependent nature of B vitamins (Hanna 2022).

Pyridoxine (B6)

A comprehensive evaluation is needed to assess B6 status in order to overcome potential confounding variables that can affect levels, including inflammation, alcohol intake, renal function, low albumin (albumin transports PLP), inorganic phosphate (elevations of which increase plasma PLP), and alkaline phosphatase activity.

Research suggests an inverse association between PLP and acute-phase reactants, CRP, and other inflammatory markers (Ueland 2015).

Thiamine (B1)

Thiamine is essential to energy generation, amino acid metabolism, synthesis of nucleic acids, antioxidant systems, cell membrane stability, myelin sheath maintenance, nerve conduction, and synthesis of glutamate and gamma-aminobutyric acid (GABA) (Hammond 2013).

Thiamine deficiency and insufficiency of active thiamine pyrophosphate can lead to increased glutamate and decreased production of acetylcholine and myelin, leading to delirium (Hanna 2022).

Research suggests that thiamine deficiency may be also be associated with vascular inflammation, myocardial infarction, heart failure, diabetes, obesity, conduction deficits, and depression (Eshak 2018).

Interlinked folate and methionine cycles

Source: Kennedy, David O. “B Vitamins and the Brain: Mechanisms, Dose and Efficacy--A Review.” Nutrients vol. 8,2 68. 27 Jan. 2016, doi:10.3390/nu8020068 This article is an open access article distributed under the terms and conditions of the Creative Commons by Attribution (CC-BY) license (http://creativecommons.org/licenses/by/4.0/).

Source: Kennedy, David O. “B Vitamins and the Brain: Mechanisms, Dose and Efficacy--A Review.” Nutrients vol. 8,2 68. 27 Jan. 2016, doi:10.3390/nu8020068 This article is an open access article distributed under the terms and conditions of the Creative Commons by Attribution (CC-BY) license (http://creativecommons.org/licenses/by/4.0/).

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