Vitamin B9

Physiological Role

Folate, or vitamin B9, is a water-soluble vitamin that the body cannot synthesize. It must be obtained through diet: green leafy vegetables, legumes, liver, and citrus fruits. Once absorbed, folate is converted into 5-methyltetrahydrofolate (5-MTHF), its biologically active form. This conversion requires the enzyme MTHFR (methylenetetrahydrofolate reductase), whose activity varies with genetic profile.

5-MTHF plays a key role in the methylation cycle. It provides a methyl group to homocysteine to reconvert it into methionine, an essential amino acid. This transfer requires vitamin B12 as a cofactor. Methionine is then transformed into S-adenosylmethionine (SAM), the body's primary methyl donor. SAM is involved in gene regulation, neurotransmitter synthesis, and DNA integrity maintenance.

Red blood cell folate measurement assesses the concentration of folate stored in red blood cells. Serum folate fluctuates with recent dietary intake. Red blood cell folate reflects vitamin B9 status over two to four months. It provides a more stable indicator of tissue reserves.

Reference Ranges

These reference ranges are derived from scientific literature and may differ from your laboratory's reference values.

Source : WHO, Serum and red blood cell folate concentrations for assessing folate status in populations (2015)

Biological Significance

Red blood cell folate provides a reliable reading of vitamin B9 status over the medium term. Values within the optimal range indicate sufficient tissue reserves to support the methylation cycle and normal cell division.

Low values may reflect insufficient dietary intake over several weeks, reduced intestinal absorption, or increased requirements linked to a genetic polymorphism. A sustainably low folate status is associated with elevated homocysteine, a marker of methylation cycle function that Singular measures concurrently.

High values generally reflect supplementation or a folate-rich diet. Folate is a water-soluble vitamin: excess is eliminated through renal excretion. Regular monitoring helps distinguish a one-time variation from a lasting trend and adapt the nutritional protocol accordingly.

Red blood cell folate is read in conjunction with vitamin B12 and homocysteine. These three markers, measured together, provide a map of the methylation cycle. Mean corpuscular volume (MCV) provides complementary information: an elevated MCV may signal increased folate or vitamin B12 requirements.

Influencing Factors

Diet. Green leafy vegetables (spinach, broccoli, asparagus), legumes, liver, and citrus fruits are the richest dietary sources of natural folates. Prolonged cooking significantly reduces folate content in food.

Genetics. The MTHFR C677T polymorphism affects approximately 10% of the European population in homozygous form. It reduces the folate-to-active-form conversion enzyme activity by 50 to 70%. Carriers have increased methylfolate requirements.

Intestinal absorption. Dietary folates are absorbed primarily in the proximal jejunum (upper part of the small intestine). A compromised intestinal mucosa may reduce this absorption. Alcohol consumption also interferes with intestinal folate transport.

Alcohol. Regular alcohol consumption decreases intestinal folate absorption and accelerates urinary excretion. This effect is dose-dependent and represents one of the most common factors behind low folate status.

Medications. Certain medications can interfere with folate metabolism, notably methotrexate, some anticonvulsants, and oral contraceptives. It is useful to report any ongoing medication when interpreting results.

Age and increased requirements. Folate requirements increase during pregnancy and breastfeeding. With age, intestinal absorption may decrease. Older adults more frequently present low red blood cell folate values.

Supplementation. 5-methyltetrahydrofolate (5-MTHF), the active form of folate, is directly usable by the body. It is preferred over synthetic folic acid, which requires enzymatic conversion varying with genetic profile.

In the Singular Formula

Vitamin B9 is one of the markers most directly integrated into the Singular personalization engine. Red blood cell folate serves as both a nutritional adjustment parameter and a methylation cycle monitoring signal.

In a very low range, the vitamin B9 dosage as 5-MTHF (calcium L-5-methyltetrahydrofolate) reaches its highest level. It supports normal blood formation. A low range triggers an intermediate dosage. A satisfactory status in the lower optimal range maintains a maintenance dose.

The formulation engine also accounts for homocysteine. When homocysteine is elevated and folate is low with optimal vitamin B12, the 5-MTHF dosage is reinforced. It supports normal homocysteine metabolism. If both vitamins are optimal but homocysteine remains elevated, the formula combines vitamin B9 and vitamin B12 (methylcobalamin) at moderate doses.

Trimethylglycine (TMG) and vitamin B6 (P5P) complement this system. Trimethylglycine is a methyl group donor supporting homocysteine-to-methionine conversion. Vitamin B6 is involved in the transsulfuration pathway, the other homocysteine recycling route. Singular concurrently measures red blood cell folate, vitamin B12, and homocysteine.

Scientific Studies

Frequently Asked Questions