An essential B vitamin required for DNA synthesis, red blood cell formation, neural tube development, and homocysteine regulation.
What it is
Vitamin B9 is an essential water-soluble B vitamin encompassing synthetic folic acid (pteroylmonoglutamic acid) and naturally occurring folates (such as 5-methyltetrahydrofolate or 5-MTHF). In dietary supplements, L-methylfolate or folic acid is utilized to ensure high chemical stability and bioequivalence. Vitamin B9 serves as an essential carrier of one-carbon units in nucleic acid synthesis, amino acid metabolism, and cellular methylation reactions.
Also known as: Folate, L-Methylfolate, Methylfolate, 5-MTHF
What it does
- Drives cell division and DNA replication during fetal growth and tissue regeneration.
- Supports healthy red blood cell production, preventing megaloblastic anemia.
- Converts homocysteine to methionine, maintaining cardiovascular and cerebrovascular health.
- Reduces the risk of neural tube defects during early pregnancy.
Amplified by probiotics
Human enterocytes absorb dietary folate via proton-coupled folate transporters (PCFT) operating within an acidic microenvironment. Specific probiotic strains—notably Bifidobacterium adolescentis, Bifidobacterium pseudocatenulatum, and Lactobacillus plantarum—possess full enzymatic pathways to synthesize active folate forms (including 5-methyltetrahydrofolate or 5-MTHF) de novo within the gut lumen. Supercritical-CO2 microencapsulation protects live strains through stomach acid, ensuring high-density delivery to the intestine. As these probiotics colonize, their fermentation produces short-chain fatty acids (SCFAs) that lower luminal pH, directly enhancing PCFT uptake kinetics across the intestinal mucosa. This continuous microbial synthesis maintains localized epithelial folate pools, preventing oxidative DNA strand breaks in enterocytes and supporting rapid mucosal tissue renewal.
Typical dose
400–800 µg/day
The evidence
Evidence: strongExtensive global clinical research establishes that periconceptional folic acid supplementation prevents neural tube defects, lowers plasma homocysteine, and supports erythropoiesis. Systematic reviews confirm the bioequivalence and superior absorption of L-methylfolate (Crider et al. 2012, Am J Clin Nutr; Scaglione & Panzavolta 2014, Xenobiotica).
- Crider KS, et al. Folate and DNA methylation: a review of molecular mechanisms and the evidence for folate's role. Am J Clin Nutr. 2012;95(1):261S-272S. PubMed ↗
- Scaglione F, Panzavolta G. Folate, folic acid and 5-methyltetrahydrofolate options for nutrient deficiency. Xenobiotica. 2014;44(5):480-488. PubMed ↗
Safety & who should check first
Tolerable Upper Intake Limit is 1,000 µg/day for synthetic folic acid to prevent masking B12 deficiency. Essential in pregnancy; methylfolate carries no risk of unmetabolized folic acid accumulation.