INTRODUCTION:

Folate is an essential water-soluble vitamin occurring naturally in select foods as well as in the synthetic form (folic acid) used in supplements and in food fortification programs¹. One vital vitamin, folic acid (FA), is involved in several vital biological functions, such as DNA synthesis, repair, and methylation. When homocysteine is converted to methionine, its active form 5-methyltetrahydrofolate (5-MTHF) acts as a methyl donor. Methionine is then further broken down to S-adenosylmethionine (SAM), the universal methyl donor for DNA and histone methylation1. Because folate is essential for epigenetic regulation, its availability can have a significant impact on patterns of gene expression, especially in the early stages of development when epigenetic marks are formed². Early embryogenesis is a critical time for the establishment of precise DNA methylation patterns that impact cell differentiation and long-term health outcomes, making folate's role in epigenetic programming especially important³. Beyond development, the nutrient's wide-ranging effects on health have been highlighted by the association of folate-mediated epigenetic changes with ageing, cancer, cardiovascular disease, and neurological disorders⁴. On the other hand, consuming too much folate, especially synthetic folic acid, has sparked worries about possible unforeseen repercussions such changed methylation patterns that could affect the course of cancer⁵.

Figure 1. Folic acid metabolism. Crider, K. S., et al.¹

This schematic shows the process by which folate/folic acid is used for DNA methylation. In addition to decreasing enzyme activity, the MTHFR 677C→T variation may aid in rerouting available methyl groups from the DNA methylation pathway. The pathway is intricate and well controlled. includes interactions and feedback loops not depicted in the diagram. Cofactors are included in parenthesis, and enzyme gene names are italicised. Methionine synthase (MS), methylenetetrahydrofolate reductase (MTHFR), dihydrofolate reductase (DHFR), thymidylate (dTMP), deoxyuridine monophosphate (dUMP), SAH (S-adenosylhomocysteine), SAM (S-adenosylmethionine), serine hydroxymethyltransferase (SHMT), tetrahydrofolate (THF), and thymidylate synthase (TS).

The idea that a lack of folate would make epithelial cells more likely to undergo a neoplastic transformation seems a little counterintuitive at first. Folate plays a crucial role in several cell metabolic processes that entail the transfer of one-carbon groups⁶.

This review explores and analyses the clinical and public health implications of optimising folate consumption for disease prevention, looks at the effects of folate deficiency and supplementation on gene expression, and explores the molecular routes connecting folate metabolism to epigenetic control. We hope to offer a thorough grasp of how this vital nutrient influences the epigenome from early development through maturity by combining data from molecular, epidemiological, and translational research.

Folate Metabolism and Epigenetic Regulation:

Folate's pivotal role in one-carbon metabolism, a web of metabolic processes that produce methyl groups necessary for DNA and histone modifications, accounts for its function as a crucial mediator between nutrition and epigenetic control. The metabolic pathways that connect folate to epigenetic changes and their physiological implications are examined in this section.

· One-Carbon Metabolism and Methyl Group Provision: A vital part of one-carbon metabolism, the folate cycle interacts with the methionine cycle to control the methylation capacity of cells⁷. The methionine cycle, methylation reactions, and folate activation are important processes. S-adenosylhomocysteine (SAH), the byproduct of demethylation, is a strong methyltransferase inhibitor, establishing a feedback loop in which methylation ability is directly influenced by folate status⁸.

· DNA Methylation Dynamics: Through a number of mechanisms, the availability of folate has a significant impact on DNA methylation patterns. This covers transgenerational inheritance, gene-specific effects, and global DNA methylation^9,10.

· Histone Modification Networks: Folate affects gene expression by histone modifications in addition to DNA methylation. Bivalent chromatin domains in stem cells are altered by folate deprivation¹¹. Polymorphisms, interactions between micronutrients, and environmental exposures such as alcohol and xenobiotics that interfere with folate metabolism alter the epigenetic impact of folate¹².

Developmental Programming and foetal Epigenetics:

Folic acid's capacity to influence the fatal epigenome during times of dynamic epigenetic remodelling accounts for its crucial function in embryonic programming. According to epidemiological research, methylation levels at imprinted genes like IGF2 are closely correlated with maternal folate status; for every 10% increase in maternal red blood cell folate, there is a corresponding 0.3% increase in methylation at the IGF2 differentially methylated region¹³. Human studies have demonstrated that newborns from mums who are folate-sufficient have 5–15% more LINE-1 methylation than those from mothers who are deficient, demonstrating that these epigenetic changes impact global methylation patterns in addition to imprinted genes⁵. There are several interrelated ways that folate affects developmental programming. First, folate supplies methyl groups that are necessary for the development of methylation patterns specific to cell types throughout embryogenesis, especially during the postfertilization wave of epigenetic reprogramming¹⁴. Second, folate influences histone modification landscapes in developing tissues, with deficiency leading to reduced H3K27 me3 at neurodevelopmental loci such as Pax6 and decreased H3K4me3 at metabolic regulators like Ppargc1a¹⁵. Third, folate creates feedback loops that enhance its developmental effects by modifying the expression of epigenetic regulators themselves, such as Tet enzymes and DNMTs1. Natural population variances or responses to outside stimuli can cause epigenetic alterations, which alter how genes are expressed. The neonate will be impacted by epigenetic modifications in the mother's DNA if they are inherited¹⁶. The correlation between maternal folate deficit and altered methylation at genes governing neural tube closure and heart development demonstrates how these processes interact to impact organogenesis¹⁷. A revolutionary idea in neurodevelopmental biology is the transgenerational epigenetic inheritance of folate mediated effects, which shows how maternal folate status can affect brain development across several generations by causing long-lasting epigenetic changes¹⁸. There is strong evidence from animal models that folate deficit in F0 mum’s changes DNA methylation patterns in F1 children as well as F2 and F3 generations, especially at genes controlling neurogenesis and synaptic plasticity. These effects show up as behavioural traits; in Morris's water maze paradigms, F3 offspring of folate-deficient grandparents exhibit worse spatial recall and 2.3 times more anxiety-like responses in open field assessments¹⁹.

Folate and Disease: From Cancer to Neurological Disorders:

Folate is a crucial regulator of illness risk across the lifetime because of its dual function in preserving genomic stability and controlling epigenetic programming. Folate has two effects in cancer biology: whereas a sufficient level of folate prevents DNA damage and uracil misincorporation, which prevents the development of tumours²⁰, through aberrant DNA hypermethylation, high folic acid supplementation may accelerate the development of preneoplastic lesions that have already been developed. Folate insufficiency raises the risk of colon cancer, according to epidemiological research, especially in people with the MTHFR 677TT genotype²¹. The absence of correlation between colonic biopsy specimens and erythrocyte folate levels in healthy persons was reported by Meenan et al.²², suggesting that localised folate insufficiency may be difficult to anticipate. In a later research²³, folate depletion of epithelial cells was observed in cancer cells but not in the nearby normal colonic mucosa. On the other hand, there was a strong correlation between the folate content of colon biopsy samples and the levels of red cell and blood folate in patients with polyps²⁴. A study in a genetically modified mouse model of a human cancer has demonstrated that folic acid deficiency during the peri-gestational period protects or reduces the formation of medulloblastoma. Research in rodent models has demonstrated that supplementing with FA accelerates the progression of mammary tumours^25,26.

Molecular mechanisms of folic acid's possible carcinogenic effects: Folate is a likely growth factor for neoplastic cells²⁷ due to its functions in nucleotide synthesis and as a cofactor in the rate-limiting phase of DNA synthesis²⁸. Certain vitamins are used at high rates by cells that divide aggressively, including those found in solid tumours. The receptors that are in charge of absorbing certain vitamins are therefore overexpressed²⁹. Furthermore, the expression of some essential folate-dependent enzymes required for DNA synthesis and membrane receptors mediating folate uptake can be upregulated by a large number of cancer cells^30,31. Malignant tissues of both epithelial and non-epithelial origin express two folate receptors, folate receptor α and FR-β. Additionally, they have been found in tumours of myeloid hematopoietic cells, the brain (66%), placental cells, lung cancer (50%), endometrial cancer, renal cancer (50%), colorectal cancer (CRC), and ovarian carcinoma. The tumour stage has also been closely linked to the levels of FR expression in tumours²⁹.

Through both epigenetic and non-epigenetic routes, folate's impact on one-carbon metabolism has a direct impact on brain function in neurological diseases. Due mainly to altered methylation of neurodevelopmental genes, severe folate shortage during early development might raise the chance of neural tube abnormalities by up to ten times¹⁵. Low serum folate levels are linked to a 2.5-fold increased risk of Alzheimer's disease, indicating that folate deficiency leads to dementia and cognitive decline later in life³². Folate plays a part in mediating these effects by controlling the methylation-dependent expression of genes involved in neurotransmitter production and synaptic plasticity³³. There is also growing evidence that psychiatric disorders are linked to folate metabolism. Low folate levels are common in depression patients, and supplementing with folate (especially L-methyl folate) can increase the effectiveness of antidepressant drugs by up to 25% in instances that are resistant to treatment³⁴. In a similar vein, folate deficiency worsens negative symptoms in schizophrenia, but supplementation improves outcomes, particularly for those who carry the FOLH1 rs202676 variation³⁵. These results highlight the crucial relationship that exists throughout the lifespan between brain function, epigenetic control, and folate metabolism.

Clinical and Public Health Perspectives:

Both opportunities and obstacles arise when folate-epigenetics research is translated into clinical practice and public health policy; dose, timing, and population-specific aspects must be carefully considered. Since the 1990s, folic acid fortification programmes have been in place in more than 80 nations, and they have decreased the prevalence of neural tube defects in a variety of populations by 28–55%³⁶. The technique of adding vital micronutrients that are deficient in a population's diet to regularly consumed foods while they are being processed is known as food fortification³⁷. This procedure was a turning point that can lessen shortages in micronutrients in a variety of ways³⁸. Without a doubt, these deficits can impact a person's ability to survive as well as their mental and physical growth, which can then have an impact on a nation's economy^39,40. With early clinical trials showing that MTHFR 677TT carriers receiving L-methyl folate (the bioactive form) exhibit 35% greater improvements in endothelial function and cognitive scores compared to those receiving synthetic folic acid, precision nutrition approaches now support genotype-tailored supplementation⁴¹. The FDA authorised the combination of ferrous ascorbate and folic acid in 2011. Both of these medications are essential vitamins that support expectant mothers in maintaining their health throughout their pregnancy⁴². Research has discovered that folate-conjugated nanoparticles containing medications such as paclitaxel or doxorubicin are far more cytotoxic to MCF-7 and MDA-MB-231 breast cancer cells. This is explained by the fact that these cells effectively internalise them through endocytosis mediated by the folate receptor⁴³. In addition to neural tube abnormalities, FA may be useful as a supplement during pregnancy to avoid other pregnancy-related complications⁴⁴.

Studies on the relationship between dietary folate consumption and carcinoma show that people with the highest dietary folate intake had an average 35% lower risk of colon cancer than those with the lowest intake^45,46. Another important factor to take into account is the timing of folate therapies. According to epigenetic clock analysis, periconceptional supplementation results in more significant and long-lasting changes in DNA methylation than postnatal interventions⁴⁷. Our knowledge of the epigenetic effects of folate has been completely transformed by recent developments in multi-omics technologies, which allow for high-resolution mapping of the intricate interactions between gene expression, chromatin dynamics, DNA methylation, and folate metabolism. Folate deficiency causes locus-specific hypomethylation (15–30% reduction) at enhancer regions, especially those regulating neural development and one-carbon metabolism genes, according to integrative analyses combining whole-genome bisulphite sequencing, ATAC, and RNA-sequence in folate-deficient models⁴⁸. With an accuracy of >89%, newly developed machine learning models that use multi-omics data can now predict folate-responsive epigenetic regions, potentially opening up therapeutic applications for customised folate supplementation plans⁴⁹. Furthermore, after fortification started, NTDs have decreased in Canada, South Africa, Costa Rica, Chile, Argentina, and Brazil (19% to 55%)^50,51. Fortification with folic acid has also been shown to offer some unexpected advantages. These include higher haemoglobin levels and a decreased risk of CVD, primarily due to a decrease in total homocysteine (tHcy), a risk factor for CVD in and of itself⁵². Enhanced cognitive function is also an observed benefit⁵³. The protective effects of folic acid may vary depending on the type of cancer. Figure 2 summarizes the currently known molecular mechanisms of the folic acid-mediated protective effects against cancer.

Figure: 2 Molecular mechanisms of the protective effect of folic acid against cancer. Thabet RH et al.⁵⁴

These mechanisms include its role in nucleotide synthesis, DNA methylation, homocysteine metabolism, DNA repair, and reduction of oxidative stress. ALDH1, Aldehyde Dehydrogenase 1; CYP2E1, Cytochrome P450 2E1⁵⁴.

Role of folic acid in homocysteine regulation:

Folate is involved in converting homocysteine into methionine⁵⁵. Elevated homocysteine levels are associated with a higher risk of various diseases, including certain cancers^56,57. In diabetes patients, plasma homocysteine levels can be elevated in insulin-resistant states (lowered by insulin)⁵⁸. Therefore, adequate folate intake can help reduce homocysteine levels, potentially lowering the risk of pancreatic cancer⁵⁹. These multimodal strategies will be crucial for optimising benefits and reducing potential hazards across a range of populations and generations as research continues to clarify the complex relationships between folate, epigenetics, and illness.

CONCLUSION:

From developmental biology to disease prevention to transgenerational inheritance, folic acid's function as a basic mediator between nutrition and the epigenome has broad implications for human health. This review emphasises how folate plays a crucial role in regulating gene expression by orchestrating DNA methylation, histone changes, and chromatin remodelling through its important role in one-carbon metabolism. A more sophisticated approach to supplementation and fortification regulations is required due to the dose-dependent, timing-specific, and genetic background-influenced epigenetic effects of folate. Despite the fact that folate shortage is unquestionably associated with negative consequences, such as neural tube malformations, cognitive decline, and an increased risk of cancer, new research warns against consuming too much of it since this could alter natural epigenetic patterns and encourage cancer in individuals who are at risk. To sum up, folic acid is a prime example of how a single vitamin may have significant and widespread impacts on the epigenome, influencing health outcomes from infancy to old age. Folate continues to be a model for comprehending how food affects genomic regulation as we work to understand the complexity of nutrient-epigenome interactions-a real bridge "from nutrient to nucleus."

SUMMARY OF KEY FINDINGS:

Significant findings highlight how even minute changes in folate levels, whether in excess or in deficit, can cause long-lasting epigenetic modifications, especially during delicate stages like embryogenesis and the early stages of foetal development. Folate has the ability to influence gene expression and health throughout generations, making it more than just a vitamin. The fundamental reality that we are not just what we eat, but also what our predecessors ate and what we carry on to future generations, is highlighted by its story.

LIST OF ABBREVIATIONS:

FA: Folic Acid

MTHF: Methyltetrahydrofolate

SAM: S-Adenosylmethionine

THF: Tetrahydrofolate

DHFR: Dihydrofolate reductase

DUMP: Deoxyuridine Monophosphate;

DNMTs: DNA methyltransferases

FR: Folate Receptor

CRC: Colorectal Cancer

AVAILABILITY OF DATA AND MATERIALS:

All data and materials are available upon request.

COMPETING INTERESTS:

The authors declare that they have no competing interest.

AUTHORS CONTRIBUTIONS:

All authors have reviewed and approved the final manuscript. Dhruva Hegde contributed to the conceptualization and writing of the review. Pinki Verma was responsible for drafting and making significant revisions to the manuscript and provided guidance, and conducted thorough proofreading to ensure the quality of the work.

ACKNOWLEDGEMENT:

I would like to express my sincere gratitude to Dr. B.A. Vishwanath, Chairman, Aditya Group of Institutions, Bangalore, for his invaluable guidance, support, and encouragement throughout the preparation of this review.

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Received on 16.07.2025 Revised on 08.10.2025

Accepted on 24.12.2025 Published on 06.07.2026

Available online from July 20, 2026

Asian J. Pharm. Res. 2026; 16(3):306-312.

DOI: 10.52711/2231-5691.2026.00045

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