HSA | FSA CARDS ARE NOW ACCEPTED

Last reviewed: May 12, 2026 Last updated: May 12, 2026

Written by: Jay Hastings , CEO of PlexusDx

Jay Hastings is the CEO of PlexusDx, a precision health company focused on genetic testing, blood biomarker insights, and personalized wellness recommendations. He has more than 20 years of experience across healthcare innovation, genomics, laboratory operations, healthcare investing, and strategic finance. His work has included scaling healthcare startups, leading CLIA lab integrations, and helping expand consumer access to precision health tools.

Medically reviewed by: Jayden Lee, PharmD, EMBA

Jayden Lee, PharmD, EMBA, is the PlexusDx Medical Science Liaison with a PharmD and MBA specializing in pharmacogenomics and clinical product development, with a proven ability to bridge the gap between genomic research and practical patient outcomes. Dr. Lee has more than 10 years of professional experience in clinical pharmacy, academia, and research.

SHMT1 and One Carbon Metabolism: What Your Genotype Means

The SHMT1 gene encodes serine hydroxymethyltransferase 1, an enzyme that plays a central role in folate dependent one carbon metabolism. SHMT1 converts serine and tetrahydrofolate into glycine and 5,10-methylenetetrahydrofolate. These products support DNA synthesis, nucleotide balance, and the supply of methyl groups for the Methionine Cycle and methylation reactions. Proper SHMT1 function helps maintain healthy gene regulation, detoxification, and homocysteine balance. Variations in SHMT1 can subtly shift how folate is used by the body and influence nutritional needs under stress, high DNA synthesis demand, or low dietary folate.

Why SHMT1 Genotype Matters

  • SHMT1 directs folate toward either DNA synthesis or methylation. Small changes in enzyme function can change availability of folate intermediates.
  • Impaired folate flow can influence thymidylate synthesis, methylation capacity, and homocysteine clearance.
  • Genetic differences often interact with diet and lifestyle. Genotype is one factor among many that determine individual nutrient needs.

Genetic Interpretations

2 effect alleles (AA) — what this can mean

The AA genotype at rs1979277 results in an amino acid substitution in SHMT1. Literature reports are mixed. Reduced SHMT1 activity has more often been tied to the CC genotype in some studies, and AA has not been consistently associated with reduced enzyme function. Some evidence links AA with altered thymidylate synthase activity, which can change DNA synthesis demands.

Practical implications: AA is not typically linked to clear impairment in folate metabolism, but maintaining good folate status and supporting cofactors helps ensure robust methylation and nucleotide balance, especially during times of increased demand.

1 effect allele (AG) — what this can mean

The AG genotype indicates one copy of the effect allele. In most people this results in near normal SHMT1 enzyme activity. The heterozygous state may allow subtle shifts in levels of folate intermediates under conditions of low dietary folate, high cell division, or increased methylation demand.

Practical implications: With one effect allele, most people will do well with a balanced intake of folate and methylation cofactors. Pay attention to diet and nutrient status if you have additional genetic variants or health conditions that affect one carbon metabolism.

0 effect alleles (GG) — what this can mean

The GG genotype is associated with typical SHMT1 enzyme function. With normal activity, the Folate Cycle and Methionine Cycle are more likely to be well supported, provided dietary intake of folate and B vitamins is sufficient.

Practical implications: Standard dietary recommendations for folate and B vitamins usually support healthy methylation and nucleotide synthesis in people with this genotype.

Diet Recommendations

  • Prioritize natural food sources of folate: dark leafy greens, asparagus, Brussels sprouts, lentils, chickpeas, and avocado.
  • Balance dietary B vitamins: include foods rich in B2 (riboflavin), B6 (pyridoxine), and B12 (cobalamin). Good sources are eggs, lean meats, poultry, dairy, fortified whole grains, nuts, and seeds.
  • Include choline sources to support methyl donation: eggs, organ meats, soybeans, and cruciferous vegetables contain choline or its precursors.
  • Maintain steady protein intake for serine and glycine precursors. Beans, legumes, lean animal protein, and dairy contribute to amino acid pools used by SHMT1.
  • Limit excessive alcohol and highly processed foods that can reduce B vitamin absorption and increase folate needs.

Supplement Considerations

Supplements can help when dietary intake is insufficient or increased needs exist. Consult your healthcare provider before starting any supplement.

  • Folate: If supplementing, consider methylfolate (5-MTHF) or folinic acid if recommended by your provider. Standard folic acid is widely used, but some individuals prefer bioactive folate forms.
  • Vitamin B12: Methylcobalamin or cyanocobalamin as directed. B12 supports the Methionine Cycle and helps keep homocysteine in check.
  • Vitamin B6 and B2: Pyridoxine and riboflavin support steps in one carbon metabolism and related enzymes.
  • Choline: Supplementation may help methylation support in people with low dietary intake.
  • Multivitamin: A balanced B vitamin complex with folate and B12 can provide broad support when diet is inconsistent.

Lifestyle and Practical Steps

  • Maintain a balanced, nutrient-rich diet. Small consistent food choices matter more than sporadic supplementation.
  • Aim for regular meal timing. Consistent intake of micronutrients supports steady one carbon metabolism.
  • Manage stress and get regular sleep. Stress and poor sleep can increase inflammatory and methylation demands.
  • Limit alcohol intake and smoking. Both increase nutrient needs and can impair folate status.
  • During pregnancy planning or pregnancy, ensure adequate folate intake according to provider guidance.

Lab Tests and Monitoring

  • Homocysteine: Elevated homocysteine can indicate functional insufficiencies in folate, B12, or B6 and helps assess methylation support.
  • Serum folate and red blood cell folate: These tests give short term and longer term folate status, respectively.
  • Vitamin B12 and methylmalonic acid (MMA): Useful to confirm B12 status.
  • Other nutrient panels: B2, B6, choline status, and comprehensive metabolic panels can be helpful if symptoms or risk factors exist.

When to Talk with Your Healthcare Provider

  • If you have symptoms like unexplained fatigue, neuropathy, cognitive changes, or a history of elevated homocysteine.
  • If you are pregnant or planning pregnancy and want personalized folate and B vitamin guidance.
  • If you have other genetic variants affecting one carbon metabolism or a medical condition that influences nutrient absorption.
  • Before starting supplements, especially if you take medications or have chronic health conditions.

PlexusDx does not provide medical advice. This information is educational and describes genetic predispositions and general lifestyle, diet, and supplement options that may support one carbon metabolism. Always consult your healthcare provider for medical advice, diagnosis, or treatment tailored to your health history and current condition.

If this genetic variant is present in your PlexusDx results, the following tests and reports are commonly used to explore it further:

🧬 Genetic Tests:

🧪 Blood Tests:

📄 Genetic Report:

Frequently Asked Questions About Folate Cycle and SHMT1 rs1979277

How does the SHMT1 gene affect one carbon metabolism and methylation?

SHMT1 encodes serine hydroxymethyltransferase 1, an enzyme that supports folate-dependent one carbon metabolism by converting serine and tetrahydrofolate into glycine and 5,10-methylenetetrahydrofolate. These products help fuel DNA synthesis, support nucleotide balance, and provide methyl groups for the Methionine Cycle and methylation reactions. Proper SHMT1 function also contributes to healthy gene regulation, detoxification processes, and homocysteine balance.

What do SHMT1 rs1979277 genotypes (AA, AG, GG) commonly mean for my nutritional needs?

For rs1979277, the AA genotype involves an amino acid substitution, with literature showing mixed associations; AA is not consistently linked to clearly reduced SHMT1 activity, though some evidence suggests altered thymidylate synthase activity that may affect DNA synthesis demands. The AG genotype typically reflects near-normal enzyme activity, but can allow subtle shifts in folate intermediates under low dietary folate, high cell division, or higher methylation demand. The GG genotype is generally associated with typical SHMT1 activity, and standard dietary folate and B vitamin intake usually supports healthy methylation and nucleotide synthesis.

Which diet, supplement, and lab tests are most useful if I have an SHMT1 variant?

To support SHMT1-related one carbon metabolism, prioritize folate-rich foods (dark leafy greens, asparagus, Brussels sprouts, lentils, chickpeas, avocado), balance B vitamins (B2, B6, B12), include choline sources (eggs, organ meats, soybeans, cruciferous vegetables), and maintain steady protein intake for serine and glycine precursors. Supplement considerations may include methylfolate (5-MTHF) or folinic acid, B12 (methylcobalamin or cyanocobalamin), and B6/B2 as appropriate—ideally guided by a healthcare provider. For monitoring, consider homocysteine, serum folate and red blood cell folate, and B12 status with methylmalonic acid (MMA) if needed; additional nutrient panels (B2, B6, choline) may be useful based on symptoms or risk factors.

What tests can help me learn more about Folate Cycle and SHMT1 rs1979277?

The Genetic Methylation Test delivers over 300 genetic insights related to methylation, detoxification, and nutrient processing. The Methylation Pathway Genetic Report translates your results into personalized, actionable guidance. Your healthcare provider can also recommend targeted blood tests based on your specific pathway results and health history to complement your genetic insights with current biomarker data.

Medical and Editorial Standards

Medical review process: This article was reviewed for medical accuracy, scientific clarity, evidence alignment, and appropriate discussion of genetics, medications, supplements, biomarkers, and health-related claims.

Sources and evidence: PlexusDx educational content is developed using peer-reviewed research, clinical literature, reputable medical references, and, where applicable, public health or regulatory guidance. References are included at the end of the article when scientific, medical, or health-related claims are discussed.

Commercial transparency: PlexusDx offers genetic testing, blood biomarker testing, personalized supplement recommendations, and related precision wellness services. Product mentions are intended to help readers understand available options and should not be interpreted as medical advice.

Important disclaimer: PlexusDx educational content is for informational purposes only and should not be used as a substitute for professional medical advice, diagnosis, or treatment. Always consult a qualified healthcare provider before making decisions about medications, supplements, genetic testing, lab testing, or health-related care.