SLC23A1 rs3811803: Vitamin C Transport and Levels
The rs3811803 single-nucleotide polymorphism is a common genetic variant located within the SLC23A1 gene, which encodes the sodium-dependent vitamin C transporter 1 (SVCT1). In nutrigenomics research, this polymorphism has been studied for its association with circulating ascorbic acid concentrations and variations in intestinal absorption. The overall clinical and predictive evidence remains limited, reflecting statistical associations across study cohorts rather than a definitive medical condition.
What each genotype means
Typical vitamin C transport
This genotype represents the common version of the SLC23A1 gene associated with standard vitamin C transport efficiency. Research suggests individuals with this profile generally maintain typical circulating ascorbic acid levels, though individual dietary needs can still vary based on lifestyle and other genetic factors.
This is the most common genotype in most global populations.
Potential reduced transport efficiency
Carrying one copy of the G allele has been associated in some studies with slightly lower plasma vitamin C concentrations compared to the AA genotype. Because this variant influences how your body absorbs and distributes vitamin C, you may wish to discuss your dietary intake and nutritional status with a healthcare provider or registered dietitian.
This genotype is observed in a significant portion of the population, with the minor allele frequency reported at approximately 5-10% in European ancestry cohorts.
Likely reduced transport efficiency
Individuals with this genotype may experience reduced efficiency in the sodium-dependent transport of vitamin C, which can correlate with lower circulating levels of the vitamin. While this association is documented, it is important to remember that many factors influence nutrient status; please consult with a clinician to determine if your dietary vitamin C intake is appropriate for your needs.
This is the less common genotype, occurring in a smaller percentage of individuals consistent with the minor allele frequency of 5-10% in European populations.
What Is rs3811803 and Where Is It Located?
The single-nucleotide polymorphism rs3811803 represents an inherited single-letter DNA variation mapped to the solute carrier family 23 member 1 gene (SLC23A1) on chromosome 5. SLC23A1 codes for sodium-dependent vitamin C transporter 1 (SVCT1), an essential membrane transport protein. Unlike rare, disruptive mutations that cause monogenic disorders, rs3811803 is a common polymorphic marker evaluated in population genetics and nutrigenomics. It is indexed in major reference repositories, including the National Center for Biotechnology Information's [dbSNP database](https://www.ncbi.nlm.nih.gov/snp/rs3811803), where researchers monitor its genomic position, surrounding sequence context, and allele frequencies across global demographic groups. Within nutritional genomics cohorts, the variant serves as a genetic marker to explore how inherited diversity might contribute to inter-individual variations in vitamin C metabolism and physiological handling.
Biological Function of SLC23A1 and Vitamin C Uptake
The protein product of SLC23A1, SVCT1, plays a foundational role in human physiology by mediating the active, sodium-dependent cellular uptake of L-ascorbic acid, commonly known as vitamin C. SVCT1 is primarily expressed on the apical membranes of epithelial tissues, notably within the mucosal lining of the small intestine and the proximal tubules of the kidneys. Through this localized expression, SVCT1 facilitates both the intestinal absorption of dietary vitamin C and its active renal reabsorption to prevent excessive urinary excretion. Humans cannot synthesize ascorbic acid endogenously due to evolutionary mutations in the GULO gene, making effective transport across biological membranes necessary to maintain healthy systemic levels. By driving bulk transport across epithelial barriers, SVCT1 helps preserve ascorbic acid homeostasis, which supports endogenous antioxidant defenses, collagen synthesis, and enzymatic cofactor functions.
Scientific Evidence and Phenotypic Associations
Nutrigenomics research and genome-wide association investigations cataloged in resources like the [GWAS Catalog](https://www.ebi.ac.uk/gwas/search?query=SLC23A1) have evaluated polymorphisms within the SLC23A1 locus for their connection to baseline plasma ascorbic acid concentrations. Some observational studies indicate that carriers of the minor allele demonstrate modest statistical shifts in circulating vitamin C levels compared to non-carriers, prompting hypotheses that variation in transporter efficiency could influence individual dietary requirements. However, the scientific evidence supporting rs3811803 specifically remains categorized as limited. Findings across cohorts have shown variability, and statistical associations observed in population-level studies do not translate into predictable, clinically significant vitamin deficiencies. Large epidemiological analyses emphasize that direct dietary intake, smoking status, systemic inflammation, and metabolic factors generally exert a much stronger influence on circulating ascorbic acid levels than common individual variants.
Population Frequency and Ancestral Distribution
Allele frequencies for rs3811803 vary across different world populations, as documented in population genomic resources such as the [1000 Genomes Project](https://www.internationalgenome.org/) and the [Ensembl genome browser](https://www.ensembl.org/Homo_sapiens/Variation/Population?v=rs3811803). In European ancestry cohorts, the minor allele frequency is estimated to be approximately 5% to 10%, meaning that while the vast majority of individuals carry the common homozygous genotype, heterozygosity is relatively common. Frequencies can differ substantially among African, Asian, and Hispanic populations, reflecting ancestral evolutionary history and genetic drift. Because natural genetic variation is unequally distributed across ancestral groups, researchers caution against extrapolating statistical findings observed in predominantly European cohorts to other populations without direct validation in diverse demographic samples.
Practical Implications and Clinical Perspective
Discovering an individual genotype at rs3811803 provides interesting personal genomic context, but it does not represent a clinical diagnosis of vitamin C deficiency or scurvy. Because evidence linking this variant directly to adverse health outcomes is limited, a genetic finding alone cannot determine personal nutrient status or supersede standard nutritional guidelines. A healthy, balanced diet rich in varied fruits and vegetables—such as citrus fruits, bell peppers, broccoli, and berries—remains the established approach for maintaining adequate ascorbic acid levels regardless of genotype. Individuals should avoid using direct-to-consumer genetic data to initiate high-dose dietary supplementation without clinical oversight. Anyone with concerns about nutrient absorption, persistent deficiency symptoms, or specific dietary needs should review their dietary habits and consider routine laboratory testing with a qualified healthcare provider or registered dietitian.
How common is this variant?
The minor allele frequency for rs3811803 is approximately 5% to 10% in European ancestry cohorts, with the vast majority of individuals carrying the homozygous major genotype. Allele and genotype frequencies show variation across other continental ancestries, underscoring the importance of population-specific genomic contexts.
Frequently asked questions
Does having the rs3811803 minor allele mean I have scurvy or a vitamin deficiency?
No, carrying the minor allele does not mean you have or will develop scurvy or a clinical vitamin deficiency. The variant is simply a common genetic marker statistically associated with minor variations in circulating levels across large populations. Severe deficiency is caused by prolonged lack of dietary intake, not by this single polymorphism.
Can rs3811803 determine how much vitamin C I should take each day?
No, current scientific evidence is too limited to calculate specific personal milligram requirements based on this single-nucleotide polymorphism. Standard daily dietary reference intakes established by nutritional authorities remain the best guidance. Any decisions regarding targeted or high-dose supplementation should be discussed with a healthcare professional or registered dietitian.
How does the SLC23A1 gene work in the body?
SLC23A1 provides genetic instructions for creating SVCT1, a specialized membrane protein that uses sodium gradients to absorb vitamin C. It is located primarily in the lining of the small intestine to absorb dietary ascorbic acid and in the kidneys to reabsorb vitamin C before it is lost in urine.
What foods help maintain healthy vitamin C levels regardless of my genotype?
Consuming a variety of fresh produce easily provides sufficient daily ascorbic acid for most individuals. Excellent dietary sources include citrus fruits like oranges and grapefruits, strawberries, kiwi, bell peppers, tomatoes, and cruciferous vegetables like broccoli and Brussels sprouts.
Sources & further reading
Educational information only, last refreshed 9/5/2026. Not medical advice — these associations describe population statistics, not individual predictions.
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Transporter polymorphism associated with significant decrements in circulating ascorbic acid levels per unit of dietary vitamin C consumed.
This variant in the primary renal and intestinal sodium-dependent vitamin C transporter gene significantly modulates circulating ascorbic acid concentrations.