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.

Understanding Vitamin C and Your Genes

Vitamin C is an essential nutrient your body cannot make, so you must get it from food or supplements. It acts as an antioxidant, supports collagen production for healthy skin and connective tissues, helps the body absorb iron, and plays a role in immune function. The SLC23A1 gene helps manage Vitamin C levels by producing the SVCT1 transporter protein. SVCT1 helps absorb Vitamin C from the intestines and reabsorb it in the kidneys, affecting circulating vitamin C levels.

Why your SLC23A1 genotype matters

Small variations in the SLC23A1 gene can change how efficiently SVCT1 moves Vitamin C into and back into the bloodstream. That can influence how much Vitamin C you naturally maintain after eating or taking supplements. Knowing your genotype helps you personalize diet and lifestyle choices to support optimal Vitamin C status.

2 effect alleles (TT for rs12479919)

If your genotype is TT, you carry two copies of the effect allele. This variant is associated with higher plasma Vitamin C levels. Your SVCT1 transporter may work in a way that tends to increase absorption or retention of Vitamin C, so you may naturally maintain higher circulating Vitamin C concentrations than people with other genotypes.

Even with a genetic tendency toward higher Vitamin C, continuing to prioritize Vitamin C-rich foods is important. Natural food sources provide fiber, phytonutrients, and a balance of nutrients that support long term health.

  • Diet: Citrus fruits, strawberries, kiwi, bell peppers, broccoli, Brussels sprouts, kale, and papaya.
  • Supplements: Likely not required if you have a balanced diet. If you take supplements, moderate doses such as 100 to 500 mg daily are usually adequate. Avoid very high doses without medical supervision.
  • Lifestyle: Manage stress, avoid heavy smoking or excessive alcohol, and maintain a varied whole food diet to support antioxidant balance.
  • Monitoring: Routine blood tests are generally not necessary solely for Vitamin C in healthy people, but discuss testing with your clinician if you have medical conditions or symptoms of deficiency.
1 effect allele (CT for rs12479919)

If your genotype is CT, you carry one copy of the effect allele. This is associated with likely higher plasma Vitamin C levels compared to the typical population. Your SVCT1 transporter may have slightly enhanced absorption or reabsorption, helping you maintain higher circulating Vitamin C than people without the effect allele.

Continue regular intake of Vitamin C-rich foods to support collagen, immune health, and iron absorption.

  • Diet: Aim for at least 2 to 3 servings per day of fruits and vegetables high in Vitamin C, such as citrus, berries, peppers, and cruciferous vegetables.
  • Supplements: Not usually necessary if dietary intake is adequate. Consider a low to moderate supplement if intake is inconsistent, especially during periods of high stress or illness.
  • Lifestyle: Maintain regular physical activity, get adequate sleep, and reduce exposure to smoking to preserve Vitamin C levels.
  • Monitoring: Consider discussing Vitamin C measurement with your provider if you have symptoms like easy bruising, slow wound healing, or if you have conditions that increase nutrient needs.
0 effect alleles (CC for rs12479919)

If your genotype is CC, you carry two copies of the non-effect allele. This is associated with typical Vitamin C absorption and retention through SVCT1 function. Your transporter likely operates in the usual range for absorbing Vitamin C from food and reabsorbing it in the kidneys.

Because the body does not store Vitamin C long term, consistent daily intake is important to maintain adequate levels.

  • Diet: Prioritize a variety of Vitamin C-rich foods daily: citrus fruits, strawberries, kiwi, bell peppers, broccoli, kale, and tomatoes.
  • Supplements: Consider a supplement if your diet is low in fruits and vegetables, during illness, or when increased needs are present. Typical supplemental doses range from 50 to 500 mg daily depending on need and tolerance.
  • Lifestyle: Reduce refined sugars, avoid smoking, and manage chronic stress which can deplete Vitamin C.
  • Monitoring: If you suspect low intake or have symptoms of deficiency discuss testing and management with your healthcare provider.

Practical diet recommendations

  • Daily servings: Aim for at least 5 servings of colorful fruits and vegetables daily. One medium orange, one cup of strawberries, or one cup of chopped bell pepper are good single-serving examples rich in Vitamin C.
  • Meal ideas: Add berries to yogurt or oatmeal, toss raw bell peppers or tomatoes into salads, steam broccoli or Brussels sprouts as a side, and use citrus-based dressings to boost intake.
  • Cooking tips: Vitamin C is heat sensitive. Use light steaming, raw preparations, or add vitamin C–rich foods at the end of cooking to preserve content.

Supplement guidance

  • When to consider supplements: If your diet lacks fruits and vegetables, during illness, or when increased needs are present such as recovery from surgery or in heavy smokers.
  • Typical dosing: Low to moderate supplemental doses commonly range from 50 to 500 mg daily. Very high doses can cause digestive upset and are not routinely necessary.
  • Formulations: Ascorbic acid is common. Liposomal or buffered forms may be gentler for sensitive stomachs. Discuss long term use and appropriate dose with your healthcare provider.

Lifestyle factors that affect Vitamin C

  • Smoking increases oxidative stress and depletes Vitamin C. Smokers often need higher intake to reach the same blood levels as non smokers.
  • Chronic stress can alter nutrient needs. Prioritize sleep, stress management, and regular exercise.
  • Heavy alcohol use can impair nutrient absorption. Moderate alcohol and prioritize nutrient dense foods.
  • Certain medical conditions and some medications can change nutrient requirements. Review these with your clinician.

When to talk with your healthcare provider

  • If you have symptoms like frequent bruising, slow wound healing, gum problems, or unexplained fatigue.
  • If you have a restrictive diet, gastrointestinal disorders that impair absorption, or chronic diseases that may change nutrient needs.
  • Before starting high dose Vitamin C supplements, especially if you have kidney stones, kidney disease, hemochromatosis, or take medications that interact with vitamin C.

Limitations and important disclaimer

This information is educational and based on genetic tendencies related to SLC23A1 and Vitamin C. PlexusDx does not provide medical advice. Genetic results describe predispositions and do not diagnose conditions or guarantee outcomes. Always consult your healthcare provider before making significant changes to diet, lifestyle, or supplements, or if you have health concerns. Your clinician can consider your genotype together with medical history, medications, and lab tests to make personalized recommendations.

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 Vitamin C and SLC23A1 rs12479919

How does the SLC23A1 rs12479919 variant affect my vitamin C levels?

The SLC23A1 gene helps control vitamin C status by producing the SVCT1 transporter that absorbs vitamin C from the intestines and reabsorbs it in the kidneys. Small differences in SLC23A1 (rs12479919) may change how efficiently SVCT1 moves vitamin C into and back into the bloodstream, which can influence how much vitamin C you tend to maintain after eating or supplementing.

What vitamin C intake is recommended for TT, CT, or CC genotypes for rs12479919?

TT (two effect alleles) is associated with higher plasma vitamin C levels, but you should still prioritize vitamin C-rich foods for long-term support. CT (one effect allele) is associated with likely higher plasma vitamin C and may benefit from regular intake of fruits and vegetables high in vitamin C. CC (zero effect alleles) is associated with typical absorption and retention, so consistent daily intake matters. If dietary intake is low, supplements may be considered at low to moderate doses (often 50 to 500 mg daily), unless a clinician advises otherwise.

When should I consider vitamin C supplements or talk to my healthcare provider?

Consider supplements if your diet lacks fruits and vegetables, during illness, recovery from surgery, or in situations that increase needs (such as heavy smoking). Typical supplemental doses are often 50 to 500 mg daily, and very high doses are usually unnecessary and may cause digestive upset. Talk to your healthcare provider if you have symptoms of low vitamin C (e.g., frequent bruising, slow wound healing, gum issues, unexplained fatigue), if you have conditions or medications that affect nutrient needs/absorption, or before high-dose use—especially if you have kidney stones, kidney disease, hemochromatosis, or take interacting medications.

What tests can help me learn more about Vitamin C and SLC23A1 rs12479919?

The Optimal Diet and Weight Loss Genetic Test delivers over 295 genetic insights related to nutrition response, body composition, metabolism, and fitness. The Diet and Nutrition 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.