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Understanding Your SUOX Gene Result: How Sulfite Oxidase Affects Sulfur Metabolism

The SUOX gene makes sulfite oxidase, a molybdenum-dependent enzyme that performs a crucial final step in the transsulfuration pathway. This enzyme converts sulfite, a potentially harmful intermediate formed when the body breaks down sulfur-containing amino acids like cysteine and methionine, into harmless sulfate. Proper SUOX function helps maintain sulfur balance, supports glutathione production and methylation processes, and prevents buildup of toxic sulfites that can cause oxidative stress, respiratory irritation, and chemical sensitivities.

This article explains what different genotypes for rs705703 may mean for SUOX activity, practical ways to support healthy sulfur metabolism, and lifestyle and testing considerations to help you work with your healthcare provider. PlexusDx does not provide medical advice. Always consult your healthcare provider before making changes to diet, supplements, or treatment.

How SUOX Fits into Methylation and Transsulfuration

The transsulfuration pathway diverts homocysteine into glutathione and other sulfur metabolites. When enzymes earlier in this pathway are highly active, sulfite levels can rise. SUOX is the final detoxifier in this chain. If SUOX is less efficient or if molybdenum is low, sulfite can accumulate and place additional stress on detoxification, antioxidant defenses, and mitochondrial function.

Potential Symptoms of Elevated Sulfite

  • Respiratory irritation, wheeze, or asthma-like symptoms after exposure to sulfite-containing foods or preservatives
  • Heightened sensitivity to sulfur-rich supplements or foods
  • Fatigue or neurological symptoms in some people when sulfite clearance is impaired
  • Increased oxidative stress and reduced detoxification capacity

Genetic Interpretation

Two effect alleles (TT) — Reduced SUOX activity

You have two copies of the effect allele at rs705703 (TT). This genotype is associated with reduced sulfite oxidase activity. With lower SUOX function, your ability to convert sulfite to sulfate may be compromised, increasing the risk of sulfite accumulation when sulfur intake is high or when other parts of the transsulfuration pathway are active.

Actionable considerations

  • Work with your clinician to evaluate symptoms suggestive of sulfite sensitivity.
  • Consider a trial of molybdenum supplementation under medical supervision, as molybdenum is a required cofactor for SUOX.
  • Support antioxidants and mitochondrial function with nutrients such as vitamin C, N-acetylcysteine when appropriate, and B vitamins to help overall methylation and glutathione synthesis.
  • Monitor and moderate intake of sulfur-rich foods and supplements if you notice intolerance. Examples include high-dose N-acetylcysteine, taurine, MSM, onion, garlic, cruciferous vegetables, and certain protein powders.
  • Discuss lab testing with your provider if indicated, including plasma sulfite or sulfate measures, molybdenum status evaluation, and markers of oxidative stress or mitochondrial function.
One effect allele (CT) — Intermediate SUOX activity

You carry one effect allele and one non-effect allele at rs705703 (CT). This intermediate genotype can be associated with mildly reduced SUOX activity in some people. Many with CT maintain adequate sulfite clearance, but you may be more likely than CC carriers to notice sensitivity under high sulfur intake or oxidative stress.

Actionable considerations

  • Maintain a balanced diet and observe how you tolerate sulfur-containing foods and supplements. Adjust intake based on personal tolerance.
  • Ensure adequate molybdenum intake through diet or low-dose supplementation if recommended by your provider. Foods containing molybdenum include legumes, whole grains, and organ meats.
  • Support glutathione synthesis and antioxidant defenses with adequate B vitamins (B2, B6, B9, B12), vitamin C, and dietary precursors when appropriate.
  • Limit exposure to sulfite preservatives in processed foods if you notice respiratory or allergic-type reactions.
  • Consider periodic review with your clinician if you plan to use high-dose sulfur supplements or have symptoms that may relate to sulfite sensitivity.
Zero effect alleles (CC) — Typical SUOX activity

You have two copies of the non-effect allele at rs705703 (CC). This genotype is associated with normal SUOX enzyme function. With efficient conversion of sulfite to sulfate, your body is generally well-equipped to handle dietary sulfur and to prevent sulfite buildup.

Actionable considerations

  • Maintain a balanced diet that supports methylation and transsulfuration with adequate protein, B vitamins, and trace minerals including molybdenum.
  • Antioxidant support through a diet rich in fruits, vegetables, and sources of vitamin C and E helps sustain detoxification pathways.
  • If you plan to use high-dose sulfur supplements, monitor how you feel and consult your healthcare provider to ensure these are appropriate for you.
  • Routine wellness checks are usually sufficient unless symptoms of sulfite sensitivity appear.

Dietary Recommendations

  • Emphasize whole foods: vegetables, fruits, lean proteins, legumes, nuts, and whole grains to support methylation and antioxidant capacity.
  • Moderate sulfur-rich foods if you are sensitive: reduce high amounts of garlic, onion, cruciferous vegetables, eggs, and high-dose sulfur supplements while monitoring symptoms.
  • Include molybdenum-containing foods: legumes, whole grains, nuts, and organ meats. If dietary intake is low, discuss low-dose molybdenum supplementation with your clinician.
  • Ensure adequate intake of B vitamins through food or supplements if recommended, as they support homocysteine balance and glutathione production.

Supplement and Lifestyle Suggestions

  • Molybdenum: Consider assessment and possibly low-dose supplementation if indicated by symptoms or testing, under medical supervision.
  • Antioxidants: Vitamin C and other antioxidants can help neutralize oxidative stress associated with sulfite accumulation.
  • Support glutathione and mitochondria: Nutrients such as N-acetylcysteine, alpha-lipoic acid, coenzyme Q10, and adequate B vitamins may be helpful when used appropriately and supervised by your provider.
  • Avoid unnecessary exposure to sulfite preservatives in foods and beverages if you experience sensitivity.
  • Reduce inflammatory and oxidative burden with regular sleep, stress management, moderate exercise, and minimizing tobacco and excessive alcohol use.

When to Talk to Your Healthcare Provider

  • If you experience respiratory symptoms, hives, worsening asthma, or neurological symptoms after eating sulfur-containing foods or taking supplements
  • If you plan to start high-dose sulfur supplements, molybdenum, or powerful antioxidant protocols
  • If you have complex metabolic or mitochondrial concerns that may intersect with sulfite handling
  • To arrange laboratory testing or professional evaluation of molybdenum status, sulfite/sulfate balance, and related metabolic markers

Important Disclaimer

PlexusDx provides genetic information to educate about predispositions and potential strategies to support metabolic health. This content is not medical advice. Always consult your healthcare provider before making changes to diet, supplements, medications, or treatment plans. Genetic information is one piece of your overall health picture and should be interpreted alongside clinical evaluation and laboratory testing.