Transsulfuration | CBS (rs2851391)

If you have the TT genotype at rs2851391, you carry two copies of the effect allele. This is commonly associated with reduced CBS enzyme activity. Reduced CBS function can slow the conversion of homocysteine into cystathionine, potentially leading to higher homocysteine and decreased production of cysteine and glutathione.

Potential implications

• Elevated homocysteine under certain conditions, which can stress methylation pathways
• Lower glutathione synthesis, increasing vulnerability to oxidative stress
• Possible sensitivity to high sulfur intake or impaired ammonia handling in some individuals

Diet recommendations

• Include foods rich in vitamin B6 (poultry, fish, bananas, chickpeas), folate (leafy greens, legumes), and B12 (animal products or fortified foods) to support methylation and CBS cofactors.
• Eat sulfur-containing foods (eggs, cruciferous vegetables, garlic, onions) in moderation if you notice sensitivity such as increased gas, headaches, or other symptoms.
• Prioritize antioxidant-rich foods: berries, dark leafy greens, colorful vegetables, nuts, and seeds to help offset lower glutathione.
• Choose lean protein sources and whole grains to maintain steady methyl donor availability.

Supplement recommendations (discuss with your clinician)

• Vitamin B6 (pyridoxal-5-phosphate preferred) to support CBS enzymatic activity
• Folate (preferably 5-MTHF if indicated) and vitamin B12 to support remethylation pathways
• Betaine (trimethylglycine) to assist alternative homocysteine clearance
• Antioxidants: N-acetylcysteine or precursors that support glutathione when appropriate; vitamin C and E as complementary antioxidants
• Consider lower doses and titration under supervision if you have marked sulfur sensitivity

Lifestyle and other considerations

• Reduce chronic stress and improve sleep to protect methylation efficiency
• Avoid excessive alcohol and smoking, which deplete cofactors and increase oxidative load
• Support gut health with a fiber-rich diet, probiotics, and appropriate treatment for dysbiosis, since the gut influences sulfur metabolism and ammonia handling

Suggested lab tests to discuss with your provider

• Plasma homocysteine
• Serum B6, folate, and B12 levels
• Liver function and ammonia if clinically indicated
• Markers of oxidative stress or glutathione status when available

If you have the CT genotype, you carry one effect allele and one non-effect allele. This pattern is often associated with intermediate CBS enzyme efficiency. Under normal circumstances your transsulfuration and methylation pathways may function adequately, but efficiency can decline with stress, inflammation, poor diet, or low nutrient status.

Potential implications

• Possible moderate risk for elevated homocysteine during periods of increased demand
• May benefit from proactive nutrient support and lifestyle measures to prevent imbalance

Diet recommendations

• Maintain consistent intake of B6, folate, and B12 rich foods
• Include antioxidant-rich fruits and vegetables to protect against oxidative stress
• Monitor responses to high-sulfur foods and adjust portioning if you experience intolerance

Supplement recommendations (discuss with your clinician)

• Moderate vitamin B6 support as needed
• Ensure adequate folate and B12; consider 5-MTHF for folate support if appropriate
• Consider betaine if homocysteine is elevated or if advised by your provider
• General antioxidant support such as vitamin C, vitamin E, or dietary polyphenols

Lifestyle and testing

• Manage stress, prioritize sleep, and reduce exposures that increase oxidative burden
• Check homocysteine and B vitamin status during routine care if there are symptoms or other risk factors

If you have the CC genotype, you carry two copies of the non-effect allele and are generally associated with normal CBS enzyme activity. Your transsulfuration pathway is typically able to convert homocysteine into cystathionine effectively, supporting cysteine and glutathione production when nutrient intake is adequate.

Potential implications

• Lower likelihood of CBS-related impairment of homocysteine clearance under normal conditions
• Standard recommendations to support methylation and antioxidant status remain valuable

Diet and supplement guidance

• Consume a balanced diet with sufficient B6, folate, and B12 to maintain methylation support
• Eat antioxidant-rich foods to support glutathione and overall detoxification
• Supplement only based on clinical need and testing

Lifestyle

• Maintain healthy sleep, stress management, and avoidance of excess alcohol or smoking
• Routine monitoring of homocysteine and B-vitamin status if risk factors develop