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How Riboflavin (Vitamin B2) and FMO3 Genetics Affect Your Health

Riboflavin, also known as Vitamin B2, is an essential nutrient that helps convert food into usable energy and supports healthy skin, eyes, and the nervous system. It contributes to red blood cell production and acts as an antioxidant. Riboflavin also forms flavin adenine dinucleotide, or FAD, a molecule that supports several enzymes in the liver including FMO3.

The FMO3 gene encodes an enzyme that helps break down certain nitrogen-containing compounds produced during digestion and by gut bacteria. One of these compounds is trimethylamine, which can have a fishy odor if not converted into its harmless form. Variations in the FMO3 gene can reduce how well this enzyme works. Because FAD is a cofactor for FMO3, sufficient riboflavin intake may support its activity.

What this means for you

Your FMO3 genotype influences how efficiently your body handles certain dietary compounds. Regardless of genotype, riboflavin remains important for overall energy metabolism and enzyme function. The sections below explain typical effects by genotype and practical steps to support FMO3 function, digestion, and general wellness.

2 effect alleles (TT for rs909530) — decreased FMO3 function

If your genotype is TT at rs909530, you carry two copies of the effect allele. This is linked to decreased FMO3 enzyme function. Reduced activity may make conversion of trimethylamine to its odorless form less efficient, potentially increasing buildup of this compound under some conditions.

Practical recommendations

  • Diet: Emphasize riboflavin-rich foods daily — dairy, eggs, lean meats (such as poultry and fish), mushrooms, almonds, spinach, and fortified cereals. Because riboflavin is water-soluble, regular intake matters.
  • Supplements: Consider a riboflavin supplement if dietary intake is low or if a healthcare provider recommends it. Typical supplemental doses range from 1.3 mg to higher therapeutic doses used in some settings, but discuss appropriate dosing with your provider first.
  • Gut health: Support a balanced microbiome with fiber-rich foods, fermented foods if tolerated, and a varied diet to reduce excessive production of trimethylamine from gut bacteria.
  • Hydration and liver support: Maintain good hydration and avoid excessive alcohol. Regular checkups with your healthcare provider can monitor liver health if there are concerns.
  • Food triggers: Some people notice stronger odors after eating foods high in choline or carnitine (for example, large portions of eggs, red meat, or certain fish). Moderating those foods and spreading intake through the day may help.
  • When to see a provider: If unusual body or urine odor is persistent or causes distress, consult a healthcare provider for evaluation and to rule out other causes.
1 effect allele (CT for rs909530) — slightly decreased FMO3 function

If your genotype is CT, you carry one copy of the effect allele and one copy of the non-effect allele. This is typically associated with a mild decrease in FMO3 function compared with the typical population. Most people with this genotype do not experience significant issues, but supporting FMO3 with riboflavin and healthy habits can be beneficial.

Practical recommendations

  • Diet: Include riboflavin-rich foods every day — dairy, eggs, lean meats, mushrooms, almonds, spinach, and fortified grains. Small, consistent servings are effective because riboflavin is not stored long term.
  • Supplements: If intake from food is limited, discuss a low-to-moderate riboflavin supplement with your healthcare provider. Also consider a balanced B-complex if multiple B vitamins are low.
  • Balance gut bacteria: Eat a variety of fiber-containing vegetables, whole grains, and fermented foods when appropriate to encourage a healthy microbiome that produces fewer odor-producing compounds.
  • Lifestyle: Manage alcohol intake, get adequate sleep, and maintain a healthy body weight to support liver function and overall metabolism.
  • Monitoring: If you notice changes in body odor after specific foods or during illness, tracking patterns and discussing them with a provider can help identify triggers and solutions.
0 effect alleles (CC for rs909530) — typical FMO3 function

If your genotype is CC, you carry two copies of the non-effect allele and are expected to have typical FMO3 enzyme function. Your body should be able to convert trimethylamine into its harmless form effectively under normal conditions.

Practical recommendations

  • Diet: Continue to include riboflavin-rich foods as part of a balanced diet — dairy, eggs, lean meats, mushrooms, almonds, spinach, and fortified cereals help maintain FAD levels and support enzyme function.
  • Supplements: Most people with normal enzyme function can meet needs through diet. Discuss supplements with a healthcare provider before starting them.
  • Healthy habits: Maintain a varied, fiber-rich diet, regular exercise, moderate alcohol, and good sleep to support liver and gut health.
  • Awareness: Even with typical FMO3 function, very large intakes of choline or carnitine or changes in gut bacteria can alter production of trimethylamine, so moderation and dietary variety remain sensible.

Additional lifestyle and testing considerations

  • Blood tests: Routine labs ordered by your healthcare provider can assess general liver function and nutritional status if there are concerns about vitamin levels or liver health.
  • Dietary pattern: A nutrient-dense, varied diet reduces risk of deficiency and supports the enzymes that rely on vitamins like riboflavin. Aim for balanced meals that include protein, vegetables, whole grains, and healthy fats.
  • Supplement quality: If a supplement is recommended, choose products from reputable manufacturers and discuss interactions with any medications with your healthcare provider.
  • When to seek care: Persistent or distressing body odor, sudden changes in odor, or other unexplained symptoms should be evaluated by a healthcare professional.

PlexusDx provides genetic information to help you understand predispositions and inform discussions with your healthcare team. This information is educational only and does not replace medical advice, diagnosis, or treatment. Always consult your healthcare provider before making changes to diet, supplements, or lifestyle based on genetic results.