Nutrient Bioavailability — Genes & Biomarkers Gene / Biomarker Suboptimal / Limiting Factor Free Actions Non-free Actions GENES (6) MTHFRImpaired folate methylationLeafy greens, no alcoholMethylfolate 5-MTHF VDRLow vitamin D sensitivitySun exposure, fatty fishVitamin D3 + K2 BCMO1Poor beta-carotene conversionLiver, eggs, dairyRetinol supplement FUT2Poor B12 absorptionFermented foods, meatMethylcobalamin HFEIron overload riskTea with meals, avoid suppl.Ferritin test, phlebotomy FADS1/2Poor omega-3/6 conversionFatty fish, less seed oilEPA+DHA supplement BIOMARKERS (7) Vitamin D <30 ng/mLLow sun or intakeSun, mushrooms, fatty fishVitamin D3 supplement Ferritin <30 µg/LIron deficiencyIron-rich foods + vitamin CIron bisglycinate B12 <300 pg/mLMalabsorption or vegan dietAnimal products, yeastMethylcobalamin Folate <5 ng/mLLow intake or MTHFRLegumes, leafy greens5-MTHF supplement Homocysteine >10 µmol/LB-vitamin dysfunctionB-rich diet, low methionineB6 + B9 + B12 complex Omega-3 index <8%Low fatty fish intakeFatty fish 3x/weekFish oil EPA+DHA Retinol <40 µg/dLLow intake or conversionLiver, eggs, colorful veggiesRetinol supplement