Vitamin A Conversion Efficiency

BCMO1 codes for beta-carotene 15,15'-monooxygenase, the intestinal enzyme that converts plant-based beta-carotene into retinal, the precursor of active vitamin A. Without efficient BCMO1, the orange and dark-green vegetables that should deliver vitamin A do so far less effectively.

Carriers of common BCMO1 reduced-activity variants (some studies estimate ~45% of people carry at least one) are associated with significantly lower conversion of dietary beta-carotene to active vitamin A, sometimes under half of typical efficiency. Carriers tend to show plant-based vitamin A insufficiency symptoms (night-vision changes, dry skin, slow immune recovery) despite eating plenty of carrots and sweet potatoes.

Preformed retinol from animal sources (liver, egg yolks, dairy fat, fatty fish) bypasses the conversion step entirely and is the most direct way to support tissue vitamin A in reduced-conversion carriers. Cooking and pairing carotene-rich foods with dietary fat improves whatever absorption does happen. Zinc, iron, and thyroid status all influence conversion.

"Get your vitamin A from sweet potatoes" works for typical-function carriers and falls short for reduced-function ones. Which BCMO1 variant you carry decides whether plant sources cover the need or whether dietary retinol is the more reliable input.