Eat your carrots. Eat your sweet potatoes. Spinach, kale, orange squash: all of them contain beta-carotene, which your body is supposed to convert into vitamin A. But for a large share of the population, that conversion is far less efficient than it sounds in textbooks. The gene responsible is BCMO1, and its common variants affect nearly half of all people.
How vitamin A actually works
Vitamin A exists in two forms in food. Preformed vitamin A (retinol) comes from animal products: liver, eggs, dairy and oily fish. It is absorbed directly and used immediately. Provitamin A carotenoids, the most important being beta-carotene, come from plants. They have to be converted to retinol inside the gut wall and liver before your body can use them. BCMO1 is the primary enzyme that does that conversion.
What BCMO1 variants do to your conversion rate
Two well-studied single nucleotide polymorphisms (SNPs) affect BCMO1 enzyme activity:
- rs12934922 (A379V): one copy reduces conversion efficiency by roughly 57 percent compared to the reference genotype. Two copies reduce it further.
- rs6564851 (R267S): independently associated with reduced BCMO1 activity and higher blood carotenoid levels (a sign the body is not converting them effectively).
Research published in the FASEB Journal found that women carrying two copies of rs12934922 had 69 percent lower beta-carotene conversion than those without the variant. Combined effects of multiple BCMO1 variants can push conversion capacity even lower. Estimates suggest that around 45 percent of the population carries at least one copy of a reducing variant, making this one of the most common nutritionally relevant genetic findings.
Who is most at risk
The conversion gap matters most for people who rely heavily on plant foods for vitamin A:
- Strict vegans and vegetarians who eat no animal products have no direct source of preformed vitamin A and depend entirely on BCMO1 conversion. If their BCMO1 is low-activity, blood retinol can fall even with a diet rich in colourful vegetables.
- Low-fat dieters: beta-carotene absorption from food requires dietary fat. Very low-fat meals substantially reduce how much carotene even reaches the conversion step.
- People with digestive issues: inflammatory bowel conditions, gut dysbiosis and fat malabsorption all reduce carotene uptake before BCMO1 even has a chance to act.
Symptoms of vitamin A insufficiency can include difficulty seeing in low light, dry skin, more frequent infections and slower wound healing, though these overlap with many other conditions and should be assessed medically before assuming a genetic cause.
What to do with this information
- Do not abandon vegetables. Even low-activity converters absorb some beta-carotene, and carotenoids have antioxidant value beyond their vitamin A role. The advice changes the emphasis, not the direction.
- Add preformed vitamin A sources. Eggs (yolk), full-fat dairy and oily fish provide retinol that bypasses BCMO1 entirely. Liver is the single richest source but should be consumed in moderation due to its very high retinol concentration.
- Cook vegetables in fat. Olive oil, avocado, nuts or any fat alongside carotene-rich vegetables dramatically increases how much carotene is absorbed from the gut.
- Consider a blood test. If you follow a predominantly plant-based diet and carry BCMO1 variants, a serum retinol test (not just beta-carotene) is the most direct way to know whether your levels are adequate. This is worth discussing with a dietitian or doctor.
Important: this article is educational and is not medical advice. Vitamin A supplementation carries a risk of toxicity at high doses, especially in pregnancy. Never start high-dose vitamin A supplements without medical supervision.
Discover your BCMO1 profile
The Fuel Your DNA Complete report reads your BCMO1 variants alongside more than 40 other genes covering vitamins, energy metabolism, inflammation and more. It translates your DNA into clear, personalised food guidance, using the raw file you already downloaded from your testing company. Get your Complete report or start with the free intolerance test.