The association is established; acting on it is not advised
One of the clearest gene–nutrient links there is, and it works through the gut lining rather than through anything on the label. It still does not tell anyone to take a supplement.
Solid lines are connections this site curates. Dashed lines mean the two ends share a research paper — worth knowing, and not a claim that one explains the other.
FUT2 decides whether you are a "secretor" — whether the blood-group sugars on your cells are also secreted into saliva, tears and the mucus lining the gut. A large minority of people are non-secretors, and it is one of the most common functional differences in the human genome.
A 2008 genome-wide scan of 1,658 people, replicated in an independent 1,059, found a FUT2 variant associated with plasma vitamin B12 at p = 5.4 × 10⁻¹⁷. It is in strong linkage disequilibrium with the non-secretor change, which points at a mechanism rather than a coincidence: the gut lining is where B12 is absorbed, and it is also what secretor status changes.
So this is a real, replicated, mechanistically plausible effect on a blood level. What it is not is a reason to buy anything. B12 status is measured directly and cheaply, deficiency is diagnosed and treated on that measurement, and no guideline sets a dose from a genotype. The people who actually need B12 — after certain gut surgery, on long-term metformin, on a strict vegan diet, or with pernicious anaemia — need it whatever their FUT2 result says.
See also FUT2 secretor status, where the same gene turns up in resistance to norovirus.
Vitamin B12 is a nutrient needed for making red blood cells and maintaining nerve function, absorbed through a specific process in the gut. A gene tied to gut lining function affects how well some people absorb it.
Not by itself. B12 status is measured directly and cheaply, and deficiency is diagnosed and treated on that measurement, not on genotype.
People after certain gut surgery, on long-term metformin, on a strict vegan diet, or with pernicious anaemia need it whatever their FUT2 result says.
Yes — the same gene affects resistance to norovirus, covered on this site's FUT2 secretor status condition page.
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Vitamin B12. MyGeneLog™. https://www.mygenelog.com/supplements/vitamin-b12
Nothing on this page recommends taking anything. If a result here matters to you, take it to a doctor or a pharmacist rather than to a shop.