The FUT2 gene determines if an individual is a “secretor” or a “non-secretor,” a status with significant implications for personal health. This distinction lies in the presence or absence of specific molecules in bodily fluids, a difference rooted in the gene’s function. This genetic variation shapes aspects of immunity and gut health.
The Secretor Status Gene
The FUT2 gene (Fucosyltransferase 2) provides instructions for an enzyme that attaches a sugar molecule, fucose, to a precursor substance to create the H antigen. In people with a functioning FUT2 gene, H antigens are present on red blood cells and are also secreted into bodily fluids. These fluids include saliva, tears, and the mucus lining the digestive tract.
People with a functional copy of the gene are “secretors.” In their mucus, the H antigen is modified to match their ABO blood type, so a person with type A blood will have A antigens in their gut lining. Approximately 80% of some populations are secretors.
“Non-secretors” possess a non-functional version of the FUT2 gene, often due to a specific genetic variation (SNP rs601338). They do not produce the H antigen in their mucosal linings or secrete their blood type antigens into these fluids. This accounts for about 20% of the population.
Impact on the Gut Microbiome
Secreted blood group antigens directly shape the gut’s microbial community. For secretors, these complex carbohydrates function as a built-in food source, or prebiotic, for certain types of bacteria. This selectively encourages the growth of beneficial microbes that can consume these sugar structures.
This genetic distinction creates a noticeable difference in microbiome composition. Secretors tend to have significantly higher populations of Bifidobacteria. These bacteria are well-equipped to consume the H antigen and related blood type molecules, allowing them to flourish in a secretor’s gut.
In contrast, a non-secretor’s gut lacks this specific food source, leading to lower levels of Bifidobacteria and a different overall microbial landscape. Other bacterial species fill the niches that Bifidobacteria would otherwise occupy.
Health Implications of FUT2 Variation
Non-secretors exhibit a natural resistance to the most common strains of norovirus, the virus responsible for most epidemic gastroenteritis. The virus uses the H antigen to attach to gut cells. Since non-secretors lack this antigen in their gut lining, the virus cannot effectively establish an infection.
This same mechanism, however, can alter susceptibility to other microbes. Some studies suggest non-secretors may have more issues with Candida yeast overgrowth or infections from bacteria like H. pylori.
Non-secretor status is also associated with an increased risk of developing chronic inflammatory and autoimmune conditions. Studies have identified a link between this status and a higher likelihood of developing Crohn’s disease, other forms of inflammatory bowel disease (IBD), and Type 1 diabetes. The altered gut microbiome in non-secretors may contribute to the chronic inflammation that underlies these conditions.
Being a non-secretor is also associated with a higher risk for Vitamin B12 deficiency. The mechanism is believed to be connected to the altered gut environment. The bacterial populations fostered by secretor status may play a part in the synthesis or absorption of this vitamin, and their absence in non-secretors could impair this process.
Identifying and Addressing Your Status
Your FUT2 secretor status can be determined through direct-to-consumer genetic testing services. These tests analyze a saliva sample for the specific genetic markers that show whether the FUT2 gene is functional. The results provide a clear answer as to whether you are a secretor or a non-secretor.
Understanding your status allows for more tailored dietary considerations. For non-secretors, a primary goal is to support beneficial bacteria by consuming foods rich in other types of prebiotics. These include fructo-oligosaccharides (FOS) and galacto-oligosaccharides (GOS), found in foods like chicory root, onions, garlic, and legumes, which help feed bacteria like Bifidobacteria.
Probiotic supplements containing specific strains of Bifidobacteria may also be a supportive strategy for non-secretors. Given their increased risk for lower Vitamin B12 levels, non-secretors should also be mindful of their B12 intake and consider regular monitoring. For secretors, maintaining general gut-healthy practices like a diverse, fiber-rich diet remains important.