FUT2 (fucosyltransferase 2) is a protein-encoding gene; it instructs your body to create an enzyme called Galactoside 2-alpha-L-fucosyltransferase 2. It's better to have this gene increased most of the time.
We use this enzyme to produce glycans (fiber-like molecules) found in our saliva and in the mucus of our intestine. Nursing mothers use the enzyme to produce glycans in their milk, which are called human milk oligosaccharides. In saliva and mucus, the glycans are part of our body’s natural defense system. In mothers’ milk, they function as part of the mothers’ protection for her baby. The glycans found in saliva and mucus are chemically bound, while those in mothers’ milk are free or separate molecules.
You can be either a secretor or a nonsecretor depending on whether you secrete your blood type antigens into your body fluids, such as saliva, mucus (in the digestive tract and the respiratory cavities), tears, sweat, etc. In about 20% of the population, the FUT2 gene is altered. Due to this alteration, these people cannot produce the α1,2-fucosyltransferase enzyme.
If you have a functional FUT2 gene, then you are a secretor. This means that you secrete a soluble form of the H-antigen in your saliva and mucus, which can allow you to have a proper ABO blood type depending on your genetics.
If you carry the alteration in this gene, then you are a non-secretor, and this has been associated with a wide variety of diseases (like urinary tract infections, diabetes, digestive disorders, etc.)
If you are a non-secretor, then it is advisable to include probiotics into your daily choices, especially those containing the bifidobacterial strains. Ensuring that you have healthy estrogen levels is also important as estrogen increases FUT2 expression.