Your genes control the species of bacteria that live in your gut microbiome. And your gut microbiome can help defend against — or make you vulnerable to — chronic diseases.
A genetic variant in the FUT2 gene controls whether or not you secrete your blood type into your saliva and other bodily fluids like the intestinal mucosa.
Whether you secrete your blood type plays a big role in the type of bacteria that dwell in our gut microbiome. Sounds crazy. But being a ‘non-secretor’ protects you from getting the norovirus – a.k.a. the dreaded stomach flu.
Researchers consider bifidobacteria to be one of the good guys when it comes to your gut microbiome. They are lactic and acetic acid producing bacteria that help keep your immune system in check.
Bifidobacteria break down carbohydrates (specifically, oligosaccharides) from the foods you eat. They also chow down on the oligosaccharides produced by our body in the intestinal mucosa. That is where secreting your blood type (an oligosaccharide) comes into play.[ref][ref]
Oligosaccharides are a carbohydrate that consists of three to nine monosaccharides (simple sugars). There are three types of oligosaccharides that act as prebiotics: fructooligosaccharides (FOS), galactooligosaccharides (GOS), and inulin. You can buy oligosaccharides as pre-biotic supplements or get them from foods like leeks, Jerusalem artichokes, onions, chicory root, and oats.
The FUT2 gene encodes the enzyme fucosyltransferase, which helps to form oligosaccharides.
Most people are familiar with the ABO blood type system and learned in high school biology about the A antigens and B antigens. These antigens (A and B) are actually a type of sugar molecule on the outside of the blood cell. The FUT2 gene comes into play when looking at the secretion of the blood type in bodily fluids such as saliva and intestinal mucosa.
The oligosaccharides secreted in the intestinal mucosa feed your intestinal flora, but not everyone secretes their blood type. In fact, about 20% of Caucasians are non-secretors.
A FUT2 non-secretor has a homozygous mutation in the SNP rs601338 that changes G to A. Those with A/G or G/G (heterozygous and wild-type) are FUT2 secretors.
Check your 23andMe results for rs601338 (v4, v5):
So what is the big deal about being a non-secretor? Well, it comes back to our bodies interactions with the microbiome. A 2011 study showed that individuals with the A/A allele on rs601338 (non-secretors) have significantly lower amounts of bifidobacteria in their gut microbiome. This makes sense because bifidobacteria are fed, in part, by the oligosaccharides in the intestinal mucosa. The same study showed that non-secretors actually had a higher diversity of bacteria. Another study in 2014 confirms those findings.
Non-secretors also often have higher serum B12 levels. This may not truly reflect the amount of B12 that is being transported into the cells, so a test of methylmalonic acid may give you a better indication of your B12 status. [ref]
An infants microbiome is, in part, colonized from the mother, and bifidobacteria usually make up a large part of an infant’s microbiome. Breastmilk contains oligosaccharides that feed the baby’s microbiome.
The effects on non-secretor status can also influence breastfed babies of non-secretor mothers. A 2015 study found that “Infants fed by non-secretor mothers are delayed in the establishment of a bifidobacteria-laden microbiota. This delay may be due to difficulties in the infant acquiring a species of bifidobacteria able to consume the specific milk oligosaccharides delivered by the mother.”[ref]
Non-secretor status plays a role in infectious diseases as well.
Secretor status also plays a role in non-infectious diseases as well, possibly through interactions with the gut microbiome. Non-secretors have a higher risk of:
The rs601338 mutation for non-secretors is not found in Japanese populations, but another SNP codes for non-secretors for Japanese, rs1047781 – T/T genotype.
Several places on the internet mention that bifidobacteria-containing probiotics are good for non-secretors. RenewLife’s Ultimate Flora has a high count of several types of bifidobacteria. VSL #3 is another probiotic that has good reviews and contains bifidobacteria.
If you want to know how many and what type of bifidobacteria are in your gut, you could do a microbiome sample from uBiome or American Gut. Do read their privacy policies thoroughly before buying.