I am constantly amazed at the interaction between our bodies and the microbes within us. Yes, a bit geeky, but this stuff is really cool!

Whether or not you secrete your blood type plays a big role in the type of bacteria that dwell in our gut microbiome and whether you are likely to get sick from the norovirus.  

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.

Microbiome Background, Bifidobacteria

Bifidobacteria are thought to be one of the good guys when it comes to your gut microbiome. They are lactic acid and acetic acid producing bacteria, and they help your immune system keep everything in check.  These bacteria are involved in breaking down carbohydrates (specifically, oligosaccharides) from the foods you eat, and they also eat oligosaccharides produced by our body in the intestinal mucosa. That is where secreting your blood type (an oligosaccharide) comes into play.[ref][ref]

Oligosaccharides and Blood Type:

Oligosaccharides are a carbohydrate that consists of three to nine monosaccharides (simple sugars). There are three types of oligosaccharides that are in the news these days as helpful prebiotics: fructooligosaccharides (FOS), galactooligosaccharides (GOS), and inulin. You can get oligosaccharides as pre-biotic supplements and they are also found in foods like leeks, Jerusalem artichokes, onions, chicory root, and oats.

ABO Blood Group Diagram. Wikimedia Commons - Public Domain.

ABO Blood Group Diagram. Public Domain Image.

The FUT2 gene encodes the enzyme fucosyltransferase, which plays a role in forming oligosaccharides.

Most people are familiar with the ABO blood type system and probably 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.

FUT2 Genetic Variants

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 thought to be non-secretors. A FUT2 non-secretor has a homozygous mutation in the SNP rs601338 that changes G to A. Those with AG or GG (heterozygous and wild-type) are FUT2 secretors.

Check your 23andMe results for rs601338 (v4, v5):

  •  GG: FUT2 secretor
  •  AG:  FUT2 secretor
  •  AA:  FUT2 non-secretor, lower amounts of bifidobacteria, resistant to norovirus

Effects of Being a Non-Secretor:

So what is the big deal about being a non-secretor?  Well, it comes back to our bodies interactions with the microbiome.  In a 2011 study, individuals with the AA allele on rs601338 (non-secretors) were shown to have significantly lower amounts of bifidobacteria in their gut microbiome. This makes sense when you think about bifidobacteria being fed, in part, by our intestinal mucosa.   Interestingly, the same study showed that non-secretors actually had a higher diversity of bacteria.  Another study in 2014 confirms those findings.

Oligosaccharides in Breast Milk:

An infants microbiome is, in part, colonized from the mother, and bifidobacteria usually make up a large portion 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-secretors- Resistance to Infectious Diseases:

Non-secretor status plays a role in infectious diseases as well.  Both the norovirus (famous for spreading rapidly on cruise ships and through nursing homes) and the rotavirus are much less likely to infect a non-secretor.[ref][ref]  Children who are non-secretors are less likely to have diarrheal diseases.[ref]  H. pylori colonization is also less in non-secretors.[ref]

Non-secretors- Increased Risk for Some Diseases:

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 Type 1 diabetes[ref], alcohol-induced pancreatitis[ref], Crohn’s disease[ref], and adverse outcomes in premature infants[ref].

This is one genetic mutation that is dependent on ancestry and applies mainly to Caucasians. The rs601338 mutation for non-secretors is not found in Japanese populations, but another SNP codes for non-secretors for Japanese, rs1047781 – TT genotype.


Probiotics containing bifidobacteria:

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.

Microbiome sequencing:

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.

More to read:


Lisa Stephenson · December 14, 2018 at 6:15 pm

Is it only rs 601338? I am ++ for rs492602 and rs602662 and I have no bifidobacterium and gut issues.

    Debbie Moon · December 17, 2018 at 6:53 pm

    Hi Lisa,
    All three of those SNPs are inherited together for almost everyone. So if you have the risk alleles for rs492602 and rs602662, then you almost certainly also have the risk alleles for rs601338 and be a non-secretor.
    Thanks for commenting,

Genetic Lifehacks | More on the genetics of celiac disease… · September 2, 2015 at 4:30 pm

[…] A Finish study from 2012 found that FUT2 non-secretors are at an increased risk of celiac disease.  The AA genotype for rs601338 determines a non-secretor.  The odds ratio for non-secretors for celiac is 1.28.  (Non-secretors are also resistant to the Norovirus.) […]

Genetic Lifehacks | Weight Loss Genetics – Obesity Virus? · October 23, 2015 at 1:25 pm

[…]  We know that some people are genetically protected from certain viruses such as the Norovirus.  (Gut Health and Your Genes)  HIV, herpes, and other viruses are attenuated by genetic polymorphisms. Could there be a genetic […]

Genetics of Celiac Disease · April 22, 2016 at 12:12 pm

[…] A Finish study from 2012 found that FUT2 non-secretors are at an increased risk of celiac disease.  The AA genotype for rs601338 determines a non-secretor.  The odds ratio for non-secretors for celiac is 1.28.  (Non-secretors are also resistant to the Norovirus.) […]

Leave a Reply

Your email address will not be published. Required fields are marked *

Related Posts

Disease Prevention

Factor V Leiden

Say you are chopping up peppers for your morning omelet and slip with the knife. Ouch! While cutting your finger seems to produce a huge amount of blood compared to the size of the wound, the Read more…

Disease Prevention

Will vitamin E increase or decrease your risk of cancer?

I often think that if a little bit of something is good for you, more should be even better…  But that is often not the case when it comes to health.  arge, population-wide studies of Read more…

Disease Prevention

Genetic Variants Associated with PCOS

Polycystic ovarian syndrome (PCOS) is an endocrine disorder that causes an increase in androgen hormone production in women. It affects 5 -10% of premenopausal women, and genetics plays a large role in whether you have PCOS. Read more…