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.

Microbiome Background, Bifidobacteria

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 and Blood Type:

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.

ABO Blood Group Diagram. Wikimedia Commons - Public Domain.

ABO Blood Group Diagram. Public Domain Image.

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.

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 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):

  •  G/G: FUT2 secretor
  •  A/G:  FUT2 secretor
  •  A/A:  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.  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]

Oligosaccharides in Breast Milk:

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-secretors- Resistance to Infectious Diseases:

Non-secretor status plays a role in infectious diseases as well.

  • The norovirus 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],
  • adverse outcomes in premature infants[ref]


Japanese ancestry:
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.


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:

Genetic Variants and Weight Loss

Microbiome, Genetics and Emulsifiers




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,

Ela · January 29, 2019 at 9:12 am

I’m onlyi ++ for rs 492602 and I have no bifido either. 🙄
Using prebiotics I have baloon in my gut😷

Anne · January 29, 2019 at 5:09 pm

This is a little off-topic but is the FUT2 variant what led the police to Joseph DeAngelo, the suspected Golden State Killer? Newspaper accounts refer to him as being a “non-secretor”.

    Debbie Moon · January 30, 2019 at 12:32 pm

    I’ve read that he was a non-secretor and they couldn’t get his blood type from the semen sample.
    And yes, this FUT2 variant would be the cause of that.
    Thanks for reading and commenting :-)

Ellie · February 24, 2019 at 5:13 pm

I’m a non-secretor! Woohoo! Is this linked to blood type, as my mother and I both have O rh- blood type and neither of us are secretors and neither of us get sick? I can basically lick anything and I never get so much as a mild stomach ache. I have maybe one cold every decade and only then if I’m seriously pushing myself (zero sleep, drink too much, mega stressed, living in damp/freezing conditions week in week out). But even then I don’t get stomach-based sickness. Whereas my brother and sister, who are O rh+ like my father and likely secretors (as he is), all get sick a lot more. My 23&me results say I have slightly increased risk for celiac, but I live on bread and pasta and it doesn’t seem to affect me (unlike my brother).

    Debbie Moon · February 25, 2019 at 3:21 pm

    Hi Ellie –
    Thanks for reading and posting your comment and question!
    No, I don’t think that non-secretor status is tied to blood type in any way. But it is definitely tied to not getting the stomach-based sicknesses :-)

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.) […]

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