FUT2: Check to See if You Are a Secretor or Non-Secretor

Key takeaways:
~ An FUT2 gene variant controls whether or not you secrete your blood type into your saliva and other bodily fluids, such as your intestinal mucosa. This is referred to as your secretor status for being a ‘secretor’ or ‘non-secretor’.
~ Whether or not you secrete your blood type plays a big role in the type of bacteria in your gut microbiome. It also impacts your susceptibility to the norovirus.
~ Your genetic raw data can tell you whether you are a secretor or non-secretor.
~ Supplements may help with certain aspects of being a non-secretor.

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Non-secretors, the FUT2 gene, and health symptoms:

First, let me explain a little bit of the background science on being a secretor or non-secretor of your blood type, and then I’ll explain how to check your 23andMe or AncestryDNA raw data for your secretor status.

Oligosaccharides and Blood Type:

Your blood type – type A, B, AB, or O – refers to the oligosaccharides that are present on your red blood cells.  Oligosaccharides are carbohydrates consisting of three to nine monosaccharides (simple sugars). You may be familiar with oligosaccharides as prebiotics in supplements or foods like chicory and Jerusalem artichokes.

Your body also makes oligosaccharides, and one of those oligosaccharides is what makes up your ABO blood type. You’re likely familiar with blood types, such as type A positive or type O negative. The A, B, AB, and O refer to the type of oligosaccharide found on your red blood cells and in secretions such as saliva, tears, and the mucosa lining your intestines.

Interestingly, about 20% of people don’t secrete their blood type.  And this creates some fascinating differences.

What is a blood type secretor?

The FUT2 gene encodes the enzyme fucosyltransferase, which controls whether the oligosaccharides that make up your blood type will be expressed in your bodily fluids (other than your blood).

For most people, the oligosaccharides that indicate your blood type are also found in your bodily fluids, including:

• intestinal mucosa
• sweat
• saliva
• tears
• vaginal mucosa
• semen

However, not everyone secretes their blood type in bodily fluids. About 20% of Caucasian and African populations are non-secretors of their blood type.

Why is this important? Being a non-secretor affects how your body interacts with bacteria inside you and impacts your response to certain viruses. Your gut microbiome continually interacts with your immune system, and the species of bacteria present can have an impact on your digestion and also on your immune response.

Let’s dig into some specifics on what is going on with the gut microbiome of non-secretors.

Bifidobacteria, gut microbiome, and secretors:

Researchers consider Bifidobacteria species 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. Your intestinal mucosa is what lines your intestines. It keeps your gut microbiome in the right place and away from your cells.

That’s where secreting your blood type (an oligosaccharide) comes into play.

Secretors tend to have a higher prevalence of the Bifidobacteria good guys in their gut microbiome.[ref][ref]

In fact, some studies show non-secretors have either low or no Bifidobacteria in their gut microbiome. Other studies show that there is decreased Bifidobacteria species diversity in non-secretors.[ref][ref]

Pathogenic bacteria can’t get a grip:

There is one big advantage to being a non-secretor of your blood type — and it is likely that this advantage keeps the non-secretor phenotype so prevalent in the human population.

Certain viruses, such as norovirus, use the blood group glycans to attach to cells and enter them for infection. Without the blood group glycans in the intestinal mucosa, the viruses cannot attach to the intestinal cell walls and enter the body.

Thus, non-secretors are very unlikely to get sick from certain intestinal viruses such as Norovirus and Rotavirus (stomach flu). It is a superpower that likely kept your ancestors from dying from diarrheal disease.[ref][ref]

Non-secretors: Gut microbiome, nutrition, norovirus, B12

So what’s the big deal about being a non-secretor? Well, a lot of it comes back to our body’s interactions with the microbiome.

Non-secretor gut microbiome:

Lack of  Bifidobacteria:
A 2011 study showed that non-secretors had 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 also had a lower diversity of bacteria.[ref]

Another study in 2014 confirmed the findings regarding low bifidobacteria in non-secretor gut microbiomes. Additionally, non-secretors had lower species richness than the secretors.[ref]

Food sensitivities for non-secretors:

Why is the gut microbiome interaction so important? Bifidobacteria are good guys to have in the gut microbiome. They also may play a role in whether you have food sensitivities. Bifidobacteria help with the digestion of gluten, so a wheat or gluten sensitivity in someone who is a non-secretor may be related to the gut microbiome changes.

A plus for non-secretors: resistance to the norovirus!

Non-secretor status plays a role in infectious diseases as well. One big advantage of being a non-secretor is resistance to some viruses which cause what is commonly called the ‘stomach flu’.

• The norovirus and the rotavirus are much, much less likely to infect a non-secretor. Around 99% of non-secretors are protected from getting these infections![ref][ref]
• Infants who are non-secretors are significantly less likely to have symptomatic rotavirus and are less likely (but not completely protected) to be asymptomatic carriers of the rotavirus.[ref]
• Children who are non-secretors are less likely to have diarrheal diseases. Some research indicates that just carrying one copy of the non-secretor allele can reduce the risk of diarrheal diseases in children.[ref]
• H. pylori colonization is lower in non-secretors.[ref] H. pylori is a bacteria that resides in the stomach and can cause ulcers and stomach cancers.

Non-secretors are at an increased risk for certain diseases:

Secretor status also plays a role in non-infectious diseases, possibly through interactions with the gut microbiome. Non-secretors have a higher relative risk of:

• Type 1 diabetes[ref],
• alcohol-induced pancreatitis[ref],
• Crohn’s disease[ref][ref]
• adverse outcomes in premature infants[ref]
• symptoms from E. coli infections[ref]
• slightly higher risk of the mumps[ref]
• increase risk of middle ear infections[ref]

Keep in mind the increase in risk is simply a statistical connection with relative risk. Being a non-secretor does not necessarily mean you will get any chronic disease.

Vitamin B12 levels in non-secretors:

Non-secretors also often have higher serum vitamin B12 levels when they get their levels tested.

Importantly, this may not truly reflect the amount of B12 being transported into the cells. It could be that you have higher serum B12 because it is not getting into the cells. A methylmalonic acid (MMA) test may give you a better indication of your actual vitamin B12 status.[ref]

Breast milk: Oligosaccharides and FUT2 non-secretors

Your microbiome begins to develop at birth. An infant’s microbiome is mostly colonized by its mother, and bifidobacteria usually make up a large part of an infant’s microbiome.

Breast milk contains oligosaccharides that feed the baby’s microbiome. Non-secretor mothers do not produce the 2′-FL oligosaccharide in their breast milk, thus possibly impacting the baby’s microbiome.[ref]

Interestingly, babies born via C-section to non-secretor mothers have altered microbiomes.[ref] Not only did they not get exposure to the vaginal microbiome during birth, but they also aren’t receiving the secretor oligosaccharides from breast milk.

The effects on non-secretor status can also influence breastfed babies of non-secretor mothers, even when not born by C-section.

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]

In other words, if your mom is a non-secretor, your gut microbiome may be altered a little bit.

Related article: Leveraging your gut microbiome to change your gene expression

Lifehacks: Supplements and foods for Non-secretors

If you are a non-secretor, you may want to minimize the ‘downside’ of the altered microbiome while enjoying the fact that you are unlikely to get the norovirus.

Probiotics containing Bifidobacteria:

Graphical Overview:

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