A genetic variant in the FUT2 gene 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’.
Why is this important? Whether or not you secrete your blood type plays a big role in the type of bacteria in your gut microbiome. Being a non-secretor can have both positive and negative impacts. For example, being a non secretor protects you from getting the norovirus, but can also lead to intestinal issues.
This article digs into the background science of secreting your blood type. Then it explains how to check your genetic raw data. Finally, we wrap up with ‘lifehacks’ for dealing with being a non-secretor.
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 a carbohydrate 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.
These bodily fluids that usually include your blood type are:
- intestinal mucosa
- vaginal mucosa
But… About 20% of Caucasian and African populations are non-secretors of their blood type.
Plus, it turns out that being a non-secretor affects how your body interacts with bacteria inside you and impacts your response to certain viruses. Your gut microbiome impacts your immune system on an ongoing basis, 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 which 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 very low or no Bifidobacteria in their gut microbiome.
Pathogenic bacteria can’t get a grip:
There is an advantage to being a non-secretor of your blood type — and it is likely this advantage which keeps the non-secretor phenotype so prevalent in the population.
Certain viruses, such as the 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]
Before we go any deeper into the research, check your 23 and Me or AncestryDNA raw data to see if you are a non-secretor or a secretor.
FUT2/Secretor Genotype Report
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Membership lets you see your data right in each article and also gives you access to the members’ only information in the Lifehacks sections.
FUT2 Gene: codes for fucosyltransferase enzyme
Check your genetic data for rs601338 (23andMe v4, v5; AncestryDNA (some)):
- G/G: blood type secretor
- A/G: blood type secretor
- A/A: non-secretor of blood type, lower amounts of bifidobacteria, resistance to norovirus
Members: Your genotype for rs601338 is —.
East Asian ancestry:
The SNP to check for secretor vs. non-secretor is different if you are of East Asian ancestry.
Research on non-secretors:
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 microbiomes lack 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 non-secretors also had a lower diversity of bacteria.[ref] Another study in 2014 confirmed those findings.[ref]
The good side of being a non-secretor: 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]
- 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 also less in non-secretors.[ref] H. pylori bacteria 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]
Keep in mind the increase in risk is simply a statistical connection with relative risk. Being a non-secretor does not mean you will automatically get diabetes or pancreatitis!
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, so 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 began to develop at birth. An infant’s microbiome is mostly colonized from their 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 breastmilk, 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 the 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 for non-secretors:
If you are a non-secretor, you may want to minimize the ‘downside’ while enjoying the fact that you are unlikely to get the norovirus.
Probiotics containing bifidobacteria:
The rest of this article, including the information on the connection to gluten sensitivity, is for Genetic Lifehacks members only. Consider joining today to see the rest of this article.
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Debbie Moon is the founder of Genetic Lifehacks. Fascinated by the connections between genes, diet, and health, her goal is to help you understand how to apply genetics to your diet and lifestyle decisions. Debbie has a BS in engineering and also an MSc in biological sciences from Clemson University. Debbie combines an engineering mindset with a biological systems approach to help you understand how genetic differences impact your optimal health.