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.
Whether you secrete your blood type plays a big role in the type of bacteria that dwell in our 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 – a.k.a. the dreaded stomach flu.
This article digs into the background science of secreting your blood type. Then it explains how to check your genetic raw data. Finally, we will 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 file for this information.
Oligosaccharides and Blood Type:
Oligosaccharides are a carbohydrate that consists 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.
Yep – when you give blood, and they tell you that you have Type A or Type B blood, this means that your body produces a specific oligosaccharide that presents on your red blood cells.
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 express 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 include most people’s blood type are:
- intestinal mucosa
- vaginal mucosa
But… About 20% of Caucasian and African populations are non-secretors of their blood type.
And it turns out that being a non-secretor affects how your body interacts with bacteria inside you and impacts your response to certain viruses.
Bifidobacteria, gut microbiome, and secretors:
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. Your intestinal mucosa is what lines your intestines. It keeps your gut microbiome in the right place and away from your cells.
That is where secreting your blood type (an oligosaccharide) comes into play.
Pathogenic bacteria can’t get a grip:
Additionally, certain viruses, such as the norovirus, use the blood group glycans to attach to cells and enter them for infection. Thus non-secretors are very unlikely to get sick from specific intestinal viruses.[ref][ref]
We’ll come back to this in a minute...first, check your genetic data to see if you are a secretor or a non-secretor.
Check your genetic raw data to see if you are a non-secretor
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.
Check your genetic data for rs1047781 (23andMe v4, v5; AncestryDNA):
- A/A: “secretor” if Japanese or Korean ancestry
- A/T: “secretor” if Japanese or Korean ancestry
- T/T: “non-secretor” if Japanese or Korean ancestry[ref][ref][ref]
Members: Your genotype for rs1047781 is —.
Research on non-secretors:
So what’s the big deal about being a non-secretor? Well, it comes back to our body’s interactions with the microbiome.
Non-secretor microbiomes lack Bifidobacteria:
A 2011 study showed that 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 also have 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 that 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], perhaps a greater risk for Chinese population groups[ref]
- adverse outcomes in premature infants[ref]
- symptoms from e. Coli infections[ref]
- slightly higher risk of the mumps[ref]
Keep in mind that this increase in risk is simply a statistical connection with relative risk. Being a non-secretor does not mean that you will automatically get diabetes or pancreatitis.
B12 Levels in non-secretors:
Non-secretors also often have higher serum B12 levels. It may not truly reflect the amount of B12 being transported into the cells, so a methylmalonic acid test may give you a better indication of your B12 status.[ref]
Oligosaccharides in breast milk:
Your microbiome began to develop at birth. An infant’s 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. 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]
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]
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
COVID-19 and Secretor Status:
A 2021 study found that people with type A blood are at a higher risk of severity with COVID-19 than type O individuals. Several other studies have also made this connection (and blood type matters for disease susceptibility for several other pathogens as well).
This study, though, broke out the type A individuals into secretors vs. non-secretors. The results showed that non-secretors that were type A were not at an increased COVID risk. The type A link to increased severity, according to this study, was just in secretors.[ref] I want to note, though, that this study was rather small and needs to be replicated before putting much weight on it. I’m mentioning the study because it has been passed around on social media that non-secretors may be protected from covid…
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:
Some clinicians recommend 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.
Prebiotics containing 2′-FL (2′-Fucosyllactose):
Mothers who are non-secretors do not produce the 2′-FL oligosaccharide in their breastmilk. This oligosaccharide is now available as a prebiotic via online and other sources. Various strains of bifidobacteria use 2′-FL as a food source, and those bifidobacteria then increase the amount of short-chain fatty acids produced in the gut microbiome.[ref]
Thus combining bifidobacteria probiotics and a 2′-FL prebiotic may be beneficial for increasing short-chain fatty acids in the gut. (I’m making some assumptions here – but it may be worth trying if you are a non-secretor with gut problems…)
Decreasing Gluten Sensitivity with the right probiotic
One theory of why some people are gluten intolerant (without having Celiac) is that low levels of Bifidobacteria and Firmicutes cause alterations to the short-chain fatty acid composition in the gut. It then alters the mucosal barrier in the gut and increases the risk of gluten sensitivity.[ref]
If that theory is correct, then probiotics containing bifidobacteria could help with gluten intolerance.
Related article: Check your celiac genes
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