by Lisa Keilhofer

Blood type as key factor for microbiome composition

In January 2021, a team of scientists from CAU (Christian-Albrechts-Universität zu Kiel) published a study that was able to verify correlations between blood type and microbiome that were unknown until then (1). The human microbiome fortunately moved into the center of scientific attention during the last years and is fairly well-researched today. This makes it even more exciting to find out completely new points from that field of research.

What factors influence our gut microbiome?

Up until today, science has detected a number of factors that have an impact on the composition of our microbiome. Starting with the way a human is born, the basis for the intestinal colonization is set. (see proof-of-concept paper on fecal transplant 2). And, as the platitude goes “you are what you eat”, meaning that our daily intake sets the ground for which microbes are able to dwell and survive within us, and in what scope (all about nutrition and the gut microbiome by the leading experts on that matter, Dr. Rob Knight and Jack Gilbert 3). But also, our local environment shapes the composition of our gut microbiome (4). And the above-mentioned research group from CAU was now able to confirm one further, very important factor on the lists – and it is genetics.

Gene loci influence the composition of our gut microbiome

The publication of the CAU team is based on a study collecting 8,956 stool samples of Germans from fife cohorts in the cities of Kiel, Augsburg and Greifswald. This makes it the biggest genome wide association study (GWAS) in Germany, so far. The study shows a correlation between 38 gene loci (that means, a gene locus is the exact position of a gene on a chromosome) and the colonization of the gut microbiome.

The study by Prof. Dr. Andre Franke found a correlation between the genes that are responsible for the ABO blood type and the microbial composition of the gut. The blood types A, B and AB emit blood type antigens to the gut as “secretors”. Those show to particularly encourage the growth of one bacterial genus. Mainly sugar residues appear to deliver energy to the bacteroides located in the gut and foster their prevalence (see also 5).

First author of the study, Dr. Malte Rühlemann, explains: “Previous studies show that people without this secretion way can cope better with norovirus infections, for instance”. Also, Co-author Prof. John Baines, has been researching on that forms of metabolism for quite some time and is happy to add a milestone to this research with these outcomes.

More mild courses of Covid-19 with blood type 0

With those results, the authors also add information to the research on the new corona virus (6). A genome wide association study scrutinized 1980 severe courses of Covid-19 infections with patients in seven hospitals in Italy and Spain. The evaluation showed that patients of blood type A suffered from more severe courses compared to the other patients. The mildest courses were reported for blood type 0.

The study was funded by the German Ministry of Education and Research to gain insights into the new coronavirus. The homepage of the ministry sums up the results (7), pointing out the gene locus on the third chromosome to be crucial. It is the same segment that the GWAS on norovirus identified as key factor.

Risk patient because of blood type?

What do we do with those results? Are you less capable to cope with virus attacks with blood type A, B or AB? Several studies show a correlation between blood type and severity of viral infection; however, this is not the only factor influencing your health.

At the same time, the results open a door to an exciting causality: Besides nutrition and external factors like the way of birth, one further key factor appears to be dominating the composition and functionality of our gut microbiome: genetics. This research again shows how complex the interaction of our body and our microbiome is. We can very well assume that there are further genetic factors that manifest in our bodies through the presence or absence of certain metabolic products. And those form the basis for certain microbes – or lack it.

Sources / References:

(1) Rühlemann M, Hermes B, Bang C et al. Genome-wide association study in 8,956 German individuals identifies influence of ABO histo-blood groups on gut microbiome. Nat Genet (2021).

(2) Korpela K, Helve O, KolhoK-L, Salonen A, Andersson S, de Vos W. Maternal Fecal Microbiota Transplantation in Cesarean-Born Infants Rapidly Restores Normal Gut Microbial Development: A Proof-of-Concept Study. Cell (2020). Maternal Fecal Microbiota Transplantation in Cesarean-Born Infants Rapidly Restores Normal Gut Microbial Development: A Proof-of-Concept Study (

(3) Gilbert J, Knight R. Dirt is Good (2007). Review unter Dreck macht Speck? Überzogene Hygienemaßnahmen und das Immunsystem. - MyMicrobiome

(4) Vangay P, Johnson AJ, Ward TL, Kashyap PC, Culhane-Pera KA, Knights D. US Immigration Westernizes the Human Gut Microbiome. Cell (2018). US Immigration Westernizes the Human Gut Microbiome (

(5) Darmmikrobiom: Einfluss der Blutgruppe - DocCheck.

(6) Franke A, et al. Genomewide Association Study of Severe Covid-19 with Respiratory Failure, N Engl J Med (2020),

(7) BMBF, Covid-19: Schwerer Verlauf durch Blutgruppe beeinflusst? (2020),

Lisa Keilhofer
Lisa Keilhofer

Lisa Keilhofer studied at the University of Regensburg. She works in internationalization and as a freelance editor.

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