What is a Secretor?

What is a Secretor?


Knowing your blood group and subgroups is one way to discover specific information about your body’s genetic makeup and susceptibility to disease. This fact sheet is for educational purposes only. For those suffering from a specific condition it is recommended that you get assistance from a healthcare provider. Some practitioners familiar with the significance of blood groups are listed on the internet in the Eat Right 4 Your Type practitioner registry.


Secretors and Non-secretors

An overview and preview of the new saliva-based secretor test

Introduction In the book Eat Right 4 Your Type, Dr. D’Adamo introduced readers to the concept of Secretors/Non-secretors. By now you are familiar with the concept that your ABO blood type is controlled by your genetics. The gene coding for your blood type lies on chromosome 9q34. However, a separate gene actually interacts with your blood type gene, determining your ability to secrete your blood type antigens into body fluids and secretions.

In the genetics of the secretor system two options exist. A person can be either a Secretor (Se) or a Non-secretor (se). This is completely independent of whether you are a blood type A, B, AB, or O. This means that someone can be an A Secretor or an A Non-secretor, a B Secretor, or a B Non-secretor etc.

In a simplified sense, a Secretor is defined as a person who secretes their blood type antigens into body fluids and secretions like the saliva in your mouth, the mucus in your digestive tract and respiratory cavities, etc. Basically what this means is that a secretor puts their blood type into these body fluids. A Non-secretor on the other hand puts little to none of their blood type into these same fluids. As a general rule, in the U.S. about 20% of the population are Non-secretors (with the remaining 80% being Secretors).

The Secretor Edge

With respect to the ABO blood types, it is very difficult to state that one type is more advantageous than another. Each blood type has its own strengths and characteristic weaknesses. However, this does not appear to be the case with the Secretor gene. As a generality, being a Non-secretor (based on all of the available information) does actually appear to be a potential health disadvantage. At a very basic level, being able to secrete blood type into your saliva, mucus, etc. allows for an added degree of protection against the environment, particularly with respect to microorganisms and lectins.

An additional advantage of being a Secretor might be a generalized tendency to promote a stabilized, blood-type friendly intestinal bacterial ecosystem. Many of the friendly (probiotic) bacteria in your digestive system actually use your blood type as one of their preferential foods. Since Secretors have a steady supply of blood type in the mucus that lines the digestive tract, their bacteria have a much more constant food supply.

Metabolic Differences Between Secretors and Non-Secretors

Similar to the ABO blood types, it appears additional genetic information must be linked to the Secretor gene, because predictable trends in non-blood type aspects of physiology have a close association with Secretor/Non-secretor status. Aspects of physiology such as the relative activity of an enzyme called intestinal alkaline phosphatase; propensities toward clotting, reliability of some tumor markers, and generalized performance of your immune system have predictable trends depending upon your Secretor status.

The activity of intestinal and serum alkaline phosphatase is strongly correlated with secretor phenotypes. Basically, Non-secretors, independent of their ABO blood groups, have lower alkaline phosphatase activity (as you might remember type O’s have the highest alkaline phosphatase activity and type A’s the least). It has been estimated that the serum alkaline phosphatase activity of Non-secretors is only about 20% of the active in the secretor groups.

As was mentioned in Eat Right 4 Your Type, blood type impacts the clotting ability to a significant degree. In fact, it has been estimated that a significant fraction (30%) of the genetically determined variance in plasma concentration of the von Willebrand factor antigen (vWf) is directly related to ABO blood type. As a rule, it is blood group O individuals who have the lowest amount of this clotting factor and the tendency for the lowest degree of clotting/platelet aggregation.

In the Secretor/Non-secretor world, Secretors have the slowest clotting while Non-secretors have shorter bleeding times and a tendency towards higher factor VIII and vWf. ABO and Secretor genetics actually further interact to influence blood viscosity. In essence what this means is that an A Non-secretor will be at the far end of the spectrum with the slowest bleeding times, thickest blood viscosity, and the most probability to have high platelet aggregation. On the other end on the continuum will be O Secretors, who will have the longest bleeding time, thinnest blood, and least tendency for platelet aggregation. Because of this, Non-secretors (especially the type A’s) tend to be at the highest risk for future atherothromboti and heart disease.

Disease Susceptibility among Secretors and Non-secretors:

Digestive System
As a general rule, a higher intensity of oral disease is found among Non-secretors. This includes dysplasia (precancerous changes to the tissue) and an increase in cavities. Statistically speaking, blood type A Secretors have the lowest number of cavities. Non-secretors also tend to have more digestive problems. Several studies have indicated that Non-secretors have a significantly higher rate of duodenal and peptic ulcers. Non-secretors are also less resistant to infection by Helicobacter pylori (a microbe associated with ulcers). It appears that this organism can colonize more readily and generate more inflammation in individual’s incapable of secreting their blood type into the digestive tract. Non-secretors are at an increased risk for development of celiac disease (up to 48% of patients with celiac disease have been reported to be Non-secretors).

Respiratory System
With regards to aspects of lung function, being a Non-secretor takes its usual place as a health disadvantage. Several researchers have suggested that being a Non-secretor might predispose an individual to damaging effects, while being a secretor might add a degree of protection against harmful environmental assaults to our lungs.

Among coal miners, asthma was significantly related to Non-secretor phenotype. Secretors also appear to receive a degree of protection against some of the deleterious effects of cigarette smoking. Evidence suggests that the ability to secrete ABO blood type antigens might decrease the risk of Chronic Obstructive Pulmonary Disease (COPD). Being a Non-secretor also offers a slight increase risk for having a problem with habitual snoring.

Autoimmune Disease
Non-secretors appear to have an increase in the prevalence of a variety of autoimmune diseases including ankylosing spondylitis, reactive arthritis, psoriatic arthropathy, Sjogren’s syndrome, multiple sclerosis, and Grave’s disease.

Diabetes, Heart Disease, & Metabolic Syndrome X
Non-secretors are at a greater risk of developing diabetes (especially adult onset diabetes); and they might be at a greater risk of developing complications from diabetes. Data allows the conclusion that Non-secretors are a risk factor for myocardial infarction and heart disease (note: this is particularly true for men).

Several different researchers have noted a connection between a metabolic syndrome called “Syndrome X” and Non-secretor blood types. Syndrome X is a clustering of metabolic problems comprised of insulin resistance (your cells do not respond effectively to the insulin that you create), elevated plasma glucose (high blood sugar), lipid regulation problems (elevated triglycerides, increased small low-density lipoproteins, and decreased high-density lipoproteins), high blood pressure, a prothrombic state (tendency to clotting), and obesity (especially central obesity or a predisposition to gaining weight in the abdomen).

This cluster of metabolic disorders seem to interact to promote the development of diabetes (adult onset type II), atherosclerosis, and cardiovascular disease. And while insulin resistance might lie at the heart of the problem, all of these metabolic disorders appear to contribute to health problems.

Alcoholism has been associated with the Non-secretor blood type. On the positive side, alcohol consumption appears to exert a protective effect on lung function and to lower the risk of heart disease more in Non-secretors than in Secretors. The key principle with the use of alcohol is for Non-secretors (and everybody actually) is moderation.

Bacteria Urinary Tract Infections
Non-secretors are at a greater risk for recurrent UTI’s, have a greater tendency to increased inflammation, and are much more likely to develop renal scars. Being a blood type Secretor on the other hand offers a degree of protection; cutting your risk of recurrent UTI’s by greater than 50% and dramatically decreasing the likelihood you will have renal scars develop.

Candida infection
Based upon this tendency of Non-secretor saliva to not only fail to prevent attachment of Candida, but maybe actually promote the binding of Candida to your tissue, we would expect that research would show higher tendency to Candida problems among Non-secretors. This is what we find to be true. Non-secretors are much more likely to be carriers of Candida and to have problems with persistent infections. Blood type O Non-secretors might be the most affected of the Non-secretor blood types, since Candida also appears to have an easier time colonizing (attaching to) the blood type O antigen.

Antibody levels
Secretors are known to have higher levels of IgG and IgA antibodies. The lack of IgA antibodies perhaps explains the link between non-secretor status and an increased frequency of heart valve problems secondary to bacteria infection. Because IgA functions much like the way a rampart or palisade wall protects a town from invasion, most if not all non-secretors have problems with gut permiability (“leakygut”).

Further Information


Lewis Blood Group and Secretor Status: [Gene location: 19q13.3] The molecule that defines your blood group is called an antigen. People of each blood group have that specific antigen on their red blood cells: A has the A antigen, B has the B antigen AB has both A and B antigens and O has the H antigen. The term “ABH secretor” refers to secretion of ABO blood group antigens in fluids such as saliva, sweat, tears, semen and breast milk. If you are an “ABH secretor”, you will secrete antigens according to your blood group. For example, group O people will secrete H antigen, group A will secrete A and H antigens, etc. Approximately 80% of people are ABH secretors. There are several differences between ABH secretors and non-secretors, especially relating to function of the immune system. There are altered dietary requirements, which are outlined in LR4YT and The Complete Blood Group Encyclopedia.

Lewis blood group is a minor blood group that relates to salivary secretor status. Salivary ABH secretor determination is based on testing for your blood group antibodies in your saliva. Finding your Lewis blood group (Lea and Leb) will tell your ABH secretor status in most cases, irrespective of your blood group. Most ABH secretors have a Lewis group of: Lea- Leb+. Most ABH non-secretors have a Lewis group of: Lea+ Leb-. A small minority (about 5% of the population) will be Lewis Double Negative (LDN): Lea- Leb-. For LDN people Lewis blood group cannot be used to determine ABH secretor status. ABH Saliva testing is available for this purpose. LDN people share most of the same metabolic consequences as ABH non-secretors, and in a few instances they have the most severe manifestations. According to Dr. D’Adamo “It may be helpful to think of LDN individuals as a special category of non-secretor”.

Although ABH salivary secretor status is often thought of as an ‘all or none’ situation, this is not always the case. Some people known as ‘partial’ or ‘weak secretors’ have a greatly reduced quantity of active A or B blood group substance in their saliva, predisposing them to similar functional problems as non-secretors. In the same way, Lewis antigens can also give a ‘weak’ result. Where relevant, weak Lewis results will be reported, as will Lea+ Leb+ (a rare temporary situation, brought about by circumstances such as pregnancy).