Reviewed and revised on: 02/12/2019
In his book Eat Right 4 Your Type, Dr. D'Adamo first 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 (called FUT2) actually interacts with your blood type gene, and determine your ability to secrete your blood type antigens into body fluids and tissues.
In the genetics of the secretor system two options exist. A person can be either a Secretor or a Non-secretor. 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.
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).
Advantages and Disadvantages:
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 (as you might remember type O's have the highest alkaline phosphatase activity and type A's the least), have lower alkaline phosphatase activity. 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 (vWf) clotting factor 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.
Secretors have the slowest clotting while Non-secretors have shorter bleeding times and a tendency towards higher levels of the clotting 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 atherothrombotic and heart disease.
Disease Susceptibility among Secretors and Non-secretors:
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.
