LEWIS BLOOD GROUP TEST
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).
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.
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