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Chapter One

The Unmistakable You

The Blood Type Gene

What makes me me, and you you? This is the question that is at the heart of the genetic puzzle. It is also central to our exploration of blood types. What is the animating principle that determines the unique set of characteristics you possess, and the different set that belongs to me?

    The key is genetic heritage. Your genetic heritage is the unbroken story line of your life. Even though you are living in the twenty-first century, you share a common bond with your ancestors. The genetic 'information' that resulted in their particular characteristics has been passed on to you.

    A helpful analogy is the way a computer manages information. Think of the very process of writing this book. As I sit at my computer, only my creative powers and my typing skills limit me. I am free to move words, sentences, or even whole paragraphs around. This information lies in the dynamic portion of my computer, called the RAM (random access memory). Should a sudden power outage occur, or I neglect to save the material to the hard drive, it would all be lost. However, if I am satisfied with this writing, it will be permanently saved to the hard drive, available for use at a later time.

    Your genetic heritage is your biologic hard drive. Embedded within it are the recordings of past 'writings' that were saved for later use-along with, in some cases, a few 'disk errors.' These recordings are stored in your DNA (deoxyribonucleic acid). One of the 'saved' pieces of information is your blood type.

    What determines your blood type? In genetic lingo, the blood type variations are known as alleles. Every person contains alleles-alternate forms of genes. The alleles determine whether you have blue eyes or brown, are tall or short, have black hair or red, and other distinctions. There are three blood type alleles-A, B, and O. That means there are three variations, or alternatives, for your blood type. However, the influence of your blood type is far greater than that of the gene that gives you eye color. Much of that influence has to do with its location and the way it interacts with other genes.

On the Street Where Blood Type Lives

The gene for ABO blood type is located on the q leg of chromosome number 9, around band 34. So the address for your blood type gene is 9q34. It is here that the three basic alleles of the ABO blood system are found, leaving you a Type O, A, B, or AB. The mechanics of blood type's influence have to do with the way genes influence other, seemingly unrelated, genes located immediately adjacent or nearby. This mechanism explains why your blood type can have an impact on such a diverse number of bodily systems-from digestive enzymes to neurochemicals.

    We already know of some intimate relationships between the blood type gene and other genes that impact on our health and well-being. For example, in 1984, researchers reporting in the journal Genetic Epidemiology presented evidence of a family pedigree in which a major gene for breast cancer susceptibility is located near band q34 on chromosome 9. There is a clear genetic connection between blood type and breast cancer.

    Many nutrition experts are baffled when they first hear about the link between blood type and digestion. That's because they are only considering the physical significance of blood type as a surface antigen. Actually, it is not your blood type antigen that is influencing the level of acid in your stomach, but rather the gene for your blood type influencing other seemingly unrelated genes located immediately adjacent (or very close ) to the ABO blood type gene that can exert an effect on your stomach acid levels. This phenomenon, called gene linkage, isn't well understood yet, but it is well known: Many genes influence the actions of other, seemingly unrelated genes.

    Here's another intriguing link that suggests a relationship between blood type and the brain. The gene for the enzyme dopamine beta hydroxylase (DBH), which converts dopamine to noradrenaline, is located right at 9q34. It's literally sitting on top of the gene for blood type. As we will see later, this has vast implications for the association between blood type and stress, mental health, and even personality characteristics.

Your Subtypography

Although there are four blood types-O, A, B, and AB-it would be a ridiculous simplification to suggest that there are only four types of people in the world. The reality is far more intricate and complex. Now, let's take it to another level. Subtyping your blood type, especially your secretor status, provides an even greater specificity of identification. Your blood type doesn't just sit inert in your body. It is expressed in countless ways-and the ways in which it is expressed make a difference. A simple analogy would be a water faucet. Depending on the water pressure, the faucet might pour or dribble. You have access to a lot of water or a little water. In the same way, your secretor status relates to how much and where your blood type antigen is expressed in your body.

Secretor: 9q34's First Cousin

Across town from 9q34, on chromosomes 11 and 19, reside the blood type gene's very important first cousins, the blood type secretor genes. Although your secretor gene is independent of your blood type, it influences the way your blood type is expressed. Everyone carries a blood type antigen on their blood cells, but most people (between 80 and 85 percent of the population) have blood type antigens that float around freely in their body secretions. These people are called secretors, because they 'secrete' their blood type antigens into their body fluids, such as saliva, mucus, and sperm. If you're a secretor, you can learn your blood type from these other body fluids, as well as from your blood. People who do not secrete their blood type antigens in other fluids besides blood are called, reasonably enough, non-secretors.

    Because secretors have more places to put their blood type antigens, they have more blood type expression in their bodies than non-secretors. Your secretor status can have a great influence on the characteristics of your immune system and is associated with a wide variety of diseases and metabolic conditions.

Determining Your Secretor Status

There is a 'quick and dirty' method of estimating secretor status. This involves looking at an additional minor blood typing system, called the Lewis Blood Grouping System, which is functionally interlocked with secretor genetics, since the same gene codes for both the secretor type and the Lewis System. In the Lewis System, located on chromosome 19, there are two possible antigens that can be produced, called Lewisa and Lewisb. (The a and b antigens of the Lewis System should not be confused with the A and B of the ABO system.) People can type out as one of three varieties: Lewisa+ b-, Lewisa-b+, and Lewisa-b-. (A fourth variation, Lewisa+b+, is extremely rare.) The Lewis System can determine secretor status because it has been noted that people who type out Lewisa+b- are also non-secretors, while those who type out as Lewisa-b+ are also secretors. The connection between secretor status and the Lewis System occurs because secretors convert all of their Lewisa antigen into the Lewisb form (making them Lewisb+), while non-secretors do not (leaving them Lewisa+). The reason I say that this test is quick and dirty is that there are some leftovers that can't be typed this way. People who are Lewisa-b- cannot use this test for determining secretor status. Because they have no ability to produce Lewis substances to start with, they never have +a or +b characteristics on their blood or in their secretions. These individuals can either be secretors or non-secretors of blood type substances, but they will always be non-secretors of Lewis substances. In many instances, Lewis negative individuals have unique interactions with diseases, microbes, or metabolic syndromes. Typically, when I've used the Lewis System to determine secretor status, I've lumped Lewis negative patients and Lewisa+ patients into the category of non-secretors. Fortunately, only 6 percent of the Caucasian population and 16 percent of the black population are Lewisa-b- , allowing the greater majority of people to be secretor tested from the same blood samle that we use to test blood type.

Why Secretor Status Matters

We don't yet know precisely why nature made some of us secretors and some of us non-secretors, but we can surmise that secretor status is related to nature's effort to provide some additional layer of protection that didn't exist for the earliest humans. There is some evidence that the non-secretor state is genetically older than the secretor state and may have been more compatible with the digestive needs of hunter-gatherers.

    The secretor state was most likely an immunologic adaptation. When you are able to secrete your blood type antigens into saliva, digestive secretions, and other fluids, these secretions appear to create a barrier against environmental elements, such as bacteria, pollutants, and other irritants. Immunologically, non-secretors seem to have more of a 'death trap' strategy: They allow pathogenic invaders a way in, and then attack and kill them internally.

    These are some of the areas controlled or influenced by your secretor status:

* the degree to which foreign bacteria invade the system

* the adherence of lectins and other blood type

* sensitive structures in food to your digestive tissue

* syndrome X or Insulin Resistance Syndrome

* the balance of intestinal bacteria

* predicting the relevance of tumor markers for diagnosing cancer

* blood-clotting capabilities

* the makeup of a mother's breast milk

* susceptibility to Candida-type infections

* immune resistance

* susceptibility to dental cavities

* sensitivity to the bacteria that causes ulcers

* relative risk for the development of inflammatory bowel problems

* an influence in respiratory heath and susceptibility to viruses

* prevalence of autoimmune diseases

* risk factors for cardiovascular disease

* a genetic predictor of alcoholism

Here's an example of a practical ramification of your secretor status. Let's say you are a Type O about to undergo a surgical procedure. Type O has the lowest concentration of blood-clotting factor, so is more susceptible to bleeding problems. Secretors also have a very low amount of clotting factor. Therefore, if you are a Type O secretor, you have a higher risk of uncontrolled bleeding than if you were a Type O non-secretor.

Here's another example, which has special relevance to Blood Type A. Experience has shown that about 10 percent of the people following the Type A Diet from Eat Right 4 Your Type find that they have some problems with the relatively high level of carbohydrates advocated for Type A. Most of these Type A 'non- responders' are female. Since ER4YT only dealt with A, AB, B, and O types, the diets had to play the odds and assume that the average reader was a secretor, by far the more numerous subtype. No special allowances were made for non- secretors. I've found that, by and large, these non-responders are Type A non- secretors, and their problems are caused by insulin resistance, which often occurs in this subtype. Type A non-secretors may need to increase the percentage of protein in their diets (using such foods as ocean fish and poultry) and downplay the simple carbohydrates. With this in mind, we've adapted the basic Blood Type Diets to reflect secretor-based variations.

The Journey Continues

We are accustomed to picturing the course of human evolution as a straight line, with markers along the way that identify significant shifts. In Eat Right 4 Your Type, blood type evolution was described in a purposely linear manner, in an effort to communicate the basic idea. However, we know that the evolutionary process is more loop than line, more circular than linear. When we talk of Type O being first, Type A second, followed by Type B, then Type AB, we're not describing a seamless march from hunter to farmer to nomad and beyond. Evolution occurs on an invisible landscape, the actual process spanning eons. The refinements in our species and the many subspecies are the hammer of environmental demands arriving with the force of small taps rather than with thundering blows. These refinements have but one purpose-our survival. Today, as we arrive at a new century, we have the understanding and the tools to maximize our capacity for survival, using the genetic material that nature has supplied.

Copyright © 2000 Dr. Peter J.D'Adamo. All rights reserved.