|MadSci Network: Genetics|
Kevin, I'll provide the *direct* answer to your question in a moment. I did look at www.dadamo.com website and from there I went to the definitive place to look - PubMed, part of the NIH's website at http://www.ncbi.nlm.nih.gov/PubM ed/ I did find references from over ten years ago that "non-secretors" had a somewhat higher risk of autoimmune diseases, for reasons unknown then and still unknown. And a 1989 review article mentioned that this was controversial so hardly to be considered well-proven. Since nothing has been published since 1989 on the subject I think it proved untrue. I found nothing indicating that type As or type Os lean any particular way in their diets. I did find one reference asking if this so called "blood type diet" is fact or fantasy - but the article was in Norweigian so I was out of luck. I'm not saying it isn't factual, but there doesn't seem to be any evidence in the medical literature supporting it. If D'Adamo has such evidence then it should be published with peer review to insure the accuracy of the data. But I have my suspicions - most "diet gurus" are scam artists out to make a buck. Given the lack of publications in the medical literature since 1989, the assertion that "non-secretors" don't live a full life or have weakened immune systems I believe is nothing but something contrived to sell books. But, let's suppose for a moment that there is genetic linkage between blood type and secretion of alkaline phosphatase. That isn't to say that blood type controls the secretion, it means that the two genes are very close to one another on your chromosomes. Genes linked on the same chromosome (remember, you have 22 paired chromomsomes plus 2 sex chromosomes) are often linked and the closer together on the chromosome the tighter the linkage. Through very poorly understood mechanisms, though, chromosomes can break and rejoin with the other chromosome that makes up the pair - leading to new gene arrangements. Again, the possibility that bloodtype and alkaline phosphatase secretion could be 'separated' would depend greatly on the distance between the two genes. So it would be better to screen for the gene controlling secretion of alkaline phosphatase rather than blood type. Another thing to keep in mind is that your digestive system changes drastically from birth up until you become a full-fledged adult. This is why your taste buds change over time - things that didn't taste good as a kid taste good as an adult - this is a reflection of changes in your body's needs, the body trying to guide you in what to eat. So I see no value in evaluating fetal blood type to aid digestion. If true you could easily screen after birth and then evaluate diet as the child matures. And finally - your question is a little vague. Are you asking whether we should use genetic engineering to fix the non-secretory phenotype, assuming that it is a problem? That technically could be done but raises huge moral issues. There are diseases of genetic origin that we could screen for and possibly could cure by genetic engineering. But this science is in it's infancy - not something I would trust my child's life with no matter how severe the potential disease. And, if the science were to be perfected - why stop there? Why not engineer genes that control obesity or cholesterol, or genes that control addiction to narcotics? Certainly genes associated with cancer or autoimmune diseases would also be high on the list. Where would we stop? Once we've done all that, why not let the person choose the gender, the eye color, the hair color, the height, etc...? Here's the rip - those genes exist for a reason, and that reason is that it confers some evolutionary advantage even if we can't necessarily see it. For example, the gene that causes sickle cell anemia in Africans. When a child gets both copies of that gene the resulting illness is deadly. So why did this gene arise, and why is it still in the gene pool? Simple - scientists found that people with one copy of the gene were resistant to infection by malaria. So they were less likely to die from malaria but there was a one in four chance that one of their children would have sickle cell anemia. Again - the moral issue is the bugger and how you answer it probably depends greatly on whether you are someone who suffers from, or knows someone who suffers from, a debilitating disease with a genetic cause. But keep in mind that tampering with our genes is tampering with nature and the consequences could be dire for our species.
Try the links in the MadSci Library for more information on Genetics.