The Zone and blood types
Last Updated Aug 2007
The Zone and blood types
By: Dr. Barry Sears
One of the more interesting topics in Zone Central is the hypothesis put forward in Dr. Peter D’Adamo’s recent book on whether or not one’s blood group determines what diet they should eat. The basic hypothesis of the book is in accord with the Zone because genetic diversity accounts for many of the differences in insulin response to the same given amount of carbohydrates.
Although I have serious reservations about some parts of Dr. D’Adamo’s theories (such as lectins from plant sources reaching the bloodstream and then affecting target tissues), the fact that genetic diversity may predict what is the appropriate protein to carbohydrate ratio for a person is an exciting possibility.
To test this hypothesis, we recently determined the blood types of more than 300 individuals as part of our ongoing San Antonio study on Type II diabetics. Approximately 100 individuals were Type II diabetics, whereas the other 200 served as controls. If there was a significant effect of blood types on the likelihood of developing Type II diabetes (a disease characterized by an oversecreation of insulin), then very significant differences in the two populations of blood types should appear.
While there were differences, they were not as great as one would like to expect. As expected from Dr. D’Adamo’s hypothesis, Type O blood had a slighter higher representation in the Type II diabetic group than the normals. But then so did Type A, which is supposed to represent a population more attuned to eating a high-carbohydrate diet. On the other hand, Type AB and Type B had a lower representation in the Type II diabetic group than in the general population.
Does this pilot study (which will be presented at the annual Barnes research conference on endocrinology in October) mean that blood group types have no diagnostic predictive value? No, it only means that further testing is required to really determine the potential of this hypothesis in predicting the most favorable dietary choices. (Boy, does that sound like the typical weasel words research scientists love to use. But sometimes it’s hard to break old habits).
The key to the Zone is flexibility. Try experimenting with different ratios of protein-to-carbohydrate and keep a careful log on how you feel four hours after a meal. Using the diagnostic chart in Mastering the Zone, you can then further refine your own unique dietary needs based on how your body is responding, which in the final analysis is always the best. In other words, if you like apples and feel good after eating apples, eat them no matter what your blood type.