The ability to digest starch may have given our human ancestors an evolutionary advantage in certain circumstances, according to an article by George Perry et al. in Nature Genetics. The enzyme amylase, secreted by salivary glands (and also by the pancreas), helps to hydrolyse or break down starch in the diet when mixed with water. The gene that produces the enzyme in saliva, called AMY1, is on chromosome 1, other authors have theorised that the salivary amylase gene evolved from the pancreatic amylase gene via an upstream retrovirus insertion.
Perry's team took salivary and DNA samples from people of Datog, Hadza, Mbuti, Biaka, Japanese, Yakut and European-American populations and analysed their typical dietary protein and starch intake. The results indicate that geographically distinct groups of humans tend to have variable levels of the AMY1 gene according to the level of starch in their diets: Those whose diets consist of higher protein levels tended to have on average fewer copies of the gene, and vice versa. More copies of the gene leads to a higher level of salivary amylase. Fruit-eating chimpanzees however have few copies of the gene. The authors suggest that: "This behavioral variation raises the possibility that different selective pressures have acted on amylase", i.e. it could be evidence for genetic adaptation to the availability of starch in the environment.
Another study in the American Journal of Human Genetics published just a month prior to Perry's article suggests that the gene for lactase persistence (LP, the ability to digest the lactose sugar in milk after childhood) came about through evolution of two groups geographically and chronologically distinct, and that "there is a still-ongoing process of convergent evolution" of the LP alleles in humans".
It appears that we are still evolving according to what we eat, but can our genes keep up with the pressures inflicted on us by modern western diets?
Announcing two lectures at the RDS in Dublin, Ireland. This year the date and location have changed, so check the website for details.
Both lectures are on Saturday 1st September 2007; in the first lecture at 1.00 pm Tom Greenfield ND will introduce the concept of the GenoType Diet in the forthcoming book by Dr. Peter D'Adamo ND. The venue is the Nutrition Theatre, places are limited.
In the second lecture at 4.00 pm Ingrid Greenfield of Artisan Bread Original will be demonstrating how to make sandwiches compatible with all blood groups, and samples for tasting will be available. The venue is Centre Hall.
Both speakers will be available at the Artisan Bread stand in the main exhibition hall on Saturday and Sunday.
There is a charge for entry to the event on the day, but free tickets can be obtained in advance from the website.
The IfHI Conference 2007 - The Buttes, Phoenix, AZ.
What a great conference: lots of speakers with new information on genetics and individuality, all giving the background information for the new concept revealed by Dr. D'Adamo.
The Book The GenoType™ Diet is to be on sale from December 26th, 2007. The concept takes us beyond blood types, to a new categorisation of 6 distinct genotypes:
Although these genotypes include blood group and secretor status information, they do not all exclusively relate to one single blood type: individuals fitting into certain genotypes may have one of several possible blood types. The new additions to the genotypes over and above the genetic information associated with blood types includes many easily accessible measurements:
D2-D4 ratio (second and fourth finger length)
Upper to lower leg ratio
These are associated with 'epigenetic' factors that do not change the actual genes of the individual, but influence how they are expressed, like a volume control that can be moved up or down to vary the amount that a certain gene interacts with the environment.
Other influencing factors on a person's genotype include both ancestral DNA haplogroups and ayurvedic doshas. It looks like the result will be the fusion of ancient wisdom, anthropometric techniques from the last century, and modern cutting edge genetic science - with a strong influence from the blood type information that is associated with diet and health.
Each genotype has different disease risks and health benefits, and the book will outline the best preventitive strategies for each type. It promises to be a new generation of naturopathic medicine.
The UK Human Fertilisation and Embryology Authority (HFEA) has agreed in principle to screening and selection of embryos for couples who have the possibility of passing on a gene for breast cancer.
Previously genetic screening has only been carried out for embryos with the risk of having a gene that always causes disease, such as cystic fibrosis.
Now the HFEA are allowing screening of genes on a case by case basis that would give the individual an increased risk of disease, such as the BRCA1 gene, which raises the risk of cancer in adulthood by 60-80%.
This kind of approach can be seen as a move away from human genetic diversity and the concept of addressing the environmental influences of switching genes on or off, towards a genetic inbreeding and the kind of uniformity depicted by Huxley.
A previous entry on this column described how polyethylene glycol could be used to 'hide' the blood group antigens on a red blood cell, turning any transfused blood into something that looks like O negative to the recipient's immune system. The entry also mentioned another method using the galactosidase enzyme, which can transform group B blood into group O by removing the galactose from the blood cell surface. The problem with the enzyme-based method was that the enzymes used for converting blood (taken from green coffee beans) were relatively inefficient, and a lot of enzymes would be needed to do the job, not necessarily at a neutral pH, which could be detrimental to the blood cells.
It did not therefore seem like an April fool joke when the journal Nature Biotechnology reported on April 1st a method of transforming any blood into blood group O. The paper announces the discovery of "two bacterial glycosidase gene families that provide enzymes capable of efficient removal of A and B antigens at neutral pH with low consumption of recombinant enzymes". The researchers described how two bacteria, Elizabethkingia meningosepticum and Bacterioides fragilis, contain enzymes that can remove both A and B antigens from red blood cells. This still does not address the problem of the Rhesus antigen on the blood cells of Rhesus positive individuals, which means that to make universal donor blood that is acceptable for anyone in an emergency (O Rh negative), the blood would have to be taken from Rhesus negative donors, who are in the minority compared with Rhesus positive individuals.
Patient trials will be needed before the blood group conversion method can be used in live situations to ensure that the IgM antibodies against opposing blood group antigens are not activated.