A 2013 science paper gets it wrong about dogs and a need for starch
Rebuttal of ” The genomic signature of dog domestication reveals adaptation to a starch-rich diet” paper
This is part two of a critique of a 2013 paper that purported to investigate the evolution of the domestic dog, and ended up just being a support piece for feeding your dog inappropriate starch food. This is part two of the review that looks at the WORD detail of their paper (not just the fancy maths).
PAPER – “The breakdown of starch in dogs proceeds in three stages: (1) starch is first cleaved to maltose and other oligosaccharides by alpha-amylase in the intestine; (2) the oligosaccharides are subsequently hydrolysed by maltase-glucoamylase, sucrase and isomaltase to form glucose; and (3) finally, glucose is transported across the plasma membrane by brush border protein SGLT121.
HDT – yes that is the process in starch being used in any animal that ingests it, The main question is still whether this process is very efficient or pronounced in dogs (carnivores) versus animals originally evolved to eat starches like rabbits and humans.
Let alone all of the other benefits that eating meat give these original carnivores (which of course was NOT part of this research). Just because a dog can TOLLERATE starch, doesnt meant that we should force them to have a starch diet (for the sake of making dog food companies rich). Its your dogs health we are talking about after all …
PAPER – “Whereas humans have acquired amylase activity in the saliva via an ancient duplication of the pancreatic amylase gene, dogs only express amylase in the pancreas.”
“In dogs the AMY2B gene, encoding the alpha-2B-amylase, resides in a 600-kbCDR on chromosome 6 with Z(HP) andZ(FST) scores of 24.60 and 7.16, respectively. Interestingly, an 8-kb sequence spanning the AMY2B locus showed a several-fold increase in aligned read depth in dog relative to wolf (Fig. 2b), suggestive [not conclusive] of a copy number change. Formal comparisons of regional and local pool coverage, and wolf and dog coverage (Methods), respectively, also suggest a substantial increase in copy numbers in all dog pools compared to wolf at this locus.”
HDT – as you can see this paper is heavy in molecular terms as it should be, but as they have also stated “Whereas humans have acquired amylase activity in the saliva via an ancient duplication of the pancreatic amylase gene, dogs only express amylase in the pancreas.”
This is one of the major differences raw meat dog foodnutritionists are aware of between humans (omnivores) any herbivore AND dogs (95% carnivore) – DOGS have the amylase activity in their Pancreas ONLY- so the breakdown of starch does not occur during chewing of the food, which is where it occurs in humans, because proper breakdown of starch can take a long time. Ideally it should occur as soon as possible, not be left to the intestinal tract.
DOGS MISS the SECOND STEP OF STARCH DIGESION
PAPER – “Maltase-glucoamylase is responsible for the second step in the breakdown of starch, catalysing the hydrolysis of maltose to glucose. No copy number changes were observed in the MGAM locus (FOR DOGS) so we decided to study haplotype diversity across the region to facilitate the identification of causal variants.”
HDT – While their alternative theory and research gave them hope that the science supported their theory, the most obvious analysis method they used in step 1, ” copy number changes” could not be used. This suggests that any observation by lesser methods is also likely to prove a weaker link to their proof. Just because high maths suggests something is possible, DOES NOT MEAN in the real world that it is true or even desirable.
DOG STARCH PROCESS STEP THREE – INVALID
PAPER- “Once starch has been digested to glucose it is absorbed through the luminal plasma membrane of the small intestine by the sodium/glucose cotransporter. To benefit from an increased capacity to digest starch, dogs would therefore be expected to show a parallel increase in glucose uptake. Heterologous expression analysis29 shows that glycosylation at a nearby site (residue 248) affects glucose transport, indicating that it is possible that dogs acquired improved glucose uptake as a result of the observed substitution. In addition, we see only non-significant differences in SGLT1 expression in pancreas of dog (n59) and wolf (n54) indicating that selection primarily targeted a structural rather than regulatory mutation in SGLT1.
” In conclusion, we have presented evidence that dog domestication was accompanied by selection at three genes with key roles in starch digestion: AMY2B, MGAM and SGLT1.”
HDT- STEP 3 SHOWS NO DIFFERENCE BETWEEN WOLVES and DOMESTIC DOGS at a gene level, so the evidence is very weak.
WHY DOGS NEED MEAT, and What the gene mutations dont tell you
The maths and chemical testing of the scientists is fine. Even innovating the maths is probably acceptable (wait for future peer reviews on that) from a laboratory point of view, BUT as you can see the research for all its cleverness is NO WHERE near 100% conclusive, of how well dogs utilise carbohydrates let alone grain.
The whole reality with dogs eating grains is not “can they do it” (obviously dog food makers have been making dogs eat inferior protein sources such as grains for decades). But the question of whether it is good for the dogs.
Did you know that a lot of humans can tolerate the increased gluten in wheat caused by modern farming methods (x3 + gluten), but many people are either gluten intolerant or celiac (2% of the population), most likely because of this HUMAN purposely increase of GLUTEN. In fact almost ALL people could be said to tolerate (don’t instantly die) from the increased amount of gluten in man made products, but it sure is NOT healthy for the majority of humans.
THE PAPER complete avoids discussing whether it is “good” for the dogs to eat grain and vegetables. Just that MAN most likely FORCED them to change diet, and they unsucessfully tried to show how well dogs have adapted to that.
Why is it necessary to feed your dog an inferior food source if you can afford to feed them what they were evolved to eat? This paper suggests a semi adaption occurred so that dogs don’t get sick (or at least can extract some nutrition from starch), but it is VERY obvious that nowhere near the full evolution has occurred. That evolution that herbivores took on to have in their digestive system to handle a massive grain or carbohydrate load. This paper mainly compared domestic dogs to wolves (full carnivores).
Part 3 of this paper reviews the final part of this pro grain dog food paper.
Reference
The genomic signature of dog domestication reveals adaptation to a starch-rich diet 2013
Erik Axelsson1, Abhirami Ratnakumar1, Maja-Louise Arendt, Khurram Maqbool1, Matthew T. Webster1, Michele Perloski, Olof Liberg, Jon M. Arnemo, A˚ ke Hedhammar6 & Kerstin Lindblad-Toh
