Found this interview with Howell.Very cool share. I'm sure there's something to it.
Probably the most remarkable thing I've heard Aajonus cite was the research of Howell on rats. It was very similar to Pottenger's work on cats. He was trying to prove that feeding rats cooked and processed food would shorten their life by 1/3rd, going from 3 years to 2 years.
He had the two study groups like Pottenger, one raw and one cooked... But in the first three year study, both groups lived to be 3 years old. Before running the experiment again, he realized that the cooked group was eating their own feces (I presume the raw group was as well).
So Howell put a wire mesh down for the second time around to prevent the rats from eating their own feces and sure enough the cooked group lived 2 years and the raw group lived 3 years.
To extrapolate that to humans, it might make the difference in 30 of 40 years of life for us.
He believes in the rate of living hypothesis of longevity, based on how fast you burn through your limited stores of enzymes.