Newly-published hypothesis on horseradish and radish peroxides being partially behind the sometimes observed association between fish consumption and delayed cognitive decline

Yesterday, my newly-published hypothesis on horseradish and radish peroxides being partially behind the sometimes observed association between fish consumption and delayed cognitive decline went live online.

Here's the link: http://www.sciencedirect.com/science/article/pii/S0306987717301238  I believe the full article will be free online for the next 49 days.

And here's the title and abstract:

Horseradish and radish peroxidases eaten with fish could help explain observed associations between fish consumption and protection from age-related dementia

Medical HypothesesVolume 107, September 2017, Pages 5–8

Abstract
A juxtaposition of regional cuisines and recent prospective studies of fish consumption in China and Japan points to fresh horseradish and/or radish (HRR) as possible contributors to delaying age-related dementia. The hypothesis is that the inverse association found sometimes between fish intake and cognitive decline is partially due to exposure of the oral cavity to active peroxidases from HRR served in conjunction with fish. This hypothesis can be tested by specifically looking at whether HRR is consumed with fish and whether such HRR is prepared in a way that preserves activity of HRR peroxidases. It is possible that by putting active HRR peroxidases in their mouths, elderly people supplement their age-diminished salivary antioxidant capacity and break down additional hydrogen peroxide (H₂O₂) in the oral cavity before it can migrate into the brain, thus decreasing the incidence of brain cell death induction by chronically-elevated H₂O₂. Intentional exposure of the oral cavity to active HRR peroxidases could be a prophylactic for delaying dementia. Because vegetable peroxidases are inactivated by gastric juices, it will be difficult to obtain benefit from HRR peroxidases’ antioxidant effect via ingestion in encapsulated dietary supplements.

I first noticed the possible involvement of horseradish back in September 2016, which I discussed in the post "Down the research rabbit hole and finding a root." Afterward I kept coming across more evidence that supported that idea: evidence of the importance of hydrogen peroxide in oxidative stress, the often nonlinear nature of oxidative stress damage, plausible anatomical pathways for hydrogen peroxide in the mouth to affect the brain (especially via the cribriform foramina) in ways connected to age-related neurodegeneration, and differences in cooking methods and diet from country to country. So I decided to put it together into a medical hypothesis and submit it for publication in hopes that researchers would test the hypothesis.

The journal Medical Hypotheses is peer-reviewed, and one of the peer reviewers clearly hated my hypothesis initially. However, I revised it to include new evidence and explanations, and the reviewer grudgingly accepted that the hypothesis was adequately supported by reported evidence and approved it for publication. That's why it took over six months from submission to publication. However, I'm glad for the criticisms in the peer review process, for they made me address and resolve key issues in the hypothesis.