Research work on importance of proper functioning of sense of smell for a long life span. It says
" Thus, the production of saliva and digestive enzymes is stimulated before the actual food intake in order to prepare the gastrointestinal tract for the upcoming digestive process. In a healthy organism, this coordination depends on a dynamic balance between formation and degradation of proteins (proteostasis). This plays an important role for the recycling of cells and during the aging process."
This is a little disconcerting for those of us who have a poor sense of smell...
But the good news is that mannitol improve the sense of smell in 80% of PWP
I wonder if that's accurate. I know it's true that something like 80% of those who fully completed the ClinicCrowd study reported benefits, but the overwhelming percentage of participants never completed the study. I know some dropped out because of technical difficulties, but I wonder how many dropped out because mannitol was ineffective for them.
Perhaps olfaction is good for digestion, but in animal models, it has a negative effect on lifespan.
In flies, eliminating olfactory sensing increases lifespan:
the-scientist.com/daily-new...
In C. elegans (nematode) the same happens when chemosensory function is destroyed.
It's one of the nutrient-sensing systems that influences lifespan; less nutrients, longer lifespan.
Probably because they eat more if they can smell it because they can find it. So eating less is better for them. Like it is for us! But we can find as much as we want to eat at the supermarket so I am not sure that whether we can smell it or not makes a difference to the amount we eat.
The studies controlled for the amount of food eaten. The biochemical pathway is independent from insulin signalling, which is triggered by actual nutrient uptake. The research is summarized in the news article (linked above) both thoroughly and succinctly.
Interesting. Sorry I didn’t read it properly the first time.
This is interesting. Seems a good reason to take digestive enzymes just in case.
Do supplements strain or adversely effect the digestive system? 
Zhittaya June 2023 update
What do you think about \"Rapamycin\" 
Slow stomach emptying
