FYI, I posted this on 2 PD Facebook groups yesterday:
I started taking mannitol 2 weeks ago. I purchased it in bulk from Amazon, and I add 1 tablespoon to a cup of hot organic decaf tea every night (I drink several different types and brands of tea). I've read that it's good to take it with coffee or tea that's caffeinated but haven't been doing that yet.
My sense of smell has been GONE for 2 years and was very disordered prior to that (problems began after a head injury in 2003). My sense of taste has also been extremely diminished as a result.
About 5 days ago my husband brought coffee into the bedroom in the morning while I was still asleep, and the smell of it woke me up.
Since then I've been smelling things off and on throughout the day. It's been so strange... I had almost forgotten how a lot of things smell. My 14 y.o. washed her hair, and when she walked near me in the kitchen, it smelled so good! We also made burgers on the grill for dinner, and I could actually taste them.
I don't know what to make of this. I keep thinking that maybe it's just psychosomatic, but because it happens so unexpectedly while I'm busy and not even thinking about it (or sleeping!), it doesn't seem like I could be imagining it. I thought that if I was going to see improvement of any sort from taking mannitol, it would take at least a few months.
The only negative side effect I've experienced so far is a slight bubbling/bloating feeling in my gut, but it's barely noticeable and goes away about an hour after I drink my tea. I've read that taking enzymes with the mannitol helps with that, so I'm probably going to try that soon.
FYI, I began having PD symptoms in 2015/2016 and was diagnosed in August of 2018. I'm 54 and 112 lbs. I take no Rx meds, just basic supplements and high-dose thiamine hcl since November of 2018 (1 gram/day, but I skip a day once a week).
UPDATE: LAST NIGHT
My husband bought a new brand of loose-leaf Earl Grey tea 3 weeks ago (about a week before I began taking mannitol). I opened the tin and put it right up to my nose and sniffed but couldn't smell anything at all. Last night (June 7) I decided to try again to see if I could smell it. I put my nose right up to the tin again and sniffed hard, not expecting to smell much of anything. The smell was so unbelievably strong that I started coughing and sneezed lol. I'm smelling so many things now that it's overwhelming after being "nose blind" for 2 years.
I also SLEPT last night without medical cannabis for the first time in nearly 2 years. Without THC, it takes me 4-5 hours to fall asleep, and I only sleep 4-5 hours before waking up again. Last night it took me less than an hour to fall asleep. I woke up briefly a few times but got a total of almost 8 hours.
Uridine - from my experience..
Thiamine HCL and Mannitol concern 
Mannitol and the blood brain barrier
