Hi and welcome to Mayo Connect - you asked "how do they get away with claim that it prevents alzheimer's or dementia??" This had been going on since the Wild West Days when "Miracle Cures" were sold by hucksters off the back of horse-drawn wagons.

Well, the short answer is anybody can claim anything - until a lawsuit is filed by an injured party or "cease and desist order" by a a government agency or the attorney for a harmed party.
And the Internet has made it easier than ever to do this under a cover of anonymity.

We understand that people faced with catastrophic or chronic illness are often desperate to find something, anything, that will help. Unfortunately, for many of them, there are no cures, no reversing the damage already done, no relief for everyday pain and loss. So, even though they hear the doctors saying "no cure" they will reach for anything that promises help, especially if it is endorsed by a celebrity, or they use buzz words lie "FDA Approved."

That is why some of us here at Mayo Connect take the time to do the research, figuring out if there are any independent reviews that prove or disprove the touted treatment, or if it might actually be dangerous. This one didn't pass any of the tests - see my post above.

Often, a developer will take a tiny seed of an idea (eg. certain scents can stimulate certain neurons in the brain) and create and tout a product. BUT, the next step should be unbiased testing to determine whether the product does what is says - preserves or improves memory in those with diagnosed Alzheimers - oops, they skipped that step. And transparency about who to contact - oops, failed again. Finally - "FDA Approved" - they have searchable databases - oops, failed again!