Customers prevagen reviews typically don't go to well, despite what the marketing and their own funded studies would have you believe.
They have previously been targetted by the FTC for making unstubstantiated claims . And Prevagens battle with the FTC is still ongoing, with the last update being in 2021. The FTC highlighted that Prevagen's performance claimes were based on the Maddison Memory Study, which the FTC stating "The Madison Memory Study failed to show a statistically significant improvement in the treatment group over the placebo group on any of the nine computerized cognitive tasks," 
The FDA did also issue Prevagen a warning letter over the use of the ingredient apoaequorin and whether or not it qualified as an ingredient that should or should not be regulated in 2012, with another element of the FDA warning letter referencing the testamonials used on Prevagen's website previously referenced medical conditions. in 2018 the FDA issued a press release marking their warning of Prevagen as resolved.
The supplements do contain vitamin D which could actually have some mild improvements towards brain function, but in general Prevagen has had a long enough history of issues that we personally would avoid it.
Prevagen has had something of a hard time, and ultimately their aggressive marketing has come back to haunt them.
As we've mentioned Vitamin D can help with mood and has other benefits and that can help with brain fog , but if you're only getting the vitamin D boost to improve cognitive function, then well you can get a vitamin D pill for an awful lot cheaper than prevagen without the issues.
The legitimate customers prevagen reviews we found as you'd suspect have been nothing short of an unmitigated disaster for the company. Many complaining of side effects and oh so shockingly, saying it doesn't work with a study population that showed no statistically significant improvement, this comes as a total surprise. As dietary supplements go, this one is poor.
Of course the reviews were bad. There's a lot of blatently fake reviews on Amazon, but it's not surprising that a company with a budget like Prevagen would invest in this.
We answer some of the most commonly asked questions about Prevagen.
No, the FDA does not regulate dietary supplements. The FDA previously had concerns of medical overeach, but this has since been addressed.
Vitamin D3 is all well and good, we don't really have any complaints here, most americans are deficient and supplementing for vitamin D can improve memory and brain health.
Apoaequorin is where the problems come in. Apoaequorin is a calcium binding protein found in luminescent jellyfish, the thought process behind using it as a supplement for brain health is that calcification in the brain is related to declining cognitive function. Especially large build ups of calcium stones. The compound is very similar to the naturally occurring human protein calmodulin, which does the same thing and is believed to have further impact on memory.
Unfortunately for this dietary supplement it seems that apoaequorin is taken orally it can not cross the blood brain barrier and thus never actually makes it to the human brain, it's simply broken down in the stomach.  However, this does lend some some defence against wireds claimed that the ingredient is particularly dangerous made by Wired in reference to an obtained document from 2012. (see image right). It does however seem that Prevagen did address the FDA complaints with exception to medical overreach in promoting a supplement for medical conditions. See image from the FDA letter to prevagen referring to safety concerns as published by wired. And the extract from the FDA letter concerning it's concerns over claims regarding medical conditions.  In June 2018 the FDA issued a statement saying that prevagen has resolved the issues from the 2012 warning letter with only one concern from their last investagation "regarding insufficient documentation to prove the company reported serious adverse events" - wired.
Although commonly reported side effects in customer reviews of Prevagen included everything from dizziness and nausea, through to cardiovascular issues and ironically memory problems.
Whilst, they claim that they never intended Prevagen to be used to people struggling with severe memory issues from conditions like alzheimer's disease, they heavily implied that Apoaequorin would make a notable difference.
Of course it dosn't. Taking prevagen won't help clearer thinking or word recall as they claimed and it's more likely to harm you than do anything to aid with healthy brain function.
Don't buy Prevagen, for the good of your own health and wallet. We have absolutely nothing good to say about this supplement. Products like Prevagen and their false claims do nothing but harm the entire health sector. It's been such an issue that there are now calls for further regulation on the industry.
Although we can see the appeal after all of the issues. As a rule of thumb, the europeans have more regulations on what supplements manufacturers can claim to be clinically proven, or actually aid brain health. So if the product isn't on sale there, then there's definitely more risk of buying a dud.
1 - https://www.ftc.gov/news-events/news/press-releases/2017/01/ftc-new-york-state-charge-marketers-prevagen-making-deceptive-memory-cognitive-improvement-claims
2 - https://www.reuters.com/article/quincybioscience-ftc-memorypills-idUSL1N1EZ13E
3 - https://www.wired.com/story/prevagen-made-millions-fda-questioned-safety/
4 - https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6132681/
5 - https://www.ncbi.nlm.nih.gov/books/NBK552157/