The problem with Pesticides is that they are mostly neurotoxins which harm the bees who can't get back to their hives and people with Alzheimers and senile dementia

 So, there is less chance of ANY form of senile dementia or Alzheimers if you only eat organic food that either you grow or you buy at a farmer's market or Whole Foods or something like that. So, if you can only eat organic foods so you can live a long and healthy life without it being cut short by pesticides that contain neurotoxins in your food. 

Also, another problem is that these neurotoxins concentrate into the flesh of animals people eat too along the way. So, unless your meat of all kinds is fed organically you are getting high concentrations of pesticide from their flesh as you eat it.

So, if you want your brain to actually work a long time you want to be eating organic foods without any pesticides and if you want to eat any meats you want these meats to ONLY be eating organically grown grains too.

Since all of us could be alive 100 to 500 to 1000 years from now because of Medical AI advances this is something to think about carefully if you want to be okay past about 50 years old.

Another helpful thing is taking sublingual B-12 from Trader Joe's or anywhere else. however, after 40 or 50 you need only sublinguals if your stomach no longer processes B vitamins from the meat you eat and if you are a vegetarian it is even more important to take sublngual B-12 to keep both brain and body working right after 40 or 50 years old too.