If it actually affects my brain in a negative way, I would really like to know about it, so VOI is high.

In order to determine the VOI, you need a path from the information to a change in action, with a probability that you'll act differently and an expected value if you do. Both of these are small; the evidence seems to indicate that fluoride is okay, and even if fluoride does affect your brain negatively, the effect size would have to be very small to have escaped detection, and it would have to be weighed against the additional expense of drinking bottled water. (And yes, very-minor brain damage and money are fungible, since you money can buy books and classes and free time and intelligence-enhancing drugs.)