I've been contemplating starting a brain supplement product similar to Onnit's Alpha Brain.
The supplements industry is ridiculously de-regulated (thanks Utah). Literally anyone can contract a manufacture and hand them a mix of natural ingredients to get in business.
What legal considerations I should keep in mind before venturing out in such a business? Can a supplement's formula be patented?
With any ingestible product, you'll always be taking on more risk. Tim Ferris' first startup was a brain supplement as well, BrainQuicken if I recall correctly.
The biggest key in such a business is finding the right manufacturer. Two things you need to look at:
From a quick google search, I see a few provide insurance that'll cover you: Now Foods, Nutricap Labs, Vitalabs
Apart from the insurance, keep these things in mind as well:
This is a very high margin business, but the key, like all businesses is branding and marketing. Create a genuine product backed by medical research and it's possible to generate a large amount of revenue very quickly.
Here is a video interview of a UCBerkley student who sold $500,000 worth of supplements on Amazon in a matter of a week (after some fad supplement was mentioned on the Dr. Oz show) and now runs a successful supplements business where he has created his own brand (like you intend to):