If you place a product in retail stores, you'll do this through an aggregator.

There are only a few in the US.

You'll likely have to discount supplements by 60%-80% of retail to interest an aggregator.

So likely your way better off selling directly to consumers.

Better meaning you'll require producing far less product for far more profit.

Consider using Facebook Ads or Traffic Oxygen or Kickstarter for product testing.

Sell product through Amazon FBA, if you prefer to avoid fulfillment challenges.