Read Blue Ocean Strategy before you do anything. Your business must swim in the blue ocean to have a good chance of success. You must clearly identify your target market. I'm in your target market. I spend >$2,000 annually on supplements, but I'm not going to a brick and mortar store to buy supplements. I'm buying online where the selection is better, the cost is lower, and I can read hundreds of reviews by other consumers. Plus, I do my research online before buying.
Adding a smoothie bar or whatever isn't going to make your store a hit. Do you think that no one in the history of nutrition stores hasn't already thought of that idea and tried it? A brick and mortar retail store might have been a good idea in 1990, but it's a tough way to make a living today unless you have a niche where you have no competition.
Here's a link to an overview of the Blue Ocean Strategy, but don't rely on it to think you understand the strategy. The book is filled with examples of companies that have successfully implemented the blue ocean strategy and the book might give you some ideas.
If you do decide to go forward with this idea, contact the local chapter of the Small Business Administration for some hand-holding.
Oh, and I think starting a retail nutrition store is a really bad idea... just in case that wasn't clear.