In my opinion, web architecture has a lot of importance for SEO. You must keep your site as flat as possible. I see your website has 3 levels deep for a product page. That's OK. Furthermore, your website looks very intuitive.
I'm doing SEO for a supplements store too. So I want to share with you how I've considered optimize the website:
1. Divide your keywords in categories: main, secondary, category specific, product specific and branded in my case.
2. How I distributed my keywords:
-Homepage: main + branded (company name)
-Nav Menu pages: main + secondary
-Brands pages: main/secondary + branded (brand name)
-Categories pages: category specific + main/secondary
-Products page: branded (product name) + category name/branded (brand name)
I can tell you that with this method, the vast majority of our products are positioned in the first page for their names. A big number of categories in first page too. And we have only 3 levels deep for a product page too!!!
The more levels you include, the more disperse the link juice.
If, from a business point of view, you need more categories for making internal navigation more specific, then do it. But if you only looks for SEO benefits, consider the following:
Is it necessary to lose user's experience quality to gain more traffic? What will happen with these new users when they find the new navigation structure?
Hope it helps.
Sergio