How can Shopify help us address specific marketing to specific countries, particularly for food/dietary supplements?
You can tailor your buyer experience using Markets (in your shop admin, in the left-hand navigation section). A Market is a place for you to set the buyer experience across a set of countries, or a single country.
If you want to have different products for sale in specific countries, you can use market-specific catalogs. This is useful if you sell products that are allowed for import into certain countries, but restricted in others.
You can use a translation tool to change languages or translations per market. Even within English, some products will have different descriptions in American versus British English.
Depending on your Shopify plan, you may also have access to customized Themes per Market.
These are the most common tools that you would use, but you can also view the full list of international tools here.