Definitely an LLC.
It’s so easy and affordable to create an LLC these days that the pros (protection from personal liability protection for business debts and lawsuits) completely outweigh the cons (spending ~$500 and 10 minutes answering a few questions).
Do you really want that burden on your shoulders of potentially being personally liable if anything goes wrong with the supplements? As a sole proprietorship, all of your personal assets (banking accounts, cars, 401k, your house) are at stake in a lawsuit. An easy way to avoid that? Form an LLC.
Before, forming an LLC was a huge pain. You had to Google your Secretary of State, navigate their horrendous website to find the right forms, print them, fill them in, and mail it with a check and pray everything was done correctly. The alternative route was finding a lawyer to do it for you for $1500-$2000.
It was based on those experiences that I founded. Our legal marketplace allows startups to get legal stuff done by vetted attorneys at great rates. There’s a 100% money back guarantee (we’ve done 1000’s of these) too. I hope that helps! Feel free to message me directly if you have any more questions.