Aside from the lumber itself, the only other materials used in making your butcher block are all considered food-safe once cured:
1. Titebond III Wood Glue - FDA Approved and Waterproof
2. Loctite Epoxy (used to fill small knots)
3. Goodfilla's Water-Based Non-Toxic Wood Filler (used to fill small knots)
4. And last but not least, your selected finish
That's the complete list. Hopefully this is helpful!