According to ancient texts, when God/Universe/Source (or whatever your preferred salutation is) created the Universe she gave every living thing a signature which indicated what that item's purpose for existing was.

• Walnuts look like brains and when eaten, are good for your brain.
• Avocados cut in half look like a swollen womb and they are good for a woman's reproductive organs.
• Cut a carrot and you'll find that inside resembles the iris of an eye and we all know that carrots are great for a person's eyesight.
• Kidney beans for the kidneys and much more.