Human: What are the best natural supplements for erectile dysfunction? Assistant: 
The best natural supplements for erectile dysfunction include ginkgo biloba, saw palmetto, L-arginine, and tribulus terrestris. Ginkgo biloba is an antioxidant that helps to increase blood flow to the penis, while saw palmetto can help reduce inflammation in the body, which may be a contributing factor to ED. L-arginine helps to increase nitric oxide levels, which are important for healthy blood flow to the penis. Lastly, tribulus terrestris has been found to improve sexual performance by increasing testosterone levels.