What is Doctor’s Best Vegan Glucosamine Sulfate with GreenGrown Glucosamine? Doctor’s Best Vegan Glucosamine Sulfate with GreenGrown Glucosamine helps support normal, healthy joint function and maintain healthy joints. GreenGrown Glucosamine is made using a patented fermentation technology and is free from allergens and suitable for Vegans, while most Glucosamine on the market is derived from shellfish. GreenGrown Glucosamine is tested and guaranteed pesticide-free. It is also manufactured to meet the highest USP grade of purity for Glucosamine.