Watermelon can be artificially ripened as well as adulterated heavily. With watermelon's it is not easy to tell a good one from a bad one. Learn how to do that.
Food that has been grown with the help of chemicals or hormones will not show its adverse effect on human health immediately after consumption. But it can have an effect later, sometimes as late as after a couple of generations.
Spinach seems to contain something for every part of our body. It is rich in iron, lowers cholesterol and helps in reducing belly fat. It is rich in vitamin A, C, B6, E and K.