The point is to look at the topic each day and ask yourself "Do I know anything about this?" If you do, write a hub on it. You have the option to write between 1-3 hubs on the topic, not more than that.
Some people do happen to know random health stuff. I looked through the list and saw that I knew things about maybe 5 of the topics and with a little research I would know about a few more of them. I plan on just writing what I know about. No one says you have to participate in it.
This contest is a way to push your knowledge. Some people need a challenge to help them find things to write about, I know I do. It's easier to write about a specific topic than to have someone tell you to just write.