Here's something I found, directly answering your question:
Is it unhealthy to run every day?
- Basically it's not unhealthy to run every day as long as you're in shape and have adjusted your body to the daily stress.
- Start out on soft surfaces for 4 months, increasing your mileage not more than 10% per week. This will help you to avoid shin splints and other injuries. Also be sure to stretch every day. Shin splints and stress fractures account for 70% of injuries in boot camp (though half of that is probably guys trying to get out of training)
- Once you've been running every day switch off between soft surfaces and concrete since you'll be running on concrete in boot camp.
- Take it easy at first, stretch always, and quit smoking.