I am 30 years old, I like to play soccer, is it good if I start to take glucosamine to prevent join pain? Thank you

Yes, a little. While most studies on glucosamine focus on treating arthritis, and the results are mixed. However there is some research that suggests it may slightly slow progression of arthritis and is a decent supplement for joint health. There is no strong evidence to support, but some. Make sure to stay well hydrated while taking for best and safest result. Will not completely prevent oa, but could help.
No studies/no. There has been no studies that done since people who take lt do so because they r having symptoms. I have never seen it done before.
Doesn't work. Most of the data around glucosamine and chondroitin is from the veterinary literature. In people, results have been a lot less promising. It doesn't seem to prevent anything, and there is little to suggest that it will even treat or slow the progression of an arthritis once it gets going.