Soy milk and kids. There are no definite studies about your soy milk and it having delterious side effects. There is a lot of info. On the web about soy milk causing cancer, obesity, etc. If your child is not able to tolerate regular milk, you may not have a big choice but in moderation I have not seen it being harmful. Soy formulas have been around for very long time. A glass of soy milk a day for older kids may not.