Kinesiology
I urge everyone to learn this extremely simple method of finding out if a substance, food, drink, medicine, or device etc is good for your body......

http://www.youtube.com/watch?v=dJtdD9AJ_Hc

The video participants show holding the substance in question at the heart level. I was taught this technique back in the early 80's, and was taught to hold the substance at  navel level. The naval level is the location of the solar plexus and home to the body's radar system.
The body comes equipped with an ability to sense and read everything it comes into contact with before it actually makes contact. It can scan at least 30 feet in front of it. If you desire, you can learn to use this. It's the reason why some people will suddenly feel as if they should not enter an area... or they get butterflies in their stomach, etc.

Everyone needs to learn, become aware of, work with, and understand the Body has it's own defense mechanisms built in. The body is a separate unit from us. We "occupy" our bodies as a courtesy; we are akin to parasites. The body always strives to protect itself from harm and exist in harmony but "we" as parasites, always tend to override the body's desires and force it to follow our dictates.

Today; because of the tremendous toxins in our foods, air, water, technology and prescribed medications we have placed our Bodies in a precarious situation and a greatly weakened state.
Here is a second method of testing if a substance or device is good for your body.
Muscle Kinesiology:

http://www.youtube.com/watch?v=gEcyh6ZmJso&feature=related

I prefer the Sway Method because you can do it by yourself.
A word of precaution when using either method. Calm your mind before using. You want to avoid as much as possible your "ego's" ability to "color" the outcome. So just relax your mind before using.  It should only take about 15 to 30 seconds to calm down and clear out.