Yoga exercises could stimulate the passage of (green) food and/or (originally green) bile through your bowel, and then either the food or bile would color the stool green. If stools are loose and contain undigested food, you are losing nutrients this way.
Excessive use of magnesium supplements can be toxic. The upper limit -- the highest dose a person can take -- of magnesium supplements is: 65 mg/day for children ages 1-3. 110 mg/day for children ages 4-8. 350 mg/day for adults and children ages 9 and up.
Magnesium dietary requirements for cows range from 5,000 to 10,000 milligrams per head/day. Purchased minerals that contain 5% magnesium contain 1420 milligrams per/ounce. Formula for Converting % to Milligrams per Ounce (mg/oz.) Example: The mineral bag label list the Phosphorus to be 12%.