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.
And a supplement of 600 milligrams of calcium with 300 mg of magnesium daily is safe to take and may provide benefits. But you can get too much of a good thing from calcium supplements. One study showed men 50-71 who take a 1,000 mg daily calcium supplement increase their risk of dying from heart disease by 20 percent. The reason? Calcium gets into the lining of the blood vessels, making arteries stiffer. However, 1,000 mg of calcium a day from food is part of a bone and heart-friendly diet.