@ss66 I subscribe to Consumer Lab which is a website recommended by my integrative medicine physician at Mayo Clinic.

Consumer Lab:

-- consumerlab.com

I looked up the testing that Consumer Labs did on calcium products and their results. They did not test Green Calcium from Martin and Pleasance that you mentioned so I can't provide you with any data such as whether the claimed amount of calcium is equivalent to the actual amount of calcium and whether or not heavy metals were detected.

If you want to use plant based calcium then Consumer Lab did test and approved New Chapter® Plant Calcium Bone Strength however it is one of the more expensive products. They also tested and approved AlgaeCal Plus which is less expensive.

Since supplements are not regulated the FDA in the U.S. I believe it is wise to use a source such as Consumer Lab to figure out if the product label matched what is actually in the bottle.