I like the Jarrow Formulas Bone-Up calcium supplement. I think that Jarrow Formulas does a lot of really good research into how vitamins and supplements are best created so that they absorb into our bodies. Since so many vitamins don't easily absorb and just go right through it is nice to think that I might be getting more calcium in my body by taking the Jarrow Formulas Bone-Up. It includes all sorts of different ingredients that the big box store companies haven't thought to add. (Or wanted to pay for it). I have read that etween 2%-4%of a person's skeleton is remodeled every year! Meaning that calcium and other minerals leave the bone in a process called resorption and then must be "remodeled" or replaced. Due to poor nutrition or reduced hormone levels with the onset of aging, the loss of calcium and other minerals from the bones creates tiny holes that make bones weak and brittle. So it seems that keeping that healthy with the Jarrow Bone-Up Formula might a good idea. Exercise helps a lot too! There was a study done in England that concluded this: In 1982, an important calcium supplementation study was concluded and reported by the Dept. of Medicine and Radiology, Royal Free Hospital in London, England. Fifty-three women with reduced calcium absorption and accelerated bone loss were separated into three groups and studied for over 14 months. At the conclusion of the study, only the women that received 1,000 mg of calcium from ossein hydroxyapatite (OHC) along with vitamin D showed significant support for bone-health The Jarrow Formulas Bone-Up calcium supplement does contain the ossein hydroxyapatite (OHC) as well as Vitamin D3, zinc, copper, Vitamin K, Boron, manganese and Magnesium. All of which seem like they may be an important part of absorbing the calcium which I take. I like and trust the Jarrow Formulas and I use their Bone-Up calcium supplement as one of the choices I use when I take calcium for my aging middle aged bones.