Calcium Citrate + Vit D3 is made from 100% dietary sources, not synthetic, and does not carry any risk of lead poisoning. It is highly soluble and can be taken without food. It does not require stomach acids to dissolve, unlike calcium carbonates that have to be taken with meals. Suitable for those on vegan, vegetarian and low calcium diets. Great for elderly and those who suffer from atrophic gastritis, peptic ulcers and GERD.