Considering how far removed from its "natural" source much of our food is, I don't think Soylent should be looked at with much skepticism. Additionally:
> Calcium carbonate is the most common and least expensive calcium supplement. It should be taken with food, and depends on low pH levels (acidic) for proper absorption in the intestine.[26] Some studies suggests that the absorption of calcium from calcium carbonate is similar to the absorption of calcium from milk