Q: Are calcium supplements derived from algae better than other types of calcium, as advertised?
A: We’ve seen no good research to support the claims. Several pricey calcium supplements get the mineral from marine algae— that is, seaweed. Many questionable claims are made about the superior absorption and efficacy of these supplements for bone health. Their basic message is that “plant calcium” is better (“more body friendly”) than standard calcium that comes from “rocks,” even though all calcium can be traced back to the earth’s crust (that is, rocks).
These supplements also contain other minerals naturally in the seaweed (such as magnesium) and often other added bone-health nutrients (such as vitamins D and K, boron, strontium, and various trace minerals).
The studies cited by the manufacturers, most funded by them or involving researchers employed by them, prove very little since they don’t include a comparison group (using either a placebo or other calcium supplement), and the modest improvements in bone mineral density could have been due to other nutrients in the supplement, for instance, or to the extra exercise the subjects undertook. Other research cited was done in labs on isolated bone cells or in mice and may have no relation to what happens in people.
We can’t recommend algae-based supplements over standard forms of calcium, since there are no well-designed studies comparing them in terms of efficacy and safety. It’s impossible to know what effect, if any, the additional nutrients in the supplements have. There are many other “bone health” formulas out there, containing everything but the kitchen sink and making similar claims—with no convincing clinical support.
Get as much calcium from your diet as possible, and if you fall short, stick with calcium carbonate or calcium citrate supplements. And consider taking a separate vitamin D supplement.
Also see Calcium Supplements Are...Safe?