Plankton fossils, particularly those known as diatomaceous earth or calcareous microfossils (from coccolithophores and foraminifera), are natural sources of minerals, notably calcium and silica. The use of fossilized plankton as a calcium supplement is justified by its high mineral content, especially in products specifically processed for human consumption. Several studies have shown that bioavailable calcium can be derived from marine sources, including fossilized microalgae and plankton, making them a potential alternative to traditional calcium supplements such as calcium carbonate or citrate.

Research indicates that marine-derived calcium, including that from plankton fossils, may be absorbed efficiently in the human digestive tract. For example, a 2017 review in the journal Marine Drugs discusses the bioavailability of calcium from marine sources, including fossilized remains. These supplements are sometimes promoted for bone health and to support calcium deficiency. However, direct head-to-head clinical trials comparing fossil plankton calcium sources with conventional supplements are limited, and most evidence comes from compositional analyses and animal studies.

In summary, the use of plankton fossil as a calcium supplement is primarily scientifically justified due to its mineral content and bioavailability, but high-quality human clinical evidence is still limited, supporting a moderate evidence rating.