Algae encompass a wide range of aquatic, photosynthetic life, from single-celled phytoplankton to large seaweeds. Due to this vast biological diversity, the calcium content varies dramatically, though some specialized species accumulate significant concentrations. This has led to the development of plant-based calcium supplements, offering an alternative to traditional mineral sources. Interest in algae as a source of this mineral is driven by the potential for a more bioavailable and mineral-rich compound for human consumption.
The Specific Algae Used for Calcium Supplements
The primary commercial source of algae-derived calcium comes from a specific group of calcified marine plants known as coralline red algae, belonging to genera such as Lithothamnion and Mesophyllum. These organisms flourish in pristine, cold-water marine environments, including the North Atlantic around Iceland and the coastlines of South America. The algae naturally absorb minerals from the surrounding seawater and incorporate them into their skeletal structure through a process called biomineralization.
The result is a hard, porous structure composed largely of calcium carbonate, which can reach calcium concentrations as high as 31% by weight in the dried material. After the algae complete their life cycle, their skeletal remains detach and collect on the seabed, forming mineralized deposits that are sustainably harvested for supplements. This material is often marketed under brand names like Aquamin or AlgaeCal, distinguishing it from general sea vegetables due to its exceptionally high mineral density.
The Unique Structure of Algae-Derived Calcium
Algae calcium is chemically composed of calcium carbonate, similar to calcium derived from ground limestone. However, the physical structure of the algae-derived compound is what differentiates it from rock-sourced supplements. The material retains a unique matrix from the original plant, often described as having a porous or honeycomb-like architecture.
This distinctive physical structure is hypothesized by some researchers to enhance the body’s ability to absorb the calcium compared to dense mineral salts. Beyond the calcium itself, the mineral matrix naturally includes a broad spectrum of other trace minerals, which can number up to 74 or more, depending on the species and source. These co-factors, which include magnesium, strontium, zinc, and selenium, are naturally incorporated into the structure. The presence of these multiple elements is considered beneficial because they are known to play supporting roles in bone formation and mineral metabolism.
Calcium Levels in Common Edible Seaweed
While the calcified red algae are utilized for high-concentration supplements, other types of commonly consumed whole-food algae, or seaweeds, also contain calcium, though in much lower concentrations. These edible varieties include brown algae like kelp and wakame, red algae like nori, and the microalgae spirulina and chlorella. The calcium content in these sea vegetables is highly variable and depends on factors such as the species, the season of harvest, and the environment in which they grew.
For instance, raw wakame and kelp contain a moderate amount of calcium, with values around 150 to 168 milligrams per 100-gram serving in their raw form. This equates to less than 1% of calcium by dry weight for many of these varieties, which is a significantly lower concentration compared to the over 30% found in the calcified red algae used for supplements.