Women’s Health FAQs

What is AlgaeCal?

Publication Date: December 19, 2018

By: NWHN Staff

Question: What is Algaecal?

Have you ever heard of AlgaeCal? I’m being deluged with ads saying any nutrient supplied in natural form, such as from plants, is better absorbed than nutrients supplied from rocks.


AlgaeCal is a calcium supplement produced by AlgaeCal Inc. that is made from red algae. AlgaeCal claims its supplements slow bone loss, increase bone density, and are easily digestible. They say that because the algae plant draws calcium and minerals from seawater, the calcium is “pre-digested” and is more bio-accessible and “bone cell friendly.”

Two main forms of calcium supplements are available: calcium carbonate and calcium citrate. These supplements are synthetic (created in a lab) or come from rocks such as limestone. These supplements dissolve when they come in contact with your stomach acid, and the calcium can be absorbed into your body. AlgaeCal claims that because their product is derived from plants, the degree to which the calcium is absorbed into the body (the bioavailability of the calcium) increases. However, calcium derived from algae is still just calcium carbonate, not a new calcium supplement form.

AlgaeCal posted four studies touting the effectiveness of their products on their website. While these studies reported positive findings, none present compelling evidence that AlgaeCal is significantly more effective at improving bone health than other calcium supplements. This article argues that supplements aren’t the way to go and that diet and weight-bearing activity have the most benefit in preventing bone loss. The National Women’s Health Network is also concerned about the study designs. Some of these studies are observational, so cause and effect cannot be determined. Others were tests done on bone cells (osteoblasts) or in mice and, therefore, may not apply to clinical studies. Physical activity, known to improve bone health, was also included in one of the studies as part of the treatment regimen. Therefore, further analysis would be required to determine whether bone density was affected by the AlgaeCal supplements, the activity, or the combination of the two. Furthermore, one of the studies measured bone mineral density after treating two groups with differing doses of AlgaeCal, yet the treatment regimen also included their Strontium Boost product. Strontium is similar to calcium and is thought to improve bone density. A prescription form of strontium ranelate to treat osteoporosis is available in Europe, but it has not been approved by the FDA. Strontium supplements (not the same as ranelate) are available over the counter in the U.S., but no studies show they are safe or effective. Taking strontium supplements can actually lead to inaccurate bone density tests later in life. All of these factors potentially skewed results, thereby making it difficult to draw any significant conclusion from these studies.

There is also a study from 2012 not included on the AlgaeCal website that looks at the difference in bioavailability between AlgaeCal and Caltrate600, but no results have been posted yet. Currently, there is no compelling clinical evidence to support AlgaeCal’s claims.

Additionally, the studies of the effectiveness when compared it to calcium carbonate and calcium citrate alone. It did not compare its effectiveness to common supplements that have a combination of other minerals, such as magnesium, zinc, and vitamin D3. These minerals are known to increase the bioavailability of calcium, and the presence of these vitamins and minerals in the AlgaeCal may increase its effectiveness. Therefore, the increased bioavailability of calcium would not be a unique feature, and would not be more effective than these common, less expensive alternatives.

The NWHN believes that additional clinical studies are needed to prove that AlgaeCal and calcium from red algae are significantly better than other calcium supplements. Given the evidence that is provided, as well as further research on the effectiveness of red algae for calcium, it is possible that AlgaeCal is, in fact, effective. However, there is not enough evidence to justify the higher cost of AlgaeCal, and more research must be done. AlgaeCal is safe for consumption but not significantly better than the less expensive, over-the-counter calcium supplements currently available.

Updated 11/13/2023 by Rachel Grimsley, RN, BSN, MSN, Nurse Writer

The information on this site is not intended or implied to be a substitute for professional medical advice, diagnosis, or treatment. All content, including text, graphics, images, and information on or available through this website, is for general information purposes only.

The continued availability of external resources is outside of the NWHN’s control. If the link you are looking for is broken, contact us at [email protected] to request more current citation information.


Get Involved

New ways to empower health care consumers across the nation.