Berkeley Wellness Alerts

Blue-green algae are among the most ancient life forms on earth. More accurately called Cyanobacteria, they are now also popular dietary supplements. There are many kinds of algae, and though Cyanobacteria were once grouped with true algae by biologists, they are now recognized as a separate phylum. They contain protein, some vitamins and minerals, and other compounds. They are rich in chlorophyll, a pigment that enables plants to manufacture sugars from solar energy. But there’s no convincing evidence that chlorophyll does anything for the human body.

While algae are an essential part of the food chain, blue-green algae (also known as pond scum) are not generally eaten by other aquatic organisms. The question is whether they—packaged as capsules, pills, and powders—provide any special nutritional or medicinal benefit to humans. When we last reviewed this question in 2004, we said no. There has been some research since then. Is it time to change our minds?

The two main types of blue-green algae are Spirulina and Aphanizomenon flos-aquae (AFA), both naturally present in lakes and streams. Blue-green and other algae are used as human food as well as animal feed in China, Japan, and many other countries. They are also packaged and sold in health-food stores and drugstores and on the Internet. In this country AFA is harvested chiefly from Upper Klamath Lake in Oregon, where it is freeze-dried and turned into capsules.

Skimming the health claims

The claims made for blue-green algae supplements are limitless—they are said to be nutritionally superior to ordinary foods, and medicinally superior to drugs. Marketers promote them as a treatment or preventive for everything from heart disease and cancer to hyperactivity in children and Alzheimer’s disease, but there is no credible research to support these claims. The algae do, of course, contain nutrients, which vary, depending on where the algae grow and other factors. In any case, the supplements usually contain only tiny amounts of algae.

There has been some interesting research on blue-green algae in recent years. For instance, a small study in Korea, in Nutrition Research and Practice in 2008, found that elderly people with diabetes who took Spirulina supplements had reductions in blood pressure and blood cholesterol over a three-month period. Other small studies have found that Spirulina could reduce nasal symptoms in those suffering from allergic rhinitis. But this is preliminary research and does not support the extravagant claims made by marketers of the supplements.

It’s well known that blue-green algae can produce micro¬cystins and other toxins that can contaminate drinking water and, in large amounts, make people sick and kill livestock and pets. Over the years Health Canada (the equivalent of our FDA) has tested a broad range of algae supplements for microcystins. They found no toxins in Spirulina, though other blue-green algae products did sometimes contain them. Health Canada warned against giving non-Spirulina algae products to children.

Bottom line: You don’t need blue-green algae supplements. Even if they are pure and free of toxins, it’s a stretch to think they’ll keep you healthy. Get your nutrients from vegetables and fruits, which taste better and cost a lot less than algae.