Algae are a large and diverse group of simple, typically autotrophic organisms, ranging from unicellular to multicellular forms. The largest and most complex marine forms are called seaweeds. They are photosynthetic, like plants, and "simple" because they lack the many distinct organs found in land plants. Though the prokaryotic cyanobacteria (commonly referred to as blue-green algae) were traditionally included as "algae" in older textbooks, many modern sources regard this as outdated and restrict the term algae to eukaryotic organisms.
All true algae therefore have a nucleus enclosed within a membrane and chloroplasts bound in one or more membranes. Algae constitute a paraphyletic and polyphyletic group, as they do not all descend from a common algal ancestor, although their chloroplasts seem to have a single origin.
Algae lack the various structures that characterize land plants, such as phyllids and rhizoids in nonvascular plants, or leaves, roots, and other organs that are found in tracheophytes. They are distinguished from protozoa in that they are photosynthetic. Many are photoautotrophic, although some groups contain members that are mixotrophic, deriving energy both from photosynthesis and uptake of organic carbon either by osmotrophy, myzotrophy, or phagotrophy.
Some unicellular species rely entirely on external energy sources and have limited or no photosynthetic apparatus. All algae have photosynthetic machinery ultimately derived from the cyanobacteria, and so produce oxygen as a by-product of photosynthesis, unlike other photosynthetic bacteria such as purple and green sulfur bacteria.
Blue-green algae supplements come in the form of capsules, pills, and powders. An important part of the food chain in lakes and ponds worldwide, blue-green algae are microscopic plants with characteristics of both bacteria and algae (such as seaweed), but are more closely akin to bacteria. The two main blue-green algae types are Spirulina and Aphanizomenon flos-aquae (AFA). AFA is chiefly harvested from Upper Klamath Lake in southern Oregon and then freeze-dried and sold in capsules and other forms. The largest manufacturer is Cell Tech, which sells its "Super Blue-Green Algae" via thousands of special distributors.
Blue-green algae contain small amounts of protein, vitamins (including C, E, and folate), beta carotene, and some minerals. But unless you eat huge amounts of algae, they are a negligible source of nutrients. Like green plants, they are rich in chlorophyll, a pigment that enables them to turn sunlight into energy.
But chlorophyll is of no use to the human body. Prevents cancer and heart disease and boosts immunity. Treats or cures a host of ailments, including asthma, allergies, anxiety, depression, fatigue, hypoglycemia, digestive problems, and attention deficit disorder. Helps with weight loss, improves memory and mental ability, "detoxifies" the body.