Spirulina is a blue-green algae that may provide a source of dietary protein, B-vitamins, and iron. It may also be used for weight loss, attention deficit-hyperactivity disorder (ADHD), hayfever, diabetes, stress, fatigue, anxiety, depression, and premenstrual syndrome (PMS) and other women’s health issues. Spirulina may also be effective for precancerous growths inside the mouth, boosting the immune system, improving memory, increasing energy and metabolism, lowering cholesterol, preventing heart disease, healing wounds, and improving digestion and bowel health.The spirulina species of blue-green algae contains the chemical phenylalanine, which enhances mood and thinking. This might make phenylketonuria worse. Avoid Spirulina species blue-green algae products if you have phenylketonuria.