Chlorella which is a type of algae contains a lot of nutrients and is very healthy for a person as long as they're not allergic to the Chlorella.
Chlorella is also a great source of several vitamins, minerals and antioxidants and can also help get toxins out of your body and improve cholesterol and blood sugar levels.
Some side affects that some people may experience from Chlorella are Diarrhea, Nausea, Gas (flatulence), Green discoloration of the stools and even Stomach cramping especially during the first few weeks of use.
And sensitivity to sunlight can also happen when taking Chlorella.
Also if a person has breathing problems or Asthma then the Chlorella can affect those peoples breathing problems and Asthma so I would ask your doctor before taking Chlorella if you have Asthma or other breathing problems to avoid any other harm.
Other than that Chlorella is pretty safe to take and provides a lot more health benefits.