While it is safe for most people, some people can be allergic to red seaweed, which agar is derived from. It should also be paired with plenty of water as agar expands and may cause blockages in the esophagus or intestine. People with a history of colon cancer should discuss with their doctor before using agar, as certain fibers, including agar, have been linked to tumor growth (although the research is limited). It has many health benefits as well, such as being high in fiber and containing magnesium, calcium, manganese, folate, calcium, and iron. It may promote digestive health, and support weight loss among other benefits due to its minerals and vitamins.