WebMD says that the safety of consuming humic acid is unknown. Some studies have linked humic acid consumption to diseases of the joints, circulatory system and thyroid. WebMD warns people with autoimmune diseases not to take humic acid because it can worsen symptoms.
Dr. Wayne Kussow, writing for Horticulture Update, explains that humic acid is an end-product of organic matter decomposition. Humic acid is prepared by treating fully decomposed organic materials with sodium hydroxide and then adding acid until a black solid forms. The black solid has been given the name humic acid. It consists of carbon, some hydrogen and about 4 percent nitrogen.