The Noni plant and its fruit have been used in Polynesia for folkloric medicinal purposes for over 2,000 years, notes the Natural Standard. While scientific research has confirmed that noni contains antioxidant, immune-stimulating, and tumor-fighting properties, its effect on humans has not been studied, warns the National Institutes of Health. In particular, individuals should be wary of noni's effects on the liver, which are disputed between medical practitioners.
Drinking noni juice decreases laboratory-induced liver damage, notes the journal "Plant Foods and Human Nutrition". The March 2008 article entitled "Liver Protective Effects of Morinda citrifolia (Noni)" describes how researchers treated female rats with water-diluted noni juice before applying tetrachloride, an environmental pollutant known to cause liver cancer. In two experiments, group of rats receiving noni juice had diminished liver damage. Researchers concluded that the noni juice provided protection from extrinsic toxin exposure.
The organic compounds known as anthraquinones in noni juice can induce acute liver toxicity, cautions the World Journal of Gastroenterology. In the August 2005 article, entitled "Hepatotoxicity of NONI Juice: Report of Two Cases," researchers discuss how drinking noni juice over three weeks caused a 29-year-old male with prior liver toxicity to develop hepatic failure. After drinking noni juice for three weeks, a 62-year-old man with no previous liver toxicity developed acute hepatitis.
The quantity of anthraquinones in noni fruit is too small to have toxicological significance, concluded the "World Journal of Gastroenterology." The June 2006 study entitled "Noni Juice is Not Hepatotoxic" mirrored the European Union's 2006 conclusion that noni juice was safe for consumption and its adverse effects had not been scientifically proven. Moreover, human levels of anthraquinone reported in case studies were far lower than laboratory animals, who incurred no liver damage.