Herbal supplements and cancer

Herbal supplements as well as dietary supplements could cause cancer. According to recent research one in five cases of chemical-induced liver damage come from herbal and dietary supplements. Herbal remedies containing aristolochic acids (AA), a compound found in leafy, flowery vines called Aristolochia (or birthwort) and Asarum is the most potent carcinogen that have been linked to several types of cancer. Aristolochic Acid is a natural product of plants used in some weight loss supplements too. A study, published in Science Translational Medicine found that in 78 percent of liver cancer samples collected in Taiwan showed a distinctive mutation consistent with AA exposure. The research team looked at 98 samples of hepatocellular carcinoma, the most common type of liver cancer, and the most common cause of death in people with cirrhosis [1].  Also cancers of the upper urinary tract (renal pelvis and ureter) and bladder  have been reported among individuals who had kidney damage caused by the consumption of herbal products containing AA.

Aristolochic acid is absorbed from the gastrointestinal tract and distributed unchanged and/or in metabolized form throughout the body. The major activation pathway of AA involves reduction of the nitrogroup, and is catalysed by several human cytosolic and microsomal enzymes such as hepatic and renal cytosolic NAD(P)H:quinone oxidoreductase (NQO1), hepatic microsomal cytochrome P450 (CYP)1A2 and renal microsomal NADPH:CYP reductase – NQO1 being the most important [2]. During reductive activation, aristolochic acids form an electrophilic cyclic N-acylnitrenium ion that reacts with purine bases to form DNA adducts. These DNA adducts found in patients with liver, bladder and renal cancer, act as biomarker for exposure to AA.

AA has been officially banned in Europe since 2001 and in Singapore since 2004. Some herbs that contain AA have been banned in Taiwan since 2003, and in China, the use of some, but not all, AA-containing herbs in traditional medicine is restricted. But the United States Food and Drug Administration has issued strong  warnings about herbs containing AA. Food and Drug Administration (FDA) is advising consumers to immediately discontinue use of any botanical products containing aristolochic acid. These products may have been sold as "traditional medicines" or as ingredients in dietary supplements [3].

References:

1. http://www.iflscience.com/health-and-medicine/herbal-remedies-have-been-linked-to-liver-cancer-across-asia/
2. https://www.ncbi.nlm.nih.gov/books/NBK304331/
3. https://www.eurekalert.org/pub_releases/2017-10/dms-srh101717.php