Betacyanin is the redish to violet pigment found in beets.

Betacyanin causes red urine (beeturia) and feces in some people who are unable to break it down.

References

Ilnitskii AP, Iurchenko VA. Effect of fruit and vegetable juices on the changes in the production of carcinogenic N-nitroso compounds in human gastric juice. Vopr Pitan 1993 Jul-Sep;(4):44-6. Ishizuka S, Ito S, Onuma M, et al. Ingestion of sugar beet fiber enhances irradiation-induced aberrant crypt foci in the rat colon under an apoptosis-suppressed condition. Carcinogenesis 1999 Jun;20(6):1005-9. Ishizuka S, Tanaka S. Modulation of CD8+ intraepithelial lymphocyte distribution by dietary fiber in the rat large intestine. Exp Biol Med 2002 Dec;227(11):1017-21. Nagai T, Ishizuka S, Hara H, Aoyama Y. Dietary sugar beet fiber prevents the increase in aberrant crypt foci induced by gamma-irradiation in the colorectum of rats treated with an immunosuppressant. J Nutr 2000 Jul;130(7):1682-7.