Stephen Barrett wrote on Quackwatch, "In my opinion, her advice is untrustworthy and is particularly dangerous to people with cancer".[49] Metabolic therapies – an umbrella term for diet- and enema-based "detoxification" regimes, such as the Gerson therapy, promoted to cure cancer and other disease. The Memorial Sloan-Kettering Cancer Center states: "Retrospective reviews of the Gerson, Kelley, and Contreras therapies show no evidence of efficacy."[44] Nieper therapy – a regimen devised by Hans Alfred Nieper (1928–1998) which was based on taking a variety of substances, including amygdalin and vitamins, and which Nieper claimed could treat a variety of serious ailments, including cancer.