Written by Helen Cooke, Helen Seers and the CAM-Cancer Consortium.
Updated April 29, 2016

Gerson therapy

Does it work?

Based on one methodologically flawed retrospective study and several case reports, there is no clear evidence that Gerson therapy is an effective treatment for people with cancer. A small ‘Best Case Series’ review concluded that both physical and psychological benefits, appeared to be offered by this regime, but these findings have not been replicated in any acceptable trials. No randomised controlled trials have been conducted on the Gerson Therapy. Attempts to evaluate the Gerson therapy as a whole are problematic due to the complexity of the treatment, time taken for its possible effectiveness and poor record keeping/tracking of previous patients by the Gerson Institute.6

Clinical trials

A five-year survival rate retrospective study of 153 cancer patients found higher survival rates in patients with melanoma, colorectal and ovarian cancers undergoing the Gerson regime than for patients undergoing other therapies.7 However, it should be noted this work was conducted by members of the Gerson Research Organisation and has been criticised as being seriously methodologically flawed.8 This research did not use the same matched control for each of their categories studied. Furthermore, it was not performed under tightly controlled conditions assessing the other therapies that the patients may have been receiving.

Case reports/series

Since the 1940s several attempts have been made to assess the efficacy of the Gerson therapy. In 1947 the NCI (National Cancer Institute) reviewed case studies of ten people from Gerson and found no evidence to support Gerson’s claims of the therapy being effective.9 The 50 cases presented in Gerson’s 1958 book10 were also reviewed by the NCI in 1959, however, it was concluded that the case histories were not presented in sufficient detail (for instance, verification of the tumour, previous treatment history) to be able to evaluate the clinical benefit of the therapy.11

A preliminary study conducted in 1983 tracked down 21 patients over a five-year period and found all but one (who was not cancer free) had died at the end of the study period.12 However, due to not obtaining detailed medical records at the start of this study this research is not very substantive.

In 1989, Reed et al. visited the Gerson clinic to evaluate the efficacy of the therapy on behalf of a British medical insurance company.13 Two investigations were conducted and presented in one paper. The first investigation concerned how patients responded to the therapy and the other was a psychological study of the patients at the clinic. For the first investigation, the Gerson clinic presented 149 cases to the researchers. Of the 149 only 27 cases were able to be assessed as they possessed independent documentation of their disease from a mainstream physician. The researchers concluded that there was little evidence for the Gerson therapy having an anti-tumour effect, instead finding only a very small amount of successful responses with three of the 27 cases showing a complete response and one patient with a stable disease result. The second study by Reed et al collected data from 15 patients concerning their psychological state while undergoing the therapy.13 The researchers found a marked enhancement of pain control and quality of life was enhanced. However, it must be noted that no firm conclusions can be drawn from this observational study due to the small number of participants.

A 2007 case study analysis of six people with cancer who followed the Gerson therapy concluded that some support, both physical and psychological, appeared to be offered by this regime.14 The analysis reported that some potential anti-cancer effects appeared to be present in the patients who undertook this regime. The patients also had an increased sense of hope and empowerment. The authors stated however that many cofactors may have influenced these findings; some of the patients were undergoing conventional treatment, some were also using other complementary approaches. The analysis was conducted using the 'Best Case Series' criteria developed by the National Cancer Institute.15

A 2010 overview of the Gerson regimen reported that case reviews by the National Cancer Institute (NCI) and the New York County Medical Society found no evidence of usefulness for the Gerson diet.16


Helen Cooke, Helen Seers, CAM-Cancer Consortium. Gerson therapy [online document]. http://www.cam-cancer.org/The-Summaries/Dietary-approaches/Gerson-therapy. April 29, 2016.

Document history

Assessed as up to date in April 2016 by Barbara Wider.

Assessed as up to date in January 2015 by Barbara Wider.
Assessed as up to date in August 2013 by Barbara Wider.
Most recent update and revision in September 2012 by Helen Cooke.
Fully revised and updated in August 2011 by Helen Cooke.
Fully revised and updated in November 2009 by Helen Cooke.
Summary first published in July 2005, authored by Helen Seers and Helen Cooke.


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