National Cancer Institute

Expert-reviewed information summary about Gerson therapy as a treatment for people with cancer. Note: The information in this summary is no longer being updated and is provided for reference purposes only.

This PDQ cancer information summary for health professionals provides comprehensive, peer-reviewed, evidence-based information about the use of Gerson therapy in the treatment of people with cancer. It is intended as a resource to inform and assist clinicians who care for cancer patients. It does not provide formal guidelines or recommendations for making health care decisions.

This summary is reviewed regularly and updated as necessary by the PDQ Integrative, Alternative, and Complementary Therapies Editorial Board, which is editorially independent of the National Cancer Institute (NCI). The summary reflects an independent review of the literature and does not represent a policy statement of NCI or the National Institutes of Health (NIH).

Gerson Therapy


NOTE: The information in this summary is no longer being updated and is provided for reference purposes only.

This cancer information summary provides an overview of the Gerson therapy as a treatment for people with cancer. The summary includes a brief history of the development of the Gerson therapy; a review of laboratory, animal, and human studies; and possible side effects associated with the use of this treatment.

This summary contains the following key information:

  • The Gerson therapy is advocated by its supporters as a method of treating cancer patients based on changes in diet and nutrient intake.
  • An organic vegetarian diet plus nutritional and biological supplements, pancreatic enzymes, and coffee or other types of enemas are the main features of the Gerson therapy.
  • The regimen is intended to “detoxify” the body while building up the immune system and raising the level of potassium in cells.
  • The regimen is empirically based on observations made by Max Gerson, M.D., in his clinical practice and on his knowledge of research in cell biology at the time (1930s–1950s).
  • No results of laboratory or animal studies are reported in the scientific literature contained in the Medical Literature Analysis and Retrieval System Online database.
  • Few clinical studies of the Gerson therapy are found in the medical literature.

Many of the medical and scientific terms used in this summary are hypertext linked (at first use in each section) to the NCI Dictionary of Cancer Terms, which is oriented toward nonexperts. When a linked term is clicked, a definition will appear in a separate window.

Reference citations in some PDQ cancer information summaries may include links to external websites that are operated by individuals or organizations for the purpose of marketing or advocating the use of specific treatments or products. These reference citations are included for informational purposes only. Their inclusion should not be viewed as an endorsement of the content of websites, or of any treatment or product, by the PDQ Integrative, Alternative, and Complementary Therapies Editorial Board or the National Cancer Institute.

General Information

The Gerson therapy is a complex regimen advocated by its supporters to treat cancer and other degenerative diseases. It consists of a specialized diet to “detoxify” the body and rebuild the immune system, adding vitamin and mineral supplements to help in these processes. Coffee enemas are an essential part of the regimen. The therapy is named for its developer, Max Gerson, a German physician who emigrated to the United States and started a medical practice in New York City in 1938.

The Gerson therapy is rooted in the belief that cancer is a disease of the whole organism, the tumor being only a symptom of a diseased body. Gerson considered cancer to be an accumulation of several damaging factors that combine to cause the deterioration of the entire metabolic system. The goal of the Gerson therapy is to bring the body back to its normal metabolic state, or as near to this state as possible, and to keep the metabolism in natural equilibrium.

Gerson observed that cancer patients exhibited markedly degenerated organs, especially the liver, presumably caused by the clearing of toxic materials of an unknown type that the disease produced. He also noted that the situation became worse after chemotherapy, probably because of more toxic products entering the bloodstream. Gerson’s regimen focused on helping the liver rid the body of toxic substances while restoring and maintaining healthy liver function.

According to Gerson, during the detoxification process that results from the Gerson diet, the liver becomes progressively overburdened as the body rids itself of toxic substances formed by the breakdown of cancer cells. Coffee enemas, pancreatic enzymes, and crude liver extract are used to help the liver deal with the burden of removing toxic substances.

Total control of everything that enters and leaves the body is the governing principle of the Gerson regimen. Its three main components are strict diet, nutritional supplements, and regular enemas.

The diet is strictly vegetarian for at least 6 weeks and consists of specific fruits and vegetables, eaten either raw or stewed in their own juices. No animal protein is allowed. Some whole grains such as oatmeal are included. Flaxseed oil is allowed only because it aids in the body’s use of vitamin A. No other fat such as cooking oil and no salt or spices of any kind are allowed. A glass of freshly prepared juice from vegetables and fruits must be consumed every hour for 13 hours throughout the day. The vegetables and fruits used on the diet are very high in potassium and very low in sodium.

Food preparation is also controlled. Food may be prepared only in cast-iron pots and pans; no aluminum cookware is allowed. Juices must be prepared using a specific type of juicer that crushes the fruit or vegetable rather than grinding it into pulp. Gerson advocated organically produced food, with all fruits, vegetables, and grains grown and raised in soil free of pesticides and contaminants and enriched only with natural fertilizers.

The protein and dairy restriction may be lifted to include buttermilk; however, this restriction may continue through the entire course of the therapy, depending on the individual patient. Some changes in the original diet have occurred over time, but the initiation phase of the diet has always been a vegetarian diet.

Taking specific vitamin and mineral supplements plus pancreatic enzymes is the second component of the regimen. Although there have been additions and substitutions to the basic list of supplements, there have been few changes since the 1940s. The typical range of supplements includes the following:

The potassium solution (potassium dissolved in water) is to help increase the ratio of potassium to sodium in the cells. Lugol’s solution, which consists of 5 g of iodine and 10 g of potassium iodide dissolved in water, is given to increase the body’s metabolic rate. The potassium solution and Lugol’s solution are both added to the hourly juice intake.

Originally, Gerson thought that using crude liver extract and juice (made by processing fresh calf and veal livers) would help maintain liver function. The extract and juice were given to patients via injection with the vitamin B12. In 1989, the use of injectable crude liver extract was banned by the U.S. Food and Drug Administration because it was found to be contaminated with . Desiccated liver capsules replaced the crude extract, but this has now been replaced by coenzyme Q10. As mentioned above, flaxseed oil is used to help the body utilize vitamin A. Pancreatic enzymes are given to assist in the digestion and the elimination of the breakdown products in the colon.

Coffee (or chamomile) enemas are the third component of the Gerson therapy. Coffee enemas supposedly dilate the bile duct in the liver, thereby allowing the liver to release the breakdown products more easily and speed their removal to the intestine. At the beginning of therapy, a patient may take four or more coffee enemas per day. Literature suggests that coffee enemas help relieve the pain associated with gastrointestinal cancers; however, there is only anecdotal evidence to suggest that the enemas actually dilate the bile ducts.

Central to the therapy is an abundance of potassium and the lack of sodium. Gerson had observed that as soon as his cancer patients started on the diet regimen, they released large amounts of sodium in their urine. He noticed that cells in the patients’ bodies that had been bloated with fluid started to shrink as the fluid was released. After studying the research in cancer cell biology available to him at the time and noting the ratio of potassium to sodium in cancer cells versus healthy cells, he deduced that the reason for this sodium excretion was that the diet regimen was correcting generalized tissue damage caused by excess sodium. Healthy cells had a high ratio of potassium to sodium; diseased cells had a low ratio of potassium to sodium or an abundance of sodium.

The implications of this observation led Gerson to believe that part of the process of recovery from cancer was the replacement of excess sodium by potassium in damaged tissues. This belief is the theoretical basis for Gerson’s choice of high-potassium, low-sodium fruits and vegetables in his prescribed diet: a high intake of potassium was needed to restore a normal ratio of potassium to sodium in the cell.

The Gerson therapy is the basis for other CAM therapies that include cleansing enemas or special diets as part of their regimens, most notably the Gonzalez regimen. (Refer to the PDQ summary on the Gonzalez Regimen for more information.)


Max Gerson immigrated to the United States from Germany. In 1938, after passing the New York state medical board examinations, he started a practice in New York City. While in Germany, Gerson had suffered from severe migraine headaches and developed a vegetarian diet as a way to cure his migraines. The diet was based on his study of the history of medicine and his respect for the writings of Paracelsus (1490–1541), who said that diet must be the basis of medical therapy; however, Gerson noted that diet is only one part of a treatment regimen. The special diet cured his migraines, and after seeing its success in one of his patients suffering from lupus vulgaris, he prescribed the diet for others suffering from the same disease. He conducted a successful clinical trial in Germany using the vegetarian diet. His most noted patient was the wife of Albert Schweitzer, M.D., whom he reported curing. The accolades he received from Dr. Schweitzer may have persuaded the medical community to seriously consider the Gerson therapy and perhaps led to Gerson’s 1946 appearance with five of his patients before a congressional committee considering a bill to increase funding for cancer research.

When Gerson began prescribing his regimen for patients, he did not consider his therapy a cure for cancer. At that time he wrote that there was no conclusive evidence from his work that cancer was influenced by diet; however, he did think that diet was a useful supportive measure. In 1958, after treating patients with his regimen for more than 15 years, Gerson published his complete theory, including the results of 50 cases. He started referring to his regimen as an “effective treatment for cancer, even in advanced cases.”

The practice of changing diet or fasting to cure or ameliorate the effects of disease has a long history, as does the practice of giving enemas to flush the body, thus keeping the body clear of toxins. There are no reported results of clinical trials examining the efficacy of either of these practices in the treatment of cancer or how these practices would affect a treatment. Evolving evidence supports the idea that a plant-based diet plays a role in cancer prevention.

Gerson theorized that the use of pancreatic enzymes would reduce demands on the liver and pancreas, already in a weakened state, to manufacture the enzymes necessary to convert food into usable nutrients; this would help stabilize the nutritional needs of the body while it undergoes the detoxification process. Gerson’s therapy was widely considered impossible because it was thought that pancreatic enzymes were reduced to their components in the intestinal tract. However, it has been reported that these enzymes are not broken down but are released into the bloodstream and used again in the digestive process.

Controversy about the efficacy of the Gerson therapy continued throughout Gerson’s life. In 1946 and 1949, two articles in the Journal of the American Medical Association concluded that the treatment was of no value. The National Cancer Institute (NCI) reviewed Gerson’s data from ten case histories in 1947 and 50 case histories in 1959. NCI concluded that in most cases, basic criteria for evaluating clinical benefit were not met. NCI concluded that the data demonstrated no benefit. In 1972, the American Cancer Society (ACS) published a statement summarizing the negative assessments of Gerson’s treatment. Another statement published by ACS in 1991 concerned various “metabolic therapies” (defined as treatments that depend on changing metabolism through diet, enemas, and supplements given at clinics in Tijuana, Mexico) and reemphasized the lack of scientific evidence on the efficacy of the Gerson regimen.

Gerson died in 1959, leaving behind no systematic way to continue offering his treatment. His malpractice insurance had been canceled in 1953, and in 1958 he was suspended for 2 years from the New York County Medical Society. In 1977, his daughter, Charlotte Gerson Straus, who had continued to lecture widely about the Gerson therapy, cofounded the Gerson Institute with Norman Fritz. Located in San Diego, the Gerson Institute does not own or operate treatment facilities but maintains a licensing program for treatment centers such as the Centro Hospitalario Internacional Pacifico and Mexico’s Center for Integrative Medicine and the Gerson Hospital (CHIPSA) in Baja California, Mexico. CHIPSA refers to Max Gerson as the founder of “immunonutrition,” their term for Gerson’s idea of cleansing the body while building up the immune system through diet and supplementation.

Laboratory/Animal/Preclinical Studies

There are no studies in animal models of the Gerson diet in the scientific literature.

Human/Clinical Studies

Gerson’s book and articles in English are primarily reports of the details of the Gerson regimen, supplemented with case reports of patients seen in his clinical practice. His book presents an extended discourse on the empirical and scientific foundation for his treatment regimen and an expansive description of the treatment and diet followed by 50 patients selected from 30 years of clinical practice. Gerson’s published cases encompass a variety of cancer types. The reports are extended case notes, with occasional x-rays of the patients over time. Although some attempt at follow-up is made, it is not systematic and consists chiefly of anecdotal reports and conversations with patients by mail or phone.

A preliminary study conducted between 1983 and 1984 attempted to collect any available retrospective data on three nonallopathic treatments offered in clinics in Tijuana, Mexico: Gerson, Hoxsey, and Contreras. The authors did not have access to medical records and relied on patient interviews for all information. The self-reporting was incomplete and inconsistent, lacking precise information in areas such as how far the disease had advanced. In the Gerson segment, only 18 of the 38 patients stayed in the study for 5 years or until they died; their mean survival was 9 months from the beginning of the study. The other 20 patients were lost to follow-up. At 5 years, 17 of the 18 had died, and one patient with advanced non-Hodgkin lymphoma was alive but not disease free. Overall, this study did not offer meaningful data to support the clinical efficacy of the approaches studied.

A 1990 noncontrolled, self-selected, matched-pairs study conducted in Austria used a diet regimen based on the Gerson therapy to evaluate diet as an adjuvant to surgery. This diet was ovolactovegetarian. The Gerson regimen is basically strictly vegetarian (no eggs or milk) and does not introduce food other than buttermilk until 6 or 8 weeks into the regimen, if at all, depending on the patient.

Two groups of patients who had undergone surgery—18 patients with colorectal cancer with metastases to the liver and 38 with breast cancer—were treated. Each of the two groups was divided into a diet group and a nondiet group. All patients continued with whatever prescribed conventional regimen was required after their surgery. Results in the matched pairs with colorectal cancer showed an increased survival time in three of the nine patients in the diet group (28.6 months) as compared with four of the nine patients (16.2 months) in the nondiet group. In the breast cancer matched pairs, side effects of chemotherapy and pain and pleural effusion were lower in the diet group. No statistically significant information was generated in this small number of patients; however, the authors stated that the diet regimen appeared to have beneficial effects that required further study.

The Gerson Research Organization published a retrospective survival analysis of their melanoma patients treated with the Gerson approach, which was compared with published survival data according to stage. The analysis showed a survival advantage for melanoma patients with stage IIIA disease and stage IV disease with no visceral metastases, who were treated with the Gerson approach. However, there has been no report of a prospective clinical trial confirming the findings of this retrospective analysis.

The study looked at records of 153 patients with stage I–IV melanoma treated with the Gerson diet. Of the 14 stage I–II patients, all were disease-free at 17 years posttreatment; however, this number was too small for a statistical comparison with other cohorts. For stage III patients, the 5-year survival rate was 71% compared with rates of 27% to 42% reported in the literature. The stage IV patients had the largest survival advantage. The 5-year survival rate for these 18 patients was 39%, compared with 6% in the published literature. The analysis did not include 53 patients who were lost to follow-up, which could have influenced the survival comparisons.

A small best-case series suggests that the evidence presented supports the development and conduct of a more definite clinical study on the Gerson regimen.

No conclusions about the effectiveness of the Gerson therapy, either as an adjuvant to other cancer therapies or as a cure, can be drawn from any of the studies reported above.

Adverse Effects

Case reports of adverse events associated with coffee enemas raise concern about their use. Three deaths that seem related to coffee enemas have been reported in the literature. group D and were cultured from stool and blood of one patient who died shortly after treatment at the Gerson Institute clinic. This death could not be directly linked to the practice of coffee enemas because more tests could not be performed.

Case reports of two more deaths following treatment at the Gerson Institute were both attributed to electrolyte imbalance after autopsies were performed showing no active inflammation of the colon.

A third case report of electrolyte imbalance that did not result in death describes a patient who developed hyperkalemia while undergoing Gerson therapy. No other reports of adverse effects have been identified.

Summary of the Evidence for Gerson Therapy

To assist readers in evaluating the results of human studies of integrative, alternative, and complementary therapies for cancer, the strength of the evidence (i.e., the “levels of evidence”) associated with each type of treatment is provided whenever possible. To qualify for a level of evidence analysis, a study must:

Evidence from studies that do not meet these requirements is considered extremely weak. In addition to scoring individual studies, an overall level of evidence assessment is usually made.

Because no prospective, controlled study of the use of the Gerson therapy in cancer patients has been reported in a peer-reviewed scientific journal, no level of evidence analysis is possible for this approach. The data that are available are not sufficient to warrant claims that the Gerson therapy is effective as an adjuvant to other cancer therapies or as a cure. At this time, the use of the Gerson therapy in the treatment of cancer patients cannot be recommended outside the context of well-designed clinical trials.

Separate levels of evidence scores are assigned to qualifying human studies on the basis of statistical strength of the study design and scientific strength of the treatment outcomes (i.e., endpoints) measured. The resulting two scores are then combined to produce an overall score. For additional information about levels of evidence analysis, refer to Levels of Evidence for Human Studies of Integrative, Alternative, and Complementary Therapies.

Changes to This Summary (04/11/2015)

The PDQ cancer information summaries are reviewed regularly and updated as new information becomes available. This section describes the latest changes made to this summary as of the date above.

Editorial changes were made to this summary.

This summary is written and maintained by the PDQ Integrative, Alternative, and Complementary Therapies Editorial Board, which is editorially independent of NCI. The summary reflects an independent review of the literature and does not represent a policy statement of NCI or NIH. More information about summary policies and the role of the PDQ Editorial Boards in maintaining the PDQ summaries can be found on the About This PDQ Summary and PDQ® - NCI's Comprehensive Cancer Database pages.

About This PDQ Summary

Purpose of This Summary

This PDQ cancer information summary for health professionals provides comprehensive, peer-reviewed, evidence-based information about the use of Gerson therapy in the treatment of people with cancer. It is intended as a resource to inform and assist clinicians who care for cancer patients. It does not provide formal guidelines or recommendations for making health care decisions.

Reviewers and Updates

This summary is reviewed regularly and updated as necessary by the PDQ Integrative, Alternative, and Complementary Therapies Editorial Board, which is editorially independent of the National Cancer Institute (NCI). The summary reflects an independent review of the literature and does not represent a policy statement of NCI or the National Institutes of Health (NIH).

Board members review recently published articles each month to determine whether an article should:

  • be discussed at a meeting,
  • be cited with text, or
  • replace or update an existing article that is already cited.

Changes to the summaries are made through a consensus process in which Board members evaluate the strength of the evidence in the published articles and determine how the article should be included in the summary.

The lead reviewer for Gerson Therapy is:

  • Patrick J. Mansky, MD (FMH Regional Cancer Therapy Center)

Any comments or questions about the summary content should be submitted to through the NCI website's Email Us. Do not contact the individual Board Members with questions or comments about the summaries. Board members will not respond to individual inquiries.

Levels of Evidence

Some of the reference citations in this summary are accompanied by a level-of-evidence designation. These designations are intended to help readers assess the strength of the evidence supporting the use of specific interventions or approaches. The PDQ Integrative, Alternative, and Complementary Therapies Editorial Board uses a formal evidence ranking system in developing its level-of-evidence designations.

Permission to Use This Summary

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The preferred citation for this PDQ summary is:

National Cancer Institute: PDQ® Gerson Therapy. Bethesda, MD: National Cancer Institute. Date last modified . Available at: Accessed .

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