It sounds reasonable enough.  According to the Gerson Institute the Gerson diet:

is naturally high in vitamins, minerals, enzymes, micro-nutrients, extremely low in sodium and fats, and rich in fluids.

The following is a typical daily diet for a Gerson patient on the full therapy regimen:

• Thirteen glasses of fresh, raw carrot/apple and green-leaf juices prepared hourly from fresh, organic fruits and vegetables.
• Three full vegetarian meals, freshly prepared from organically grown fruits, vegetables and whole grains. A typical meal will include salad, cooked vegetables, baked potatoes, vegetable soup and juice.
• Fresh fruit and fresh fruit dessert available at all hours for snacking, in addition to the regular diet.

Then things get confusing.  Reading about the Gerson Therapy is like my first weeks as a judicial clerk for a federal judge, where I could still be swayed by whichever argument I was reading.  Witness the Gerson Institute’s common-sensical explanation:

Throughout our lives our bodies are being filled with a variety of disease and cancer causing pollutants. These toxins reach us through the air we breathe, the food we eat, the medicines we take and the water we drink. As more of these poisons are used every day and cancer rates continue to climb, being able to turn to a proven, natural, detoxifying treatment like the Gerson Therapy is not only reassuring, but necessary.

The Gerson Therapy is a powerful, natural treatment that boosts your body’s own immune system to heal cancer, arthritis, heart disease, allergies, and many other degenerative diseases. One aspect of the Gerson Therapy that sets it apart from most other treatment methods is its all-encompassing nature. . . . [T]hirteen fresh, organic juices are consumed every day, providing your body with a superdose of enzymes, minerals and nutrients . . . break down diseased tissue in the body, while enemas aid in eliminating the lifelong buildup of toxins from the liver.

With its whole-body approach to healing, the Gerson Therapy naturally reactivates your body’s magnificent ability to heal itself – with no damaging side-effects. Over 200 articles in respected medical literature, and thousands of people cured of their “incurable” diseases document the Gerson Therapy’s effectiveness. The Gerson Therapy is one of the few treatments to have a 60 year history of success.

The Institute goes on to add that “it is rare to find cancer, arthritis, or other degenerative diseases in cultures considered ‘primitive’ by Western civilization. Is it because of diet? The fact that degenerative diseases appear in these cultures only when modern packaged foods and additives are introduced would certainly support that idea.” Gerson’s solution:  “Stay close to nature and its eternal laws will protect you.”

The Gerson Therapy seeks to regenerate the body to health, supporting each important metabolic requirement by flooding the body with nutrients from almost 20 pounds of organically grown fruits and vegetables daily. Most is used to make fresh raw juice, one glass every hour, 13 times per day. Raw and cooked solid foods are generously consumed. Oxygenation is usually more than doubled, as oxygen deficiency in the blood contributes to many degenerative diseases. The metabolism is also stimulated through the addition of thyroid, potassium and other supplements, and by avoiding heavy animal fats, excess protein, sodium and other toxins.

Degenerative diseases render the body increasingly unable to excrete waste materials adequately, commonly resulting in liver and kidney failure. To prevent this, the Gerson Therapy uses intensive detoxification to eliminate wastes, regenerate the liver, reactivate the immune system and restore the body’s essential defenses – enzyme, mineral and hormone systems. With generous, high-quality nutrition, increased oxygen availability, detoxification, and improved metabolism, the cells – and the body – can regenerate, become healthy and prevent future illness.

According to critics, however, the evidence for the efficacy of the Gerson Therapy is lacking.  While the Institute cites “peer-reviewed” studies, critics claims Gerson’s people (Gerson being deceased half a century ago) haven’t provided any objective, peer-reviewed evidence for its efficacy, and Wikipedia cites numerous authorities who refuse to endorse the therapy, and even claim evidence of harm. So which is it?

Peer-Reviewed Studies:  Gerson’s Side

I’m not able to evaluate the “peer-reviewed” studies the Institute cites.  Most, though, are around sixty years old, and many of them pre-date the diet’s use on cancer specifically (first uses were on migraines and tuberculosis), with the latest study in 1978.  In the current climate, so favorable now to raw and whole foods, the lack of any studies since 1978 is a red flag.

I also see in the Institute’s explanations a certain anxiety in the war of propaganda apparently being waged: “No treatment works for everyone, every time. Anyone who tells you otherwise is not giving you the facts. . . . In most cases your trusted family physician only has knowledge of conventional treatments, and is either unaware of, or even hostile toward alternative options.” They sound defensive, which does not give me confidence. On the other hand, some proponents of the Gerson diet say they are battling far better funded pharma companies and doctors who have an economic interest in remaining indispensable. But is that enough to explain even the Institute’s own apparent failures to cite evidence supporting their claims?

Peer-Reviewed Studies:  The Critics

The American Cancer Society (ACS) – which I do not assume is without economic and other bias, says:

There have been no well-controlled studies published in the available medical literature that show the Gerson therapy is effective in treating cancer.

In a recent review of the medical literature, researchers from the University of Texas MD Anderson Cancer Center identified 7 human studies of Gerson therapy that have been published or presented at medical conferences. None of them were randomized controlled studies. One study was a retrospective review conducted by the Gerson Research Organization. They reported that survival rates were higher than would normally be expected for patients with melanoma, colorectal cancer and ovarian cancer who were treated with surgery and Gerson therapy, but they did not provide statistics to support the results. Other studies have been small, had inconclusive results, or have been plagued by other problems (such as a large percentage of patients not completing the study), making it impossible to draw firm conclusions about the effectiveness of treatment.

Quack Watch reviews the Institute’s claims in more seemingly devastating detail, saying the Institute’s claims are typical of several “Typical Misrepresentations”:

Proponents of questionable methods typically claim that marketplace demand and testimonials from satisfied customers are proof that their remedies work. However, proponents almost never keep score or reveal what percentage of their cases end in failure. Cancer cures attributed to questionable methods usually fall into one or more of five categories:

• The patient never had cancer.
• A cancer was cured or put into remission by proven therapy, but questionable therapy was also used and erroneously credited for the beneficial result
• The cancer is progressing but is erroneously represented as slowed or cured.
• The patient has died as a result of the cancer (or is lost to follow-up) but is represented as cured.
• The patient had a spontaneous remission (very rare) or slow-growing cancer that is publicized as a cure.

I know enough about statistics and the scientific method to find these critiques worth a pause.  If the critics are correct, the failure to produce any evidence of effectiveness over six or more decades is a serious one. An even-handed review by the seemingly more sympathetic (and Europe-based) Complementary and Alternative Medicine for Cancer (CAM-Cancer) also could not find support for the Institute’s claims, summarizing the matter thus:

Overall, the treatment has not been found to be effective as a cure for cancer. However, 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.

So What?

Does it matter if the method isn’t effective at curing cancer?  Only if (1) it precludes using or slows the efficacy of other methods or (2) it’s actively harmful.

My understanding is that Mom doesn’t intend to use the Gerson diet in lieu of any effective therapy.  Chemotherapy, for instance, is not effective on lung cancer like hers. So it may not matter at all that the Gerson Institute does not recommend the use of chemotherapy with its diet (on grounds “the chemotherapy is seen as a poison in the body, and during detoxification the body would find difficulty in dealing with the level of toxins” – see CAM-Cancer).

Can the Gerson diet be harmful?  Apparently it can, according to the critics and CAM-Cancer:

Gerson therapy can lead to several significant health problems. Serious illness and death have occurred as a direct result of some portions of the treatment, including severe electrolyte imbalances. Continued use of enemas may weaken the colon’s normal function, causing or worsening constipation and colitis. Other complications have included dehydration, serious infections and severe bleeding.

The therapy may be especially hazardous to pregnant or breast-feeding women.

Coffee enemas have contributed to the deaths of at least three people in the United States. Coffee enemas “can cause colitis (inflammation of the bowel), fluid and electrolyte imbalances, and in some cases septicaemia.” The recommended diet may not be nutritionally adequate. The diet has been blamed for the deaths of patients who substituted it for standard medical care.

Relying on the therapy alone while avoiding or delaying conventional medical care for cancer has serious health consequences.

(Citations omitted; see Wikipedia).

How can we prevent these negative effects, Mom, while still getting the undeniable benefits of whole, raw food?