Sheep sorrel Rumex acetosella

World Distribution

The roots of Sheep sorrel herb (Rumex acetosella) were the key to the success of Rene Caisse’s Essiac therapy at the Bracebridge Cancer Clinic during the 1930’s. In addition to the active ingredients in the leaves and stems (including aloe-emodin), the roots contain three powerful anthraquinones, chrysophanol, emodin and physcion, plus the flavonoid (plant pigment) quercetin.

Rene Caisse preferred to harvest the herb herself and never talked about it except at the end of her life to her most trusted friend, Mary McPherson, who she had come to depend upon to help prepare the tea for her patients. Contrary to later claims, she never disclosed any details of her Essiac formula or related formulae to Dr. Charles Brusch at any time, as verified by the doctor himself on tape to Sheila Snow in January 1980 and again live on Elaine Alexander’s ‘Staying Alive’ radio show, January 19, 1986.  See Audio Files 118-121.

She never mentioned Sheep sorrel during radio interviews or to the press and referred to it in writing only to one person, Dr. C. Chester Stock, Vice President, and Director of the Walker Laboratory at the Sloane–Kettering Institute for Cancer Research (MSKCC)  New York, where he authorised six Essiac studies to be carried out over a two-year period during the mid 1970’s.  

The series of letters exchanged between her and Dr. Stock between 1973 – 1976 prove she trusted only someone as prestigious as Dr. Stock with the identity of the key plant in her remedy, revealed for the first time on an accompanying page included with her letter of March 27, 1974,  directed, ‘In confidence to Dr. C. Chester Stock of Sloan Kettering Institute for Cancer Research, from Rene M. Caisse McGaughey’: See Correspondence, Dr. C. Chester Stock and Rene Caisse McGaughey 1973-1976, No. 12.

‘The herb that will destroy a cancer (a malignant growth) is the dog-eared Sheep sorrel sometimes called Sourgrass. The entire plant must be used, picked in the spring before the seeds form, then dried and powdered…’  

April 2, 1974: ‘Since your first letter to me I have felt that you were the one person I could trust to prove my long years of work…’ 

April 4, 74: ‘I have the greatest confidence in you, Dr. Stock, and I do want to have you test my “Essiac” treatment for the sake of the many who suffer cancer in its many forms.  

May 10, 74: Last sentence in letter: ‘You can understand, I hope, why I hesitated to tell what I used. It really is so simple, I felt sure that no one would believe in it. In forty years, you are the only person who knows. I feel relieved to know that I found someone I could trust” 

May 74, undated: ‘It took years to find out the one herb that actually worked on the growth itself. The other herbs I used to purify the blood and throw off any infection thrown off by the malignant growth as it regressed.’ 

January 24, 1975, last paragraph: ‘The reason I offered to send you more material was because I know you cannot buy the entire plant. You can buy the crushed leaves, but they are no good alone. I found this out when I needed so much, when treating three to six hundred people afflicted with cancer every week for eight and a half years. I do know the whole plant is needed.’  

TRIAL TWO, APRIL 16, 1975, DURATION SIX WEEKS, REPORT POSITIVE, JUNE 1975: regressions were indicated in ‘sarcoma 180’ in treated mice after Rene Caisse had supplied newly prepared samples of dried Rumex acetosella as leaves, stems and roots.  

August 4, 1975 – letter, Rene Caisse to Dr. Stock:
‘I am very shocked at the way your people are using the materials I sent you. The way they are preparing it for injections is an absolute waste. They might as well inject sterile water… they are just using leaves and stems, leaving out the roots. They are a part of Essiac and to strain it through cheesecloth destroys it… You are the only person in the world that I have trusted completely, Doctor Stock, and I had such high hopes that even if I should pass on, it would be made available to suffering humanity (at least as a very beneficial treatment for cancer). 

June 14, 1976: ‘I thought about the way the lab had been preparing the material for the tests and why they were not getting better results. So, I read over their preparation and found that they were only using the leaves and stems, leaving out the roots which are very essential in the “Essiac” for treatments.’ 

Notice of termination of the trials were served by letter, August 25, 1976, Dr. Stock to Rene Caisse: stating his decision to keep the test capacity available for ‘materials from others who are satisfied with our testing procedures.’ 

In response to Sheila Snow Fraser’s letter of January 15, 1979, Dr. Stock provided her with copies of some of the letters in the MSKCC archive. He justified withholding others that Rene had written in anger, preferring they should not be made available as the language she employed was ‘not suitable for a lady’ in his view. See Correspondence – Stock, Dr. C.C./MSKCC 1973-1979