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SECOND INTERNATIONAL SYMPOSIUM
ON THE ROLE OF SOY
IN PREVENTING AND TREATING CHRONIC DISEASE

September 15-18, 1996
Brussells, Belgium

SCIENTIFIC PROGRAM
(Oral Abstracts)

Soy and Cancer
Animal studies

Prevention of Precancerous Colonic Lesions in Rats by Soy Flakes, Soy Flour, Genistein and Calcium.
M.R. Bennink, D. Thiagarajan, L.D. Bourquin and A. Kavas.
Michigan State University, East Lansing, MI 48824-1224, USA.

Aberrant Crypt Foci (ACF) represent the precursor or pre-neoplastic lesions of colon cancer developing prior to the adenoma-to-carcinoma sequence. Quantitation of ACF is frequently used for assessing chemo-preventive potential of anti-carcinogenic compounds. A study with 117 rats was designed to investigate the chemo-preventive abilities of different soy products on colon carcinogenesis. Colon cancer was initiated in the rats by injecting 15mg/kg bw azoxymethane subcutaeneously at 21 and 28 days of age. At 35 days of age, the rats were placed on the dietary treatments: soy concentrate (very low in isoflavone content) as the control diet, full fat soy flakes, de-fatted soy flour, genistein (150 ppm), calcium, and a low-fiber diet for a period of twelve weeks. At the end of this period, the animals were sacrificed, entire colons were removed and the number of aberrant crypts per foci and the total number of aberrant crypt foci were counted. The results are as follows:

Treatment Avg. Body Weight (g) Avg. ACF # of Tumors

Soy Concentrate 237 132 a 3
Soy Flakes 216 97 b 1
Soy Flour 229 87 bc 0
Genistein 257 77 cd 0
Low-fiber diet 221 122 a 5
Calcium 264 70 d 0

There was a 40% reduction of ACF in the genistein fed group and 35% reduction of ACF in the soy flour fed group when compared to the soy concentrate fed group. Calcium and genistein have been shown to be effective in decreasing pre-cancerous lesions. Results from this study verify the same. Both soy flakes and soy flour reduced these pre-cancerous lesions and soy flour was statistically as effective as genistein in reducing the early stages of colon cancer.
(This study was supported by the Michigan Soybean Promotion Committee.)

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