Specifics relating to the development of cancer and disease mechanisms
BACKGROUND AND PURPOSE:
Vitamin D-related compounds can inhibit cancer cell growth, but the biologic mechanism of this inhibition remains to be determined. We investigated the possibility that these compounds interfere with the activity of insulin-like growth factors. Such activity can be suppressed or otherwise modulated by specific insulin-like growth factor-binding proteins.
The effects of successive administration, withdrawal and readministration of high protein diets (20% casein) on the promotional growth, remodeling and regrowth of aflatoxin B1-induced preneoplastic liver lesions (foci) were examined. Weanling male Fischer 344 rats were given 10 intragastric doses of aflatoxin B1 at a level of 250 micrograms/kg body weight over a 2-wk dosing period (initiation). The subsequent 12-wk period was subdivided into four feeding periods, each lasting 3 wk (promotion).
This study reports the effect of a vegetarian diet and dexamethasone administration on the hormone status of healthy Caucasian men and premenopausal women. A lower nocturnal release of prolactin and testosterone occurred in men fed a vegetarian diet, while in women, dexamethasone administration decreased the nocturnal release of prolactin and caused a greater decrease of plasma dehydroepiandrosterone (DHEA).
A cancerostatic effect of vegetarian diets is proposed on the basis of a selective alteration of the metabolic pathways of fatty acids in neoplastic cells. Most vegetables lack the enzyme 6-desaturase (6D), which converts linoleic to arachidonic acid. Human cells have 6D, and therefore humans do not need to eat the higher polyunsaturated fatty acids found in animal tissues. Many neoplastic cells have lost the activity of 6D. A vegetarian diet would deprive neoplastic cells of higher-chain fatty acids and inhibit the activity of 6D.
The study population consisted of male vegetarians (aged 28-50 years), who were recruited from the vegetarian cohort being followed by the Department of Epidemiology (German Cancer Research Center, Heidelberg, FRG), and the same number of age- and sex-matched controls from the personnel of the same center. Among the vitamins tested, only the level of carotene was significantly higher in vegetarians; the levels of vitamin A, K, and E were not elevated. Among the other blood parameters tested, only creatinine and glutamine-transferase levels were significantly lower in vegetarians.
We studied 27 postmenopausal women, 9 vegetarians, 10 omnivores, and 8 apparently healthy women with breast cancer (BC), four times during 1 y. Dietary intakes were recorded and plasma androgens and sex-hormone-binding globulin (SHBG) binding capacity were determined. Androstenedione (A), testosterone (T), free T (FT), and SHBG were higher in omnivores than in vegetarians. In multiple correlation analysis, intakes of protein and fat were positively correlated with A, T, and FT, whereas the intakes of carbohydrate, grain, total fiber, and grain fiber showed the opposite correlations.
Between September 1984 and June 1985, a total of 75 adolescent girls, 35 vegetarians residing in a Seventh-Day Adventist school and 40 nonvegetarians residing in a private non-Adventist boarding school, underwent measurement of their plasma hormone levels in the follicular and luteal phase of their menstrual cycles as well as dietary intake measured by 3-day food records, medical history, height, and weight.
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