Effect of dietary protein

Greger, J.L. 1989. Effect of dietary protein and minerals on calcium and zinc utilization. Crit. Rev. Food Sci. Nutr. 28 249-271. 

These data about the effect of dietary protein and calcium loss are consistent with epidemiological evidence linking diet and bone calcium loss. Walker, et al. (6) reported fracture rates ten times greater among white South Africans eating a meat-rich European type diet than among the local Bantu who consumed a vegetarian diet. 

Effect of Dietary Protein, Calcium, and Phosphorus on Calcium Metabolism in Humans... 

Effect of Dietary Protein On Skeletal Integrity in Young Rats... 

Sirtori, C.R., Galli, G., Lovati, M.R., CXarrara, P., Bosisio, E. and Kienle, M.G. (1998). Effects of dietary proteins on regulation of liver lipoprotein receptors in rats, J. Clin. Nutr., 114, 1493-1500. 

Weatherholtz WM, Campbell TC, Webb RE. 1969. Effect of dietary protein levels on the toxicity and metabolism of heptachlor. J Nutr 98 90-94. 

Klahr S, Levey AS, Beck GJ, Caggiula AW, Hunsicker L, Kusek HW et al. The effects of dietary protein restriction and blood-pressure control on the progression of chronic renal disease. Modification of diet in Renal Disease Study Group. N Engl J Med 1994 330 877-84. 

The effect of dietary protein on diazinon toxicity was evaluated in a study with male albino Wistar rats. The study concluded that a purified protein test diet (with 26% casein and 59% cornstarch) did not significantly alter the LD50 value (415 mg/kg) for diazinon for this species. However, a low protein purified test diet (3.5% casein, 82% cornstarch), lowered the LD50 to 215 mg/kg. In addition, this study found that diazinon samples that were time-of-manufacture stabilized (to prevent spontaneous degradation to more toxic monothiotetraethyl pyrophosphate) were less toxic (LD50 value = 466 mg/kg) than samples stabilized after manufacture (LD50 value = 271 mg/kg) (Boyd and Carsky 1969). A subsequent study... 

Huff, M.W. and Carroll, K.K. 1980. Effects of dietary protein on turnover, oxidation, and absorption of cholesterol, and on steroid excretion in rabbits. J. Lipid Res. 21, 546-558. 

Schal C., Chiang A-S., Burns E. L., Gadot M. and Cooper R. A. (1993). Role of the brain in juvenile hormone synthesis and oocyte development effects of dietary protein in the cockroach Blattella germanica (L.). J. Insect Physiol. 39, 303-313. 

Figure 1. The effect of dietary protein levels on various parameters associated with animal growth and xenobiotic metabolism. Rats were fed semifurified diets consisting of either 5%, 20%, or 30% casein as the protein source for 14-days. Data is expressed as a percent of the 20% control diet.

Epidemiological studies show that dietary fat and protein are most frequently correlated with colon cancer incidence in man (10-14). A number of studies in laboratory animals suggest that dietary fat enhances colon tumor incidence (15) although others have failed to show such enhancement (16). Summarized in this communication are animal experiments conducted by our laboratory to examine the effects of dietary protein on DMH induced carcinogenesis, mutagenesis, and toxicity. 

The mechanism whereby dietary protein influences DMH carcinogenesis is unknown. An attractive hypothesis concerning the effects of dietary protein on DMH metabolism is discussed later in this manuscript. Another factor which may contribute to tumor growth promotion in the intestine is a doubling of fecal crude lipid excretion which we observed in mice as dietary protein was increased from 10 to 40% of the diet (19). The association between... 

The next series of experiments were by Kari et al. (28) who examined the effect of dietary protein upon the activation of DMH to its mutagenic and, presumably, carcinogenic metabolites in mice. A combination of in vivo and in vitro assays were employed to assess the influence of dietary protein concentration on the production of mutagenic products from DMH, azoxymethane (AOM), and methylazoxy-methanol (MAM) (Figure 1). 

Figure 2. Effect of dietary protein concentration on cumulative expiration of [14C]AM ( o, ) and 1X02 ( a, a). Eight male weanling mice adapted for 3 days to the control diet were randomly divided into 2 groups Group 1, fed 2.5% casein (----) ...

Table IV. Effect of dietary protein concentration on host mediated mutagenicity of dimethylhydrazine (DMH), azoxy-methane (AOM) and methylazoxymethanol (MAll) in C57BL/6 x C3HF1 male mice...

Table V. Effect of dietary protein concentration distribution...

The Effects of Dietary Protein Concentration on Dietary DMH Toxicity in Mice... 

Our most recent studies examined the effects of dietary protein on the chronic toxicity resulting from feeding DMH in the diet. After a series of preliminary studies, B C F male mice were fed DMH for 5 months at the following dietary concentrations . 015,. 030, and. 045 mg/kg of diet. The diets were based upon the AIN-76 recommendations and contained soybean protein at 10 or 40% by weight. Five to 8 week old males were used. There were 25 mice per group. The data presented are preliminary and a complete description of these studies will appear elsewhere (Visek et al., to be published). 

Our laboratory has completed a series of studies designed to evaluate the simultaneous effects of dietary protein and fat on 7,12-dimethylbenz(a)anthracene (DMBA)-induced breast cancer in rats. Sprague-Dawley female rats were assigned to nine diets in a 3 x 3 factorial arrangement with protein (casein) at 8, 16, and 32% of kcals and fat (corn oil) at 12, 24, and 48% of kcals. As fat content was increased, all nutrients other than carbohydrate were adjusted to remain constant with respect to calories. Forty rats were assigned to each diet for each of three experiments (Figure 1) to examine initiation, promotion, and the combined phases of chemically-induced carcinogenesis. 

---