Dietary studies, design

In conclusion, phytic acid forms soluble complexes with Ca2+ at intestinal pH under a variety of conditions and fails to inhibit Ca2 bioavailability to mice in our experimental system. Despite the hazard in direct extrapolation of results obtained with animals kept on a well-defined dietary regimen to humans consuming a complex diet, many elements of which affect Ca2+ bioavailability, our data demonstrate the need for a reevaluation of the putative antinutritional properties of dietary phytate. Our further contention that adequate levels of dietary phytate may actually be beneficial due to its food preserving properties and its protection against colonic cancer will warrant a prospective epidemiological human study designed to assess the longterm effects of dietary phytate on mineral bioavailability and inflammatory bowel diseases. 

Although much attention has been directed toward the relationship between calcium intake and osteoporosis, little consideration has been given to the possible influence of dietary phosphorus on the development of this disease in either man or animals. In a study designed to determine the optimal concentration of calcium and phosphorus in the diet of adult mice, aging animals were found to undergo a greater loss of bone when the Ca/P ratio was 1 1 than... 

Two additional rat studies designed to investigate the reproductive effects of di-w-octylphthalatc exposure provide another observation on the hepatic effects of di-w-octylphthalate. Contrary to what is observed with di(2-ethylhexyl)phthalate, the concentration in liver of the essential element zinc was found not to be significantly reduced after 4 days of gavage exposure to 2,800 mg/kg/day of di-w-octylphthalatc (Foster et al. 1980), or 7 days of dietary exposure to 1,000 mg/kg/day of di-w-octylphthalate (Oishi and Hiraga 1980). 

One study suggested a possible link of aluminum in public water supplies with the occurrence of Alzheimer disease in 88 county districts of England and Wales. In districts in which the mean aluminum concentration in water exceeded O.llmg/1, rates were 1.5 times higher than in districts in which the mean levels were less than 0.01 mg/1. The results have been challenged on the basis of study design and on the interpretation of the relative significance of the dose of aluminum from water as a fraction of total dietary intake."... 

The developmental studies are intended to provide information on any adverse effects of the food additive on pregnant women and their developing concepms. The study designs used are identical to those used to assess the prenatal toxicity of chemicals, except that dietary administration is preferred over gavage dosing. 

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. 

In a well-controlled study designed to assess the influence of the type and amount of dietary lipid on plasma lipid concentrations in endurance athletes, Lukaskl et al. (46) reported that the plasma response to dietary lipid was not attenuated in men who were physically very active. In contrast, Qulg and associates (47) reported that plasma total cholesterol concentration was lower in subjects who exercised and who ate a diet containing 0.4 or 1.4 gm of cholesterol dally. Thus, the influence of diet on the relationship between exercise and plasma lipids remains equivocal. 

This section describes the rationale for the utilization of dietary tryptophan depletion. Also, it reviews a number of studies designed to determine the consequences of acute tryptophan depletion upon a variety of disorders in humans and conditions in animals. The literature contains a plethora of reports utilizing acute tryptophan depletion. Selected examples have been chosen to illustrate the effects or influences of L-tryptophan levels on a variety of behavioral and psychiatric states. 

These observations lead to the hypothesis that isoflavones may be biologically active, conferring health benefits that could explain the relatively low incidence of hormone-dependent diseases in countries where soy is a dietary staple. However, the effects of soy consumption on hormonal metabolism have been inconsistent, probably as a result of methodological differences in the studies as regards the characteristics of the subjects, study design, isoflavone form and other factors [7],... 

Brito et al. (2003) studied moderate- to low-intensity coinfections caused by intestinal helminthes and Schistosoma mansoni (hookworm, T. trichiura, A. lumbricoides) dietary Fe intake and anemia in Brazilian children, to determine their role in the prevalence of anemia and their relationship to Fe consumption. In rural Brazil, a cross-sectional study design with 1709 children was completed. All participants were... 

Beaton, G. H., Milner, J., Corey, P., McGuire, V., Cousins, M., Stewart, E., de Ramos, M., Hewitt, D., Grambsch, V., Kassim, N., and Little, J. A., 1979, Sources of variance in 24-hour dietary recall data Implications for nutrition study design and interpretation. Am. J. Clin. Nutr. 32 2546. 

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