A major component of many low-carbohydrate diets, such as the Atkins diet, is 95% lean ground beef, typified by a "hamburger without the bun" (56). Lean ground beef consists of 35% fat and 65% protein (%Kcal), in addition to 65 mg cholesterol and 55 mg sodium per 85 gram portion. The fat portion consists of approximately equal amounts of saturated and mono-unsaturated fats (FDA food label). Surprisingly, we could only find one previous study in which Drosophila were fed dietary beef (63), and one microarray study where mice were fed beef tallow (64). The Drosophila beef paper was published in 1979
and the title is "Failure of irradiated beef and ham to induce genetic aberrations in Drosophila" (63). The purpose of this paper was to allay the unjustifiable fear, which, unfortunately, is still common among the public, that irradiated food is carcinogenic in humans. In addition to the mouse microarray paper cited previously (64), several other laboratories also fed mice pure beef fat (tallow) to induce obesity (65,66). However, few humans consume large amounts of pure beef tallow, so the application of these results to humans is questionable.
In the experiments described in this chapter, we fed flies a diet containing 95% lean ground beef in order to determine the metabolic effects of consuming beef. Surprisingly, to our knowledge, 95% lean beef diets have not yet been used for nutrigenomics studies in animal models. As described below, our findings suggest that diets rich in 95% lean ground beef, soy, or palmitic acid prolong the larval period, but decrease the mean and maximal life span. However, only beef was able to significantly decrease triglyceride levels in adult flies. In the final section, we will discuss the implications of these findings, if any, in terms of human health and life span.
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