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Zinc Status Specifically Changes Preferences for Carbohydrate and Protein in Rats Selecting from Separate Carbohydrate-, Protein-, and Fat-Containing Diets^1,2,3,

Division of Nutritional Sciences and Department of Food Science, University of Illinois, Urbana, IL 61801

This study examined how macronutrient intake preferences were specifically altered in the loss of appetite caused by experimentally produced zinc deficiency. Outbred female rats were allowed to freely select from simultaneously provided carbohydrate-, protein-, and fat-rich diets to provide themselves with an acceptable total diet. Rats were divided into two groups and provided the three diets containing either adequate (30 mg/kg; Zn+) or deficient (1 mg/kg; Zn-) levels of zinc (Zn). After 28 d, rats offered the Zn- diet were returned to a Zn+ diet (Zn repletion). Intakes from each of the three macronutrient diets were measured to determine macronutrient preferences of Zn-adequate, Zn-deficient, and Zn-repleted rats. In two 28-d studies involving a total of 66 rats, total metabolizable energy intake in Zn deficient rats was between 20 and 35% lower than in Zn+ rats, and carbohydrate intake accounted for essentially 100% of the lower energy intake. Fat and protein intakes were not affected by Zn deficiency. When Zn-deficient rats were repleted with Zn by providing diets containing adequate Zn, carbohydrate intake was restored to normal levels after 1 d of feeding. A transient difference in protein intake was noted during the repletion period, peaking during d 2–4 of repletion. Protein intake increased by more than 50% during this period. We hypothesize that specific changes in macronutrient intake patterns during development and recovery from Zn deficiency may be reflections, at least in part, of Zn-mediated changes in the central control of appetite.

KEY WORDS: • rats • zinc deficiency and repletion • macronutrient selection • ingestive behavior

¹ Supported by the Illinois Agricultural Experiment Station and International Life Sciences Institute, North America.

² Presented in part as an abstract at the 1994 Experimental Biology meeting, Anaheim, CA [Rains, T. M. & Shay, N. F. (1984) Macronutrient preference in the rat during zinc-deficiency-induced anorexia. FASEB J. 8: A730 (abs.)].

³ The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked "advertisement" in accordance with 18 USC section 1734 solely to indicate this fact.

⁴ To whom correspondence should be addressed.

Manuscript received 22 February 1995. Revision accepted 13 June 1995.