Journal of Food, Agriculture & Environment, Vol.4 (3&4), July-October 2006 45 Dietary phytates protect the rat against lead toxicity Florencia Cúneo 1 , Jaime Amaya-Farfan 1* and Marcelo A. Morgano 2 1 Dept. of Food and Nutrition, School of Food Engineering, State University of Campinas, R. Monteiro Lobato, 80 - DEPAN& NEPA-UNICAMP, Campus Zeferino Vaz, 13083-862 Campinas, SP, Brazil. 2 Food Chemistry and Applied Nutrition Center, Institute of Food Technology, ITAL,Campinas, SP, Brazil. *e-mail: Jaf@fea.unicamp.br, fcuneo@yahoo.com Received 7 June 2006, accepted 28 September 2006. Abstract Lead uptake by growing 60 days old Wistar rats from diets contaminated with 160 μg g -1 PbO added with rice bran (RB) was investigated. Eight diets based on the AIN-93 were formulated to furnish either 0, 3 or 12 mg g -1 total phytates, while controlling the amounts of insoluble fiber at either 10 or 50 g kg -1 . Two additional intermediate levels of phytates in the diet were obtained by adding partly hydrolyzed bran using exogenous phytase. After four weeks of feeding, the lead contents of blood, liver, kidney and bone were determined by atomic emission spectrometry. The accumulated metal in bone, kidney and liver were inversely proportional to the quantity of phytates ingested. It was possible to isolate the effect of the phytate on the lead accumulation in femur, liver and kidney of the animals consuming RB from that of the insoluble fiber. Significant reductions (P<0.05) were observed in bone from 65 to 35 to 15 μg kg -1 , in kidney from 13 to 8 to 3.4 μg kg -1 and in liver from 1.34 to 0.9 to 0.5 μg kg -1 , as the phytate content rose from 0 to 3 to 12 mg g -1 of diet, respectively. Differences in blood lead were significant only between the control diet and that with the higher addition of bran. The RB even at its lowest level (3 g kg -1 phytate) showed to be an effective dietary protectant against lead absorption and uptake by the animal, suggesting that too low phytate ingestion, as is often the case with some modern diets, increases the risk of lead poisoning, even from background contamination. Key words: Phytic acid, whole grains, lead toxicity, heavy metals, modern diet, chelates. Introduction There is a growing concern about the impact of the modern diet on the general state of health of the population. Over the past half century the underlying emphasis of food technology, allied to the desire to improve the nutritional status worldwide, has lead to the maximization of nutrient bioavailability and the nutritive value of virtually all foods. One result, for instance, can be seen today in the ability of refined grain flours and their products to reach the most remote places of developing countries. For decades, phytates in foods have been termed as undesirable or antinutritional due to the fact that this family of substances makes such dietary limiting cations as zinc, iron and copper unavailable to humans 1 . Although the primitive diet must have supplied too generous an amount of phytates to early man, a number of beneficial properties have been pointed out for these substances during the last decade 2 . The protective action of phytic acid has been associated to its cation chelating ability, thereby decreasing the iron-mediated colon cancer risk and lowering serum cholesterol and triacylglycerides in experimental animals. Phytic acid has also been considered as a natural antioxidant and is thought to reduce lipid peroxidation and serve as a food preservative 2 . However, no authoritative statements have been issued on a desirable level of ingestion of dietary phytates or low observed adverse effects level (LOAEL). It is quite possible, for instance, to find individuals of urban communities, particularly young persons, consuming diets almost totally devoid of phytates. One concrete concern with regard to public health, however, is the modification of the absorption profile of inorganic ions by ingestion of phytates, including heavy metal contaminants 3, 4 . It is interesting to note that the physicochemical characteristics responsible for the well known antinutritional effects 5, 6 can also be involved in chelating heavy metals present in the food or in the intestine. Both calcium phytate 7, 8 and dietary insoluble fiber 9 , when individually incorporated to the diet of experimental animals have shown beneficial effects measured by reduced levels of lead deposition in diverse organs. Toxic metals, such as lead, be it of environmental, occupational or dietary origin, continue to pose a threat to Brazilian public health 12, 13 . The objective of the present work was to assess in rats the effect of consuming a diet modified with rice bran, as a source of phytate and fiber, in the presence of contaminating levels of lead. For that purpose, a standard rat diet was contaminated with lead oxide (PbO), but causing no visible signs of poisoning in the animal, and the impact on the levels of lead in blood, liver, kidney and bone prompted by the contamination evaluated in comparison with that of a diet modified by substituting the standard cellulose for rice bran. Materials and Methods Raw materials and diets: The defatted, stabilized rice bran (RB) was a gift of IRGOVEL, Pelotas, RS, Brazil. Rice bran is the by- product resulting from the polishing of brown rice, accounting for approximately 50 g kg -1 of its raw weight and a large portion of the www.world-food.net Journal of Food, Agriculture & Environment Vol.4 (3&4) : 45-49. 2006 WFL Publisher Science and Technology Meri-Rastilantie 3 C, FI-00980 Helsinki, Finland e-mail: info@world-food.net