Abstract
Chemically, soy contains a group of phytoestrogens called isoflavones, pre-dominantly genistein and daidzein. The aim of the present study was to determine the effects of post weaning consumption of dietary soy isoflavones on prepubertal and postpubertal serum levels of some reproductive hormones of male Wistar rats. The study involved investigating the effects of different doses of isoflavones in the diet. Male rats were weaned on either soy isoflavone free diet or on isoflavone containing diets, formulated by adding increasing amounts of Novasoy, a commercially available isoflavone supplement to the isoflavone free diet to give varying concentrations of isoflavones. Three isoflavone containing diets were used and these had 74.5, 235.6 and 1046.6 mg total isoflavones/kg pelleted diet. These diets represented the isoflavone concentration lower, equal to and more than that found in soy-based infant formulas respectively. The results obtained showed that; administration of low doses soy isoflavones (74.5 mg/kg) produced significant (p < 0.05) increase in serum Antimullerian Hormone levels both in prepubertal and post pubertal rats, when compared to the control groups. Administration of moderate doses of isoflavones (235.6 mg/kg) produced significant (p < 0.05) increase in serum levels of Antimullerian Hormone and Inhibin in both prepubertal and post pubertal rats when compared to the control groups. Administration of high doses of isoflavones (1046.6 mg/kg) produced significant (p < 0.05) increase in serum levels of Inhibin in both prepubertal and post pubertal rats when compared to the control groups. From this study, it was concluded that post-weaning consumption soy isoflavones produced significant changes in serum Inhibin and Antimullerian Hormone both in prepubertal and post pubertal male Wistar rats and the changes were dose dependent.
Highlights
Most babies Worldwide are weaned on soy-based food supplements [1]
The aim of the present study was to determine the effects of post weaning consumption of dietary soy isoflavones on prepubertal and postpubertal serum levels of some reproductive hormones of male Wistar rats
Administration of moderate doses of isoflavones (235.6 mg/kg) produced significant (p < 0.05) increase in serum levels of Antimullerian Hormone and Inhibin in both prepubertal and post pubertal rats when compared to the control groups
Summary
Most babies Worldwide are weaned on soy-based food supplements [1]. Soy Based Infant Formulas (SBIFs) were developed due to the need for a non-milkbased formula alternative for infants with allergy or those intolerant to cow’s milk formulas [2]. Isoflavone usage has increased because of the correlations between the high soy isoflavone levels in Asian diets and the reduced incidence of coronary heart disease as well as prostate, colon and breast cancers which suggest a possible protective effect of isoflavones [7]. Despite the protective effects of phytoestrogens on the body, several animal studies investigating the safety of soy isoflavone consumption have demonstrated some deleterious effects on reproductive success and health [8]. Various studies have been done using different animal models to show the effects of isoflavones on the reproductive parameters, and such effects included; a decrease in plasma levels of testosterone as well as erectile dysfunction in rats [10], glandular metaplasia in prostate and bulbourethral glands as well as gynecomastia in cattle [11], a decrease in litter size and increased post-implantation loss in mice [12]. While most of the researches focused on assessing the effects of isoflavones on postpubertal parameters, the researches which assess the effects of isoflavones on prepubertal parameters have not been fully demonstrated [15]
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