This study was carried out to investigate the effect of prolonged and excessive consumption of soybean and monosodium glutamate on blood glucose, insulin, and liver function. The quantitative and qualitative determination of oestrogen-like compounds was carried out by chromatography. A total of two hundred and ten (210) Wistar rats (70 – 78g) were divided equally into three groups representing the various experimental durations (2, 4, and 6 months). Each of these groups was further sub-divided equally into fourteen (14) subgroups (7 groups for male rats and 7 groups for female rats). Out of the 7 groups for both the male and female rats, a group represented the control rats only fed commercial rat chow and water, whereas the rest were orally administered any of the 1000 mg/kg b.w (low dose), 2000 mg/kg b.w (medium dose), or 3000 mg/kg b.w (high dose) of aqueous extract of monosodium glutamate or soybean. Diadezein (42.63 mg/100g), and genistein (28.49 mg/100g) were the two most abundant oestrogen-like compounds. After 6 months administration the high dose (H.D) MSG and soybean, significantly altered the blood glucose and insulin levels of both the male and female rats. The liver enzymes levels of the female rats were significantly elevated after 2 months of administration of H.D MSG and soybeans. All the doses of soybean administered for 6 months significantly elevated the liver enzyme levels compared to the control. The administration of H.D MSG for 4 and 6 months significantly increased the total bilirubin levels of female rats while no significant changes were observed following soybeans administration. For the male rats, no significant changes were observed on the total bilirubin levels after the administration soybeans, whereas H.D MSG for 2 months significantly increased the total bilirubin levels (12.00 µmol/l) compared to the control (8.60 µmol/l). This study has shown that regardless of the presence of medicinal compounds in soybeans, excessive prolonged intake compromises the functional integrity of the liver while MSG even at minimal doses poses serious health risks.