Even though soy foods possess several positive effects on human health, it will toxic in different ways on our health when we consume soy foods than its recommended dose. This is because soy foods contain major quantities of  bioactive compounds with toxic and adverse effects. For an example, disruption of the intestinal brush border membranes, atrophy of the microvilli and reduced viability of the epithelial cells was observed with the use of raw soybean due to existence of toxic compounds such as trypsin inhibitors and lectin. As a result it will bind to the intestinal epithelium and cause the gastrointestinal disturbance by altering the body mechanism. 

Effect on endocrine gland
Number of phytoestrogens present in soy food are potential endocrine disrupting chemicals that interrupt the normal functions of hormones as well as reproductive system such as zenistein, biochalin A and daidzein. Moreover, they significantly effect sexual development in terms of puberty time alteration, estrogen cycle impairment, functions of ovary and alterations of pituitary as well as hypothalamus dysfunctions. 

Effect on mammary gland 
The regular consumption of soy foods cause breast abnormalities due to the powerful estrogenic effects and also genistein, which is a chief isoflavone present in soy food. This affects the development of the mammary gland and as a result will stimulate breast cancer development via its estrogenic activities. 

Effect on male reproductive system
Genistein in soy bean adversely causes the progression of the male reproductive system by its estrogenic action. Moreover, studies have indicated that the reduced sperm count andincreased sperm motility in the stage of juvenile period. 

Effect on thyroid gland 
Soy products contain potent thyroid inhibitors such as daidzein. Also soy foods act as an anti-thyroid agent which decreases the absorption of iodine. According to the studies hypothyroidism and goiter were reported in infants receiving soy-containing formula.  

Based on the thyroid function test, many researchers have highlighted that the high consumption of soy foods cause thyroid suppression and goiter in iodine-deficient rodents and infants. 

The further study evidenced that consumption of soy may gradually reduce the functions of thyroid hormones and utilization of iodine. However, it can be reversed by the dietary supplementation of adequate iodine.

Not only soy bean, any food will be beneficial if we take it in an adequate quantity; in other words the recommended level. However, overconsuming without considering the recommended quantity, will be toxic to us in different ways.  

Therefore we have to pay more attention to what we select as our diet.

(The writer is a medical laboratory technologist at a private hospital and holds a MSc. Degree in Industrial and Environmental Chemistry from the University of Kelaniya and a BSc. Degree in Food Production and Technology Management from the Wayamba University of Sri Lanka)