Soy milk toxicity: Cause for concern

S Senthilkumaran¹, N Elangovan², RG Menezes³, P Thirumalaikolundusubramanian⁴,  
¹ Department of Emergency and Critical Care Medicine, Sri Gokulam Hospitals and Research Institute, Salem, India
² Department of Biotechnology, Periyar University, Salem, India
³ Department of Forensic Medicine and Toxicology, ESIC Medical College and PGIMSR, Bangalore, India
⁴ Department of Internal Medicine, Chennai Medical College Hospital and Research Center, Irungalur, Trichy, India

Correspondence Address:
S Senthilkumaran
Department of Emergency and Critical Care Medicine, Sri Gokulam Hospitals and Research Institute, Salem
India

Full Text

Sir,

The thought-provoking report by Wiwanitkit [1] is timely, as soy milk has been prescribed by physicians, pediatricians, and practitioners of alternative and modern medicine. Also, it is promoted vigorously in the media in an unregulated manner. The author had arrived at a diagnosis based on proper diet history and applied his knowledge of toxic effects of soy, which have helped to demystify the clinical and laboratory challenges observed in this case. [1] We would like to mention four things related to soy toxicity: First on the additional mechanisms for toxicity, second on allergy to soy, third on prevention, and fourth on an area for research.

The author has highlighted the hepatotoxicity of soybean to isoflavone and soy peptides. At this juncture, we would like to mention that soybean is rich in phytoestrogens, which have estrogenic and anti-estrogenic properties, and these compounds are currently used extensively as an alternative to traditional hormone-replacement therapy. Though it is still available from soy seed, a food material, now it is marketed as health food supplements or drinks. Tablet form of soy extract may soon be made available over the counter as a "natural" hormone-replacement therapy pill. Interestingly, these compounds alter the catabolism of estrogen to 4-hydroxyestrone (4OHE1), a putatively potent genotoxic estrogen, which on accumulation contributes to hepatotoxicity. [2] Single-nucleotide polymorphism of lignans involved in the estrogen pathway might also have contributed for the same. [3] Hepatotoxicity due to soy has already been demonstrated in cheetahs. [4]

Soybean and its derivatives have become ubiquitous in vegetarian and many meat-based food products. As it ranks among the "big 8" of the most allergenic foods, the incidence of soy-caused allergies is expected to escalate with increased consumption. [5]

The old adage, "anything in excess is harmful to health," holds good to soy milk too. So, to prevent its toxic effects, the hazards of excess soy milk consumption should at least be printed on the label and in the leaflet accompanying soy preparations. Also, practitioners of all systems of medicine should be informed on the mechanisms and pattern of toxicity due to excess use of soy and individual variations for susceptibility. Equally, the myth of harmless nature of "natural products/medicine" has to be eliminated through health education and regulated marketing techniques.

The potential area for research is to find out the susceptible individuals, as biological effects are influenced by many factors such as dose, duration of use, protein binding affinity, metabolism, intrinsic estrogenic status, and intestinal microflora. Further clinical studies are necessary to determine the potential health effects of these compounds in specific population/groups. Let our goals be "learn, understand, and act more to prevent." Further, one has to exercise caution before using any hormone-containing material, be it natural or synthetic.

References