Reheating of soy oil is detrimental to bone metabolism in oestrogen deficient rats

• Published in: Singapore medical journal Vol. 48; no. 3; pp. 200 - 206
• Main Authors: IMA-NIRWANA, S, AHMAD NAZRUN, S, YEE, L. J, LOH, H. C, YEW, S. F, NORAZLINA, M, ABDUL GAPOR, M. T, KAMSIAH, J
• Format: Journal Article
• Language: English
• Published: Singapore Singapore Medical Association 01.03.2007
• Subjects: Animals; Biological and medical sciences; Bone and Bones - metabolism; Chromatography, High Pressure Liquid; Female; General aspects; Hot Temperature - adverse effects; Interleukin-6 - blood; Medical sciences; Osteocalcin - blood; Osteoporosis - metabolism; Ovariectomy; Rats; Rats, Sprague-Dawley; Soybean Oil - chemistry; Soybean Oil - pharmacology; Tocopherols - analysis; Vitamin E - analysis; soy oil; Rat; Deficiency; Rodentia; Estrogen; vitamin E; Soybean; E-Vitamins; Metabolism; Vertebrata; Heat; Mammalia; Oil; bone metabolism; Animal; heated soy oil; Tropical medicine; Bone; Sex steroid hormone; oestrogen deficiency
• ISSN: 0037-5675

The short-term and long- term effects of heated soy oil on bone metabolism in ovariectomised Sprague-Dawley rats were studied. Three-month-old female rats, were divided into five groups: normal control (NC); ovariectomised control (OVXC); ovariectomised and fed rat chow with added fresh soybean oil (SOF) or once-heated soy oil (SO1) or five-times-heated soy oil (SO5). Short-term parameters measured after one month were serum interleukin-6 (IL-6) and osteocalcin. Long-term parameters measured after six months were the structural bone histomorphometrical parameters. Vitamin E content in the soy oil subjected to the different heating treatments were also measured. Rats in the SO5 group had higher levels of IL-6 after one month compared to the other four groups. Osteocalcin levels in the SO1 and SO5 groups remained high after treatment, while those in the NC and SOF groups declined. After six months, bone mass declined in the SO5 group. Vitamin E assay in the oils showed that levels of alpha-tocopherol decreased after heating the oil once and five times, while levels of gamma- and delta-tocopherols only declined after heating five times. Repeated heating of soy oil destroyed the tocopherols causing raised serum IL-6 and osteocalcin levels, leading to increased bone resorption and osteoporosis in the long term.