HOWEVER, it isn't the good doctor's motive but his method that the Mumbai-based gynaecologist team of Dr Aniruddha and Anjali Malpani have put to question. Dr Malpani attacks Dr Joshi's premise that X and Y sperms carry opposite charges. According to him, both carry negative charges, with the degree higher in the Y sperm. He also scoffs at the idea of the zona pellucida having a charge. "The paper on electrical charges unearthed by Dr Joshi was published in 1980. It's outdated now." He says it isn't possible to alter sodium, potassium, magnesium or calcium levels in the blood, let alone in the cells, by dietary changes. "The body protects itself against unequal levels of sodium or potassium or calcium by maintaining a constant. If there's extra calcium in the body, it just throws it out. Also if dietary change in the woman determines the charge on the zona pellucida, then it should attract only either the X or Y sperm. So how do you explain dizygotic twins, or twins of different sexes?"