Women amongst some tribals in Nigeria have been known to deliver twins in large numbers and precise reasons for this phenomenon are still obscure. Several questions remain unanswered as to whether the environment has any thing to do with it or whether local water sources are responsible or what role food plays in perpetuating this freak developments. One of the most guessed reasons is that these black women have high levels of follicle-stimulating hormones which could lead to multiple births. Why this happens is still a mystery. Same phenomenon has been reported in some parts of Spain with white women. In all these cases the twins are of dizygotic types or fraternal twins where 2 eggs get fertilized by two sperms each developing in separate sacs in the ovary. As against this monozygotic types result from one egg fertilized by one sperm and splitting into two eggs early in the gestation period within 12 days of conception, both the eggs developing in a single sac. Chances of identical twins are one in 285 and that for fraternal twins is one in 80.
Generally it is believed, though not scientifically proved, that consumption of ovulation-inducing drugs cause multiple births though these are confined to a minority of cases. Many theories, most of them not proven conclusively, float around amongst the fertility experts for explaining this freak phenomenon. Seasonality, maternal age, social class all are supposed to influence the chances for twins. For example In January least number of twins are born while it is highest in July in a country like USA. In some studies consumption of high levels of Vitamin A has been linked to multiple births. Excess consumption of vitamins and minerals by women of child bearing age is also cited as one of the causes. In the Togiak region of Alaska Cow moose are known to be giving birth of twin calves, almost 7 out of ten when they had access to plenty of foods and the rate of twin births declined when food became limited. Folic acid is another Vitamin which, whenever found in high levels in the blood, was implicated in twin births. Diets rich in estrogen like phytochemicals are also suggested as a possible contributing factor by nutritionists as this hormone has a vital role in conception.
If phytoestrogen contents do play a role what could be the make up of a diet ideal for giving birth to twins? There are many estrogen rich foods like yams, barley, some varieties of beans, flax seeds, oats, sesame seeds, soybean, rye, clover, millets, some herbs which are consumed but their relative levels in the regular diet may be the critical factor that may influence conception. It is time that this aspect is given more attention by multidisciplinary scientists so that the role of food is precisely brought out with least ambiguity.
High multiple births reported in Kodinhi, a village in Kerala caught the attention of many media persons and the reason for the presence of 150 twins in a population of 14600 is suspected to be the environment, though no absolute conclusion was possible with practically no scientific investigation. What lends credence to this assumption is that people migrating from other places to this village also showed tendency to conceive twins. Another reports some time back identified a village near Allahabad called Mohammad Umni where there were 33 pairs of twins amongst a population of just 600! According to some scientists who conducted limited studies here that a combination of food, living conditions and high consanguineous marriage could have resulted in such high twin births in this village.
Food scientists, nutritionists and fertility experts must put their heads together to bring out the role of food if any in this phenomenon. If definitive factors are known probably women can decide to go for two children in one go by choosing the right mix of foods instead of undergoing the trauma of child birth twice for the famous "we two and ours two" goal.