Last month I wrote a post stating my concern for the growing number of “pregnancy” websites and blogs that promote ways in which women can conceive twins. Some of the advice is dangerous such as advocating progesterone creams and the prescription drug Clomid but other suggestions are just silly such as eating yams. Lots of yams.
According to the number of hits that post received, I think I hit a nerve. Lots of readers found the post not by accident but by searching for, “twins and yams,” or “what do I eat to conceive twins?” Obviously many women out there are strongly considering this as a viable solution to conceiving twins. And it made me wonder, “Well, just how many yams do you have to eat to conceive twins?” To get to the answer, we need to go back to where this fact/rumor/idea all began.
The rate of fraternal twins (or dizygotic) varies greatly from country to country, culture to culture, ethnic group to ethnic group. Although their rate of twinning has rapidly increased in the past few years along with many other developing countries, the Japanese have the lowest incidence of twinning. (Back in the late 1990s, it was estimated that the Japanese had six twin pairs per every 1,000 births.) On the other hand, the Yoruba tribe in Nigeria, West Africa has the highest rate with 45 pairs per 1,000 births. That means that nearly one in 11 Yoruba is a twin! (These days in the United States, one in 33 births results in a twin.)
Researchers have long speculated that it’s the Yoruba diet that can help explain this Herculean statistic. Specifically, it’s the Yoruba’s daily diet of cassava (a type of yam). Although the Yoruba diet also includes plantains, taro, maize and beans, it’s the cassava that contains phytoestrogen, an estrogen compound that increases a woman’s follicle-stimulating hormone (FSH), and may induce a higher rate of ovulation.
Did you catch that? It’s a “daily diet.” Yoruba females consume a lot of cassava from the cradle to the grave. They eat the yam roasted, broiled, dried, or pounded into a paste to make iyan, a popular staple dish. The dried yam is often ground up and added to boiling water to create a porridge-like dish called amala and then eaten with a stew. They even mill the yam to create flour. But when Yoruba women move away from their villages and into cities where most likely their diets change (probably by including more variety of vegetables and meat, and less yams), their twinning rate decreases! This would further suggest that the estrogen effect from the yam is immediate rather than cumulative. Still, it would seem that you’d need to eat more than just one serving of the cassava to produce twins. But how much is still unknown.
And then there’s that one last burning question: Has anyone ever even seen a cassava in her local supermarket?