According to Dr. David Williams research on sweet potatoes in 1989 in my “News From Around the World” If you want twins, then adding generous amounts of sweet potatoes to the diet may be the answer.
Professor Percy Nylander of the University of Ibadan, located in Nigeria, has done extensive studies of the native Yoruba tribe who have the highest rate of double births in the world. It was discovered that their diet is extremely high in yams (or sweet potatoes). Yams have been used for centuries to relieve hormone problems like miscarriages, infertility, abnormal menstruation and even asthma. In the 1930’s the hormone cortisone was first isolated and extracted from the adrenal glands of cattle..
Also Research into multiple births carried out at Lagos’s University Teaching Hospital has suggested that a high level of a chemical found in the Yoruba women and the peelings of the tuber could account for the high level of multiple births.
A consultant gynaecologist at the hospital explains:
‘These substances are usually linked to the release of more than one egg, which usually leads to twin pregnancies. That means that there is possibly an environmental factor that encourages the high level of this chemical substance.’
The doctor, who has witnessed many multiple births at the run-down hospital, continues by linking the staple diet of the women to the prevalence of the chemical:
‘Numerous works has shown that the tuber food of the Yoruba women, especially the peelings, contains a very large amount of these chemical substances. These women have a disproportionately large amount of these chemicals in their system and this encourages the release of more than one egg. There is enough reason to believe in this theory.’
So, could it be that eating tuber peelings leads to multiple births? The International Institute of Tropical Agricultural is uncertain.
Following research into the reputed high oestrogen content of a yam like vegetable called agida, Robert Asiedu is sceptical of the tuber link. Citing the specific cultivation of yams in regions of Asia for their contraceptive qualities, in an article for Science In Africa magazine, he commented
Later, it was learned that the hormone could be extracted more economically from the Mexican yam. Not only do these yams contain natural cortisone-like substances, they also have other steroid-like compounds easily converted to sex hormones. In fact, they have often served as the source for the raw materials in making oral contraceptives.
These compounds found in yams, trigger the release of FSH (follicle-stimulating hormone) which stimulates the ovaries to release more than one ovum (or female egg cell). If two or more then become fertilized, it results in multiple pregnancies. As in other mothers who give birth to twins, women in the Yoruba tribe have extremely high levels of FSH. I can’t tell you exactly how much sweet potato you’d need to eat a day to increase the chance of having twins, but some researchers feel one-half cup daily might do the trick.