The menstrual blood of a woman put into a mans food can cause him to fall in love with the woman who the blood belongs to.
As the first born female child of Nigerian parents, I was often responsible for several household chores. One of these chores was cooking dinner for the family when both of my parents were at work. On one particular occasion, I told my mother that I was going to hire a chef when I was an adult so that I would not have to cook. My mother looked at me very seriously and told me that it was necessary for me to learn to cook. She told me that I should never hire a cook or maid because she might try to steal my husband. She gave several means by which this might occur, but the story that stuck with me was of a woman who she knew who claimed that the reason her husband had divorced her was because the maid was putting blood in his food. He was indeed married to his former maid, but I cant really decide what to attribute that to.
In the realm of folk belief, blood is often linked to passion, strength, death, life, and courage. Many cultures believe that blood (particularly menstrual blood) has curative properties, and many more believe that a womans menstrual blood holds the power to captivate a lover. It has been said that a man who ingests the menstrual blood of a woman is bound to her forever. It is considered the most potent substance for love potions.
These beliefs are still regarded as true by certain groups around the world. Growing up in a Muslim family in a large city in Nigeria, my mother would probably never have been exposed to these ideas had it not been for the village children who attended boarding school in the city. She learned this superstition from her peers as a youth. Many who use menstrual blood in spells claim that the use of menstrual blood in rituals was very common before the fear of blood borne diseases arose. They contend that one can surmise this from the root of the word ritual, because it is derived from the Sanskrit word meaning menses. Other scholars argue that rtu simply refers to any regular order in nature.
Buckley, Thomas, and Alma Gottlieb. Blood Magic. CA: University of California P, 1988.
Sternbach, Ludwik Journal of the American Oriental Society, Vol. 98, No. 2 (Apr. – Jun., 1978), pp. 195-198 <http://www.jstor.org/sici?sici=00030279(197804%2F06)98%3A2%3C195%3ARISL%3E2.0.CO%3B2-H&cookieSet=1>