A study conducted at King’s College London under the leadership of Professor Lynn Fraser, has found that a number of substances may have a seriously negative effect on the human fertilization process.
The presentation to a meeting of the European Society of Human Reproduction and Embryology in Copenhagen showed that a chemical known as genistein causes human sperm to “burn out” before having a chance to penetrate the wall of the egg and initiate fertilization.
Genistein is found in soya, tofu, and legumes. Professor Fraser, an expert in reproductive biology, suggests women who are ovulating should avoid or seriously limit their intake of these foods in order not to expose sperm to the compound.
In related research, two other estrogen-like chemicals were identified as having a similar debilitating effect on sperm. They are 8-prenylnaringenin, found in hops and beer, and nonylphenol, which is contained in industrial products such as paints, pesticides, and cleaning agents.
Genistein and the chemicals with similar effects cause the cap on the head of a sperm (acrosome) to rupture prematurely. This releases the enzymes needed to drill through the egg wall much too soon thereby preventing fertilization. Thus, while the sperm is still alive and moving actively, it has lost its ability to fertilize the egg.
Although Professor Fraser and other experts describe the results of the study as surprising and troubling, they also point out that Asian societies with traditionally soy-rich diets show no signs of reduced fertility and effects on sperm in the lab are often quite different than what may happen in real life.