The widely held belief that men are more attracted to the smell of women during their most fertile periods may not be true after all, researchers say.
A body of research over the past few decades has made a compelling case that female body odour changes with the menstrual cycle, allowing sensitive males to sense (at least in theory) the times when mating is most likely to lead to conception.
But when German researchers had men smell women’s body odor, they found no convincing evidence that a woman’s body odor was more attractive when she was most fertile, nor did they find any changes in the chemical composition of her body odor associated with peak fertility.
The findings suggest that even if a woman’s fertility does change her body odor, it may not be obvious, at least not when they first meet her. The researchers don’t rule out the possibility that men may notice changes in a woman’s body odor if they spend an extended period of time with her.
“We see this as a starting point for a reevaluation of the field,” said Madita Zetsche, a graduate student at the University of Leipzig and first author of the study. “We’re not dismissing past research, but we need to look at this again with the more powerful techniques we have now.”
Zetsche and his colleagues decided to investigate this question because they could not find any previous studies showing that fertility leads to chemical changes in women’s body odor. “That would be important to see an effect,” Zetsche said.
The researchers recruited 29 non-smoking heterosexual women aged 20 to 30 years. None of them were using hormonal contraception. The researchers then collected underarm odor samples from the women 10 times before, during, and after ovulation. They used ovulation tests and levels of the hormones estradiol and progesterone in their saliva to track the women’s cycles.
write Proceedings of the Royal Society BWhen the researchers compared samples taken from women’s fertile and non-fertile days, they found no significant differences in the chemical composition of body odour.
In the next phase of the study, the researchers asked the women to attach the cotton pads to the skin under their arms and wear them overnight for 12 hours. They then asked 91 men aged 19 to 40 to rate the scents of women they smelled at different stages of their menstrual cycle. No man smelled the same woman twice.
Again, there was no convincing association between ratings of men’s smell and women’s fertility, suggesting that even if fertile women do smell different, the effect may be so subtle that men don’t notice it when they first meet them.
The study comes after several studies have claimed that women’s body odor reflects fertility. More than a decade ago, researchers at the University of California, Los Angeles found that men Men are more likely to be attracted to the body odor of women of childbearing ageScientists have begun to wonder whether a woman’s smell might influence a man’s sexual approach. In 2018, a research team led by Daria Noch, a professor of social neuroscience at the University of Bern, published a paper titled “How Women Smell Their Men.” Reproductive hormone levels explain individual differences in women’s body odor.
Nock called the latest study “interesting” but “surprising” from an evolutionary perspective. “I wonder what the results would have been like if the authors had taken into account the major histocompatibility complex (MHC), a very important factor that influences body odor preferences,” he said. “MHC genes affect the production of molecules in sweat and body fluids that contribute to a person’s unique smell. Some studies suggest that men prefer the body odor of women with a different MHC.”
