Young Women Have Higher Gut Bacterial Diversity than Young Men

In a new study in the journal mSystems, an international team of researchers analyzed the relationship of age and sex to gut bacterial diversity in adult cohorts from four geographic regions. They found that younger age is positively associated with gut bacterial diversity in both men and women, but young women display greater biodiversity than young men.

de la Cuesta-Zuluaga et al find age and sex of an individual strongly influences the bacterial diversity of the gut microbiome. Image credit: University of California, San Diego School of Medicine.

Microorganisms in the human gut play a role in health and disease. Since they may be pivotal in the development of microbial therapies, understanding the factors that shape gut biodiversity is of utmost interest.

“It is well known that the microbiome changes from childhood to adulthood. We wanted to look at changes that happen in adulthood, from young adults to middle-aged adults, and if those changes are influenced by sex and age,” said Dr. Varykina Thackray, from the University of California, San Diego School of Medicine.

“Our findings show a woman’s microbiome may be more diverse than a man’s and mature sooner.”

Greater microbial diversity in the female gut may be associated with sex hormones.

“Our results suggest that, because girls go through puberty earlier than boys, the microbiome of men may need time to catch up,” Dr. Thackray said.

The scientists analyzed the gut bacterial diversity of approximately 8,900 adults, ages 20 to 69 from four geographic regions: the U.S., the U.K., Colombia, and China.

In terms of age, they found that in the U.S., U.K. and Colombia cohorts, bacterial biodiversity correlated positively with age in young adults (ages 20 to 45) but plateaued around age 40, with no positive association observed in middle-aged adults (ages 45 to 69).

“We were intrigued to see that the differences we detected between men’s and women’s microbiome in young adulthood were less obvious in middle age,” Dr. Thackray said.

“One way of thinking about this is like the growth of plants in a newly cleared field. Over a period of time, a diverse ecosystem of plants would become established and grow in the field until no more space was available.”

“Our study suggests that the human gut microbiome continues to diversify until age 40 or so when it seems to plateau, as opposed to continuing to become more and more diverse over a lifetime.”

The team found little association of biodiversity with age or sex in the Chinese cohort.

“The idea that sex and age play a role in microbiome diversity may not be universal,” Dr. Thackray said.

“There is a lot more work that needs to be done with future longitudinal studies to understand the effects of factors like puberty, steroid hormone levels and hormonal contraceptives on diversification of the gut microbiome during adolescence and young adulthood.”

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Jacobo de la Cuesta-Zuluaga et al. Age- and Sex-Dependent Patterns of Gut Microbial Diversity in Human Adults. mSystems, published online May 14, 2019; doi: 10.1128/mSystems.00261-19