Male and femaleWe all know there is a difference between men and women. Aside from the obvious, would it surprise you to learn that the microbes in females behave differently from those in males or may actually be different? We have been focusing so much on the ideal diet, in general and for our microbes, from a nutrition perspective. Yet, researchers are discovering that it is not so simple.

Current research is focusing on learning the connection between gut bacteria and various health conditions. The goal is to learn how to use the new understanding about different strains to develop strategies to help people recover from health conditions. Inflammatory conditions including IBS, colitis as well as diabetes, heart disease and depression are just a few conditions that can benefits from healthy gut flora.

One key area of focus is looking at diet to help manipulate the gut microbes to help these conditions. And here is where a monkey wrench has been thrown into the process. Apparently the gut microbes of males and females react differently to the same food.

In a recent study published in Nature Communications, researchers found several key pieces of information:

  • For too long, the influence of the diet has been assumed to be the same for men and women
  • Sex hormones may be influencing gut microbes and directing the preference for one strain over another
  • This new information means it is no longer as simple as telling people to eat more vegetables
  • Research is going to have to focus on genetics, environment, diet and now hormones and how they all interact. Normally research looks at each of these one at a time. This is no longer enough.
  • And finally, in looking at mice studies, it was found that diet does not vary gut microbes between sexes the way it does in other species such as humans. Since most research is done initially on mice, we must not take any results regarding diet as gospel and wait for the human studies.

That being said gut bacteria from males can make a difference when transplanted into females, according to mice. In a study, female mice, with a 90 percent risk of developing Type I Diabetes (the autoimmune condition), were given gut bacteria from healthy adult male mice.

The females saw increased testosterone, yet their levels did not reach that of males. However, the increase in testosterone did deliver enough active testosterone signaling ability to prevent Type I Diabetes

I am sure this makes the issues of what to eat more confusing. It certainly should make you think twice the next time you pick up a book that is trying to tell what is right or wrong about food. And it definitely means we should reconsider a lot of the information we have received in the past.

In the end we need to use some common sense – we know we need nutrients for our body and for our microbe friends. However, I think we need to develop more an intuition for listening to our body and apparently, to our microbes, which are working hard to communicate with us, about what we should eat.


  1. Individual Diet Has Sex-Dependent Effects On Vertebrate Gut Microbiota, Daniel I. Bolnick, Lisa K. Snowberg, Philipp E. Hirsch, Christian L. Lauber, Elin Org, Brian Parks, Aldons J. Lusis, Rob Knight, J. Gregory Caporaso, Richard Svanbäck, Nature Communications, 2014; 5
  2. Sex Differences in the Gut Microbiome Drive Hormone-Dependent Regulation of Autoimmunity, Janet G. M. Markle1, Science 17, Jan 2013