It used to be thought that our genes were our fate, but a lot has changed in recent years, particularly in the field of nutrigenomics and epigenetics. In fact, new research suggests that your health and happiness could depend more on your microbiome than your DNA, and that instead of being inherited, your microbiome is more influenced by your environment than by your genes.
Your genes and your gut
For years, the general view has been that your genes are the main factor in predicting your risk of certain health issues, and that, in large part, you inherit your microbiome, meaning that the influence of environment is minimal. Now, however, researchers have found evidence of the opposite: less than a tenth of your microbiome is inherited, and your microbiome is a better predictor of your risk of high cholesterol, obesity, and other health traits.
One of these recent studies was carried out in Israel and looked at the gut bacteria of over 1000 Israeli adults. They included people of Ashkenazi, North African, Yemenite, Sephardi, and Middle Eastern descent, as well as some volunteers with other origins and looked at something called beta-diversity in microbiome samples. Beta-diversity is a measure of the difference between samples taken from different people (alpha-diversity is the diversity within a sample from one person or site).
The researchers found that the participants' microbiomes did not rely significantly on their ancestry. Instead, environment, not genetics, played the largest role in determining the microbiome. Using data from another study, the researchers determined that 1.9-8.1% of the microbiome is inheritable.
This adds weight to an earlier study which found that people who live together are more likely to have similar microbiomes than related individuals who have never lived together. This study determined that 5.3-8.8% of the microbiome is inherited, with certain bacteria more likely than others to be passed on to the next generation. For instance, Ruminococcaceae and Lachnospiraceae families appear to be mostly determined by inheritance, while the Bacteroidetes species are mostly environmentally determined.
Microbiome as Medicine
Why does this matter? Well, because it's increasingly acknowledged that the makeup of bacteria in your gut has a profound effect on your health. In fact, this effect is much greater than once thought, influencing everything from your risk of high cholesterol and obesity, to your cognitive and emotional wellbeing. And, if your environment, not your genetics, determines the majority of your microbiome, this gives us a way to significantly influence a whole host of health outcomes.
For example, by combining genetic data and microbiome data, the researchers in the Israeli study were better able to predict several health factors. They even found that the microbiome contributed 36% of the variation in levels of high-density lipoprotein (HDL) cholesterol, and 25% of variation in body mass index (BMI).
Given that the number of bacterial cells in your body vastly outnumber your own cells, perhaps this 'news' isn't all that surprising. People have long been using fermented foods and, more recently, probiotic supplements, to influence health outcomes. In the coming years, it seems that researchers may be more focused on the microbiome as a therapeutic target. Indeed, some researchers are already looking at the use of probiotics and fecal transplants to correct dysbiosis for better prognosis in chronic liver disease, as well as stroke, diabetes, and other metabolic diseases.
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Goodrich, J.K., Davenport, E.R., Beaumont, M., et al. (2016). Genetic Determinants of the Gut Microbiome in UK Twins. Cell Host Microbe, May 11; 19(5):731-43. https://www.ncbi.nlm.nih.gov/pubmed/27173935/
Li, X., Watanabe, K., & Kimura, I. (2017). Gut Microbiota Dysbiosis Drives and Implies Novel Therapeutic Strategies for Diabetes Mellitus and Related Metabolic Diseases. Frontiers in Immunology, 8, 1882. http://doi.org/10.3389/fimmu.2017.01882
Rothschild, D., Weissbrod, O., Barkan, E., et al. (2018). Environment dominates over host genetics in shaping human gut microbiota. Nature, Mar 8;555(7695):210-215. doi: 10.1038/nature25973.
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