My name is Akika Altman-Chandler, and I just graduated from the University of Oxford with a degree in Human Sciences. For my undergraduate dissertation, I worked with Teresa Street at the Modernising Medical Microbiology (MMM) laboratory to investigate the influence of the gut microbiome on life expectancy.
To investigate this, I traveled to Nagano, Japan. Nagano is a prefecture in Central/Northern Japan that consistently has the highest life expectancy in the country (87 for females, 83 for males). While there, I worked with the local government and a farming network to recruit residents from a background balanced by age and sex for a small study. In the study, participants completed a survey and provided a stool sample. The survey asked about participants’ age, sex, ethnicity, residential history, medical history, and dietary history. The stool samples were shipped to the MMM laboratory, where I extracted, quantified, qualified, sequenced, and statistically analysed the DNA from the bacteria within them.
One of the most interesting findings from the study was that the stool samples all seemed to have remarkably high Shannon diversity scores. Shannon diversity scores are a statistic that represent how many different species there are in a sample (species richness) and how evenly the different species are distributed (species evenness). In the context of the gut microbiome, high Shannon diversity scores indicate a diverse, balanced community of bacteria. In most populations, gut microbiome diversity scores fall in the range of 1.5-4.5. In this population, gut microbiome diversity scores fell in the range of 3.45-7.45— a range that ranks amongst the most diverse gut microbiomes on record.
After statistically analysing the information provided by participants in the survey, I found that the strongest predictor of Shannon diversity scores was dietary history. Participants who listed that they consumed foods that have been fermented, pickled, or washed in hot spring water at least once a week had diversity scores about 1.5 times higher than those who did not.
This co-variation aligns with Nagano’s cultural practices. Nagano has long produced and consumed foods such as miso, natto, and tsukemono (including nozawana-zuke)). These foods are pre- or probiotic, meaning that they introduce different bacteria into the gut. A diverse gut microbiome can break down a broader range of foods, meaning that there are more molecules available for important physiological processes in your body— be it building muscle, fighting off infections, or repairing tissues. These factors culminate as a potential explanation for Nagano’s historically high life expectancy.
I am so thankful to have had the MMM’s laboratory support throughout this study. I learned so much about microbiology, molecular biology, and just generally about working in a lab. I would like to say a special thank you to Tree, Katie, Val, Nick, Hermione, Cat, and Ali, who taught me the ins and outs of research, as well as a thank you to Invitek Diagnostics and Oxford Nanopore Technologies, who sponsored the scientific equipment.