Nutrition plays a critical role in shaping microbiome health. Learn how researchers at Mount Sinai’s Institute for Exposomic Research unveil the complex relationship between human diet and the gut microbiome.
Nutrition plays a critical role in shaping microbiome health, and altered microbiome populations have recently been found to be associated with adverse health outcomes including obesity, Type 2 diabetes, cardiovascular disease, immunological disorders, irritable bowel syndrome, allergies, autism and cognitive decline.
Ryan Walker, PhD, Assistant Professor of Environmental Medicine and Public Health at the Icahn School of Medicine at Mount Sinai, is carrying out innovative trials to better understand the complex relationship between human diet and the gut microbiome.
“I try to seek out novel questions people haven’t addressed yet, and I try to find new ways that exposures and nutrition affect the gut microbiome,” says Walker, director of the Human Metabolism and Physiology Lab at Mount Sinai Morningside, where he studies the role of genetics, environmental exposure and diet on risk for obesity, type 2 diabetes and related diseases.
“Typically, researchers study how one nutrient affects one classification of bacteria. That’s a very myopic view. I’m really trying to understand a myriad of exposures affecting the microbial community as a whole, to see if there are any measurable differences on health outcomes,” he says.
Studying the gut microbiome can be incredibly complex and difficult, according to Walker. Humans are hosts to approximately 10 trillion more microbes than our own human cells. And while the human genome contains 27,000 genes, the gut microbiome comprises more than 3 million genes.
In a recent pilot study, Walker found that a diet based on typical adolescent daily intake of high fructose corn syrup alters the structure and diversity of the gut microbiome, and may increase risk for Type 2 diabetes. An estimated twenty percent of young adults drink three or more cans of soda a day, equal to more than 25 percent of the recommended daily calorie intake for adults. He and collaborators took stool samples from an adult group that consumed 25 percent of total daily calories from fructose, then transplanted the stool samples into mice without a gut microbiome. Within weeks, the transplanted mice increased their body fat content, had more inflammation and exhibited increased activation of genes in their livers related to nonalcoholic fatty liver disease, as compared with the control mice. The mice developed unhealthy metabolic phenotypes based on the altered microbiome from human donors alone, suggesting that fructose changes to gut microbes may be involved in risk for metabolic disease.
Walker is currently expanding his study of environmental exposures and their effects on the microbiome beyond nutrition, to include environmental chemicals. He is leading a pioneering study that is examining whether PFAS and other common environmental chemicals are found in breast milk of mothers in Spain, to determine if these chemicals affect the breastmilk microbiome and development of the infant gut microbiome.
“Breast milk is full of incredibly beneficial microbes which can influence an infant’s microbiome during a critical window of development. The question is, are microbes and other components of breast milk impacted by chemicals?” says Walker, who also has expertise in clinical nutrition.
In this same cohort of infants in Spain, Walker has already discovered that babies’ gut microbiomes progress to a composition similar to adults earlier than what prior research had suggested, in many cases becoming adult-like as early as 9 months and coinciding with the introduction of solid foods.
Next, Walker aims to identify modifiers of the gut microbiome, in order to design interventions that may help reduce exposure and prevent disease.
“Microbiota should be considered a key aspect of nutrition research and treatment, and we’re not quite there yet,” he says.
Walker worked as a professional chef in New York for nearly seven years. He pivoted his career path to study nutrition and performance physiology, with the goal of working with elite athletes. But after his involvement in clinical metabolic and dietary research studies in obese adults and children, Walker changed his life’s mission.
“I didn’t want to spend my career getting ultra healthy people to improve by milliseconds,” he says. “I wanted to work with people who were sick.”