Ravinder Nagpal, MSc, Ph.D., an associate professor specializing in nutrition and the microbiome at Florida State University (FSU), helms The Gut Biome Lab, a research team that studies the role of nutrition in maintaining gut health and preventing or treating chronic disease. He serves on the editorial teams of several peer-reviewed medical journals, most notably as editor-in-chief of Gut Microbiome and Health and associate editor of Frontiers in Microbiomes and Frontiers in Nutrition.

Nagpal’s research is supported by numerous governmental agencies, commodity boards and industry associations, including the U.S. Department of Agriculture, Florida Department of Health, Infectious Diseases Society of America, U.S. Environmental Protection Agency, National Institutes of Health, The Institute for Successful Longevity at FSU, Academy of Nutrition and Dietetics, The Almond Board of California and The Peanut Institute.

 

How do you define the gut microbiome, and why is it important?

 

The gut microbiome is a very dense, complex community of various bacteria, fungi and protozoa that live in our gut during our entire life span. We are born with a very simple microbiome. My research has shown that when we come into this world, even on day one, our gut has some bacteria, but the microbiome is very simple, and the bacterial species that are there are acquired from our mom during birth or even before birth.

As we age, environmental exposures come into play. We acquire a lot of bacteria when we start to eat solid foods and as we are exposed to shared spaces, including siblings’ beds. By the time we are 2 or 3 years of age, our microbiome starts becoming very rich, with over 1,000 species of bacteria and fungi that impact our overall health by helping us to digest food, maintain good metabolism and regulate our intercellular immune system.

 

How does the gut microbiome impact our overall health?

 

Every now and then, we consume foods that are not sterile, but we don’t usually get sick from these foods when our native gut microbiome is strongly colonized, thus posing a resistance to invading pathogens from growing or establishing themselves in the gut. That competition for nutrients and for colonization in the gut protects us from invading pathogens making us sick.

The gut also has its own immune system called the enteric immune system, which is strongly modulated by the microbiome. Some studies in mouse and rat models have shown that if we eradicate the microbiome, the host becomes more prone to infection. Studies have also shown that when we remove the microbiome, the host’s nutrient absorption and metabolism slow down and aging speeds up.

Our studies also show that the microbiome is important for brain health because it produces many metabolites that can travel from the gut to the blood and then from the blood to the brain, acting as neurotransmitter signals that influence brain health. Anxiety issues, depressive symptoms, cognition and dementia-related issues are all strongly controlled by the microbiome.

We have a symbiotic relationship with our microbiome. We provide our microbiome shelter and physical space to thrive and grow, and the bacteria provide us a wide array of benefits. It affects digestion, metabolism, immunity and nervous system regulation. It regulates inflammation in the body and helps to produce numerous beneficial metabolites and short-chain fatty acids that are important for overall health.

 

How can we determine if we have a healthy microbiome?

 

The microbiome is very personalized. It varies from person to person, and within a person, the microbiome varies during the life span, depending on the diet, lifestyle habits, travel, medications, etc. If you go on vacation and your diet changes, the microbiome will change slightly, but it has a strong resilience and is able to come back to normal very quickly, provided we are eating healthy foods.

There is no gold standard, universal definition of a healthy microbiome. It is the one you carry when you are feeling healthy and fine. However, there are a few specific bacterial species that are known to be beneficial for everyone and some species that are known to be pathogenic for most or all.

When we do our research studies, we collect fecal samples from each subject and scan their entire microbial community. We identify the ratio of beneficial bacteria over opportunistic or pathogenic bacteria, noting any toxigenic or potentially pathogenic bacteria that are out of proportion, which would indicate a bad or unhealthy, misbalanced microbiome known as dysbiosis. We also want to know if certain beneficial or probiotic bacteria are missing or unusually low, which is also an indication of dysbiosis. Our findings are further validated with a thorough questionnaire about the person’s medical history and lifestyle.

There are various types of dysbiosis. It can be a depleted overall state due to antibiotics, overconsumption of alcohol or other drugs or medications. It can also be an unusually high presence of pathogenic bacteria. Or, it can involve both—some beneficial bacteria are lacking and then some pathogenic bacteria are thriving.

 

How can we maintain a healthy gut microbiome?

 

Many factors contribute to a good microbiome, including exercise, good sleep habits and a stress-free routine, but the most important factor is the food that we eat. We have thousands of species of bacteria, and each of those species has their own food preferences. The majority of the diet should be plant-based, including a diversity of fruits, vegetables, salads, minimally processed grains, legumes, nuts and seeds, so that we are nurturing all different types of bacteria. Make sure to include the macronutrients (carbohydrates, fats and proteins) and micronutrients (vitamins and minerals).

Avoid overeating and stay away from ultra-processed foods. Prioritize a nutrient-rich rather than calorie-rich diet, so, for example, have a raw orange or apple rather than fruit juice. Even 100 percent fruit juice eliminates many vitamins and functional components of the fruit during the processing steps. Make sure to consume an organic diet that is free from chemicals, additives, emulsifiers, pesticides and antibiotics.

Variety is super important. Eating the same exact diet, even if it’s made up of very healthy ingredients, is going to be boring and unsustainable. Eat different foods from all the food groups daily. Instead of eating an apple every day, introduce mandarins, half a banana, berries, avocado, watermelon or mango. Eat different types of salads and keep your protein varied from day to day to include fish, eggs, chicken, lean meat, chickpeas, legumes or peanut butter.

Fiber is important, but don’t concentrate on just one type of fiber. Different types of fiber support different types of beneficial bacteria, so we need to make sure that our diet is diverse. Include a good source of insoluble and soluble carbohydrates.

 

Do you recommend fermented foods every day?

 

If someone is a fan of yogurt, I would suggest they try different types. Maybe this week consume Activia and next week consume Yakult, or some Greek yogurt, some days kombucha, some days kimchi or kefir. Each fermented food will aid its own probiotic bacteria, so you don’t want people to stick to one for a very long time because that can sometimes lead to disturbances in the gut microbiome community due to selective over-colonization. We want diversity of fermented foods, as well as diversity of prebiotics. Of the many recommended foods, we believe a little bit of everything is the best way to go.

 

Do you recommend taking probiotic or prebiotic supplements?

 

As long as someone is healthy, they don’t really need probiotic supplements. You already carry your own beneficial probiotics; just nurture them by eating a healthy diet. Probiotics in the U.S. are sold as food supplements, which means that they are not required to be clinically tested and validated, so we may not know if they are actually going to be really effective.

If someone is suffering from an immune condition or a digestive issue, a probiotic supplement might be recommended by a physician. Different species and strains of probiotics have different functions and behaviors in the gut, but we need to do a lot of research before we can say which species are the ideal probiotics for certain conditions.

Prebiotics, defined as food components like fiber and resistant starches, as well as fermented foods and vegetables, are more effective than commercial probiotic supplements because they feed the indigenous population of beneficial and commensal [neither harmful nor beneficial] bacteria. Better to just focus on a healthy diet from plant-based food sources that provide natural prebiotics to foster a healthy microbiome.

 

What is the current focus of your research?

 

We are conducting multiple clinical studies to determine the role of the microbiome in metabolic conditions such as obesity and Type 2 diabetes, and in neurodegenerative disorders, including Alzheimer’s disease and related dementias. We are also working to develop nutritional interventions to improve cardiometabolic and neurodegenerative health. Specifically, we are investigating how certain components in our diet, including dietary fiber, resistant starches, nuts, fruits and polyphenols, modulate the gut microbiome, and how these diet-biome interactions influence gut, metabolic and neurological health.

 

What discoveries have you recently made in The Gut Biome Lab?

 

For decades, Alzheimer’s disease and related dementias were believed to originate exclusively within the brain, driven by the impaired functioning of neurons and proteins, as well as plaque buildup. However, our recent research has revealed that older adults with mild cognitive impairment who are at risk for Alzheimer’s harbor a distinct gut microbiome compared to healthy individuals, indicating that gut health could be both a marker and a modifiable risk factor in disease progression. This discovery may facilitate novel avenues for prevention and management, including dietary and lifestyle changes to restore microbiome homeostasis to support neurocognitive health.

Our research has also discovered that obesity can heighten a predisposition to cognitive decline via alterations in gut-microbiome-brain signaling, a mechanism that has been largely under-explored in aging populations. This highlights the gut-muscle-brain axis as a modifiable target to enhance cognitive health in aging populations. Our nutrition studies have shown how small changes in dietary habits, such as prudent snacking and the incorporation of almonds, chickpeas and lentils in the diet, could induce considerable improvements in our gut microbiome function, which can further improve cardiometabolic and systemic health.

 

Sandra Yeyati is national editor of Natural Awakenings.

Related Articles: