Nutrition Bytes Podcast with Gelson's Registered Dietitian Jessica Siegel


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Today I‘m going to talk about a topic that I’ve been following for a few years and I think we finally know enough about to make some useful dietary recommendations. I’m going to tell you about the care and feeding of your good bacteria.


Believe it or not, the bacteria in your gut could hold the key to your health. There are over 100 trillion microbes living on us and inside us and they can influence factors as far reaching as appetite, mood, and even mental health. I have been fascinated for the last few years with this emerging area of research into what is called the human microbiota, or microbiome.


The terms microbiota and microbiome may be unfamiliar to a lot of listeners, so before I go any further, I want to explain them.


The human gut microbiota is defined as the trillions of microscopic organisms (including bacteria, viruses, and fungi) –some good and some bad – living in the digestive tract of the human body. And the microbiome is the whole community of microbes, or the collective “genome” of the microbiota (bacteria have genes, too!). There are usually over 1,000 different species of microbes in this diverse community, which used to be referred to as “flora”. Normally, the bacteria live in harmony with the human body and are, in fact, essential to human survival.


By some estimates, we have more than three times the number of microbial cells in our bodies than we do human cells – in a way, we are more microbial than human! – though our collective microbiota only weighs about two and a half pounds.


Humans’ microbiomes have evolved over thousands of years, but they seem to have changed significantly over the last few decades, which some researchers believe has contributed to the rise in autoimmune diseases, food allergies, asthma, and even obesity. They attribute this striking change to a handful of lifestyle factors, including a diet comprised of highly processed, industrialized food, aka the “Western Diet,” and an overly clean and sanitized environment that overuses antibiotics and antibacterial products.


You’re probably wondering why I’m telling you all this? Well, I know the beginning of the year is the time that most people shift their focus from holiday eating to losing weight and eating better. Instead of putting yourself on a restrictive eating plan or a fad diet, I want listeners to instead focus on gut goodness. Set your sights on promoting the balance and diversity of your gut bacteria to influence your weight and health.


Our microbiota can influence:

  • Our immune systems
  • Inflammation
  • Moods and behavior
  • Aging
  • Diabetes, metabolic syndrome
  • Obesity and weight loss
  • Cancer risk
  • Digestive health and regularity
  • How well we absorb nutrients from our food
  • And even susceptibility to allergies


I’m not going to discuss the relationship between the microbiome and each of these aspects of health, but I will say that on a basic level, it’s probably easy to see how having a strong and diverse microbiome can keep you healthy by fighting off pathogens that you might eat or swallow and also how it can keep your digestive tract healthy. On a much more complex level, the microbial composition of the gut can affect parts of our bodies as far away as the brain! The gut microbiome can influence how our brain processes behaviors related to stress, mood, pain, and cognition in conditions such as depression, obsessive compulsive disorder, and anxiety. How fascinating is that?


Suffice it to say that all of the ways our microbiome has the potential to influence our health is extremely complex and still very much unknown. In some instances, our microbiome may influence the onset of disease while, in others, disease may be altering our microbiomes. Either way, many researchers believe that promoting balance in our individual gut bacteria may be an important way to prevent or treat an amazing array of conditions and diseases.


Ok, by now I hope I’ve convinced you that you should be thinking about how to influence your microbiome in order to improve your health. Here’s how you can achieve and Maintain Microbial Balance:


First, let me tell you what not to do!


Poor nutrition (especially, a high fat diet, a high sugar diet or a low-fiber diet) is terrible for your microbiota! Also, antibiotics, stress, inflammation, and a few other factors can negatively affect the diversity and robustness of our microbiota. We all encounter at least one of these issues sporadically in our lifetimes and in reality, it’s just part of life—sometimes you have no choice but to take an antibiotic and life can be very stressful at times. That’s why having a resilient bacterial community in place to help protect our microbiome from undesirable, lasting changes is important for our long-term health.


The best way to influence your microbiota is through diet. We know that eating patterns can impact bacterial diversity. Plant-based diets, such as the Mediterranean Diet, as well as vegetarian and vegan diets are best for encouraging a good bacterial population that produces anti-inflammatory substances called short chain fatty acids (SCFAs). People whose diets consist of mostly vegetables, fruits, beans, legumes, and grains tend to have well-balanced microbiomes. These eating patterns are also associated with good overall health and lower rates of heart disease, diabetes, certain cancers, overweight, and obesity. As most of my listeners already know, I recommend the Mediterranean Diet as the best framework for healthful eating. It emphasizes two vegetarian meals a day and extra virgin olive oil as its main fat, but is flexible so that fish, poultry, and meat can be eaten weekly. It is an enjoyable diet and most people are successful with this eating pattern because of its flexibility. You can change your microbiota quickly by changing your diet, but maintaining those changes for the long-term will be the key to life-long health benefits.


There are three specific dietary factors that can alter your microbiome: (1) Fiber, (2) Probiotic foods and possibly supplements, and (3) Animal flesh and saturated fat.


Dietary fiber plays a key role in influencing and nourishing your gut bacteria. Specific types of fiber that are only digestible in the large intestine are called prebiotics, and these are the desirable types for growing our good bacteria. (Other types of fiber are good for other purposes, so don’t exclude them simply because they don’t have prebiotic properties.) Naturally fiber-rich foods, such as vegetables, fruits, beans, legumes, nuts, seeds, and grains, provide nourishment for gut bacteria to flourish. When our gut bacteria ferment the fibers in these foods, they produce desirable SCFAs that promote the microbial diversity we are seeking to help prevent inflammation and chronic diseases. Our goal should be to eat a wide variety of naturally fiber-rich foods (not fiber-enriched processed foods). The average American who eats a typical Western Diet that is high in processed and refined packaged foods and low in fruits, vegetables, and whole grains consumes about 15 grams of dietary fiber a day, while our goal should be between 25 to 38 grams of fiber a day depending on age and sex. If you’re not currently eating a lot of fiber, it’s important to increase the amount of fiber in your diet slowly to prevent gas and bloating. You also need to increase the amount of water you drink as you up your fiber intake. Approach this fiber increase seriously, since if you develop gas and bloating by increasing your fiber too quickly, you may be more likely to give up on this important endeavor.


Probiotics are good microbes that we can eat or take in supplement form to help introduce new species of microbes into our systems. Probiotic foods are important for supporting bacterial diversity in our microbiomes. They are found in cultured foods such as yogurt, kefir that say “live and active cultures” on the package, and in lower concentrations in cultured foods such as Kombucha, cultured butter, buttermilk, and cultured cheeses like cream cheese and crème fraiche. Probiotics are also found in fermented foods like unpasteurized sauerkraut, pickles, and kimchi, and miso, tempeh and sourdough bread. A list of probiotic foods and a listing of specific foods at Gelson’s that contain live and active cultures can both be found on the show notes page at Try to eat at least one probiotic food daily, but experiment with different foods and even brands of yogurt and kefir to see which strains of bacteria make you feel your best. If eating fermented foods on a regular basis is not possible, consider a probiotic supplement, especially if you are taking antibiotics. Please keep in mind that the research in this area is still very young and we need more studies to confirm what certain strains and brands of probiotic supplements can—and can’t--do for us. These recommendations are general and are intended for healthy adults; individuals with compromised immune systems and those undergoing cancer treatment should not take probiotic supplements. Everyone should consult with their physician before beginning to take a probiotic supplement.


Finally, consider the dietary factors you need to minimize in order to nourish your microbiome. Red meat (from beef, pork, and lamb) contains a nutrient that certain bacteria break down into a dangerous substance that can increase the risk of heart attacks and strokes. Eating red meat up to once a week (as is recommended on the Mediterranean Diet) should not be problematic, so long as you are also eating a mostly plant-based diet. Eating red meat regularly, however, can be unhealthy for your microbiome and your heart. Additionally, saturated fat from animal flesh sources such as fatty steaks and chicken skin, can be problematic for our microbiome. Eating significant amounts of saturated animal fats as part of your regular diet (as is common in a typical Western Diet) can reduce the diversity of gut bacteria and may encourage the proliferation of bacteria that are associated with inflammation and obesity. Eating a mostly plant-based diet that contains high-quality carbohydrates most of the time will allow room for an occasional steak or hamburger without disrupting the homeostasis of your microbiota.


The microbiome is a fascinating area of study that has the potential to reveal many new ways to influence our health and even treat diseases. We are still a long way off from knowing what that each person’s right balance of bacteria is, BUT there are ways to influence the balance and diversity of the bacteria in our guts through our diets, lifestyles, and environments. Changing these factors has the potential to improve our general health and wellness. Additionally, what we do know about eating to promote the diversity of the vast ecosystem that lives in our guts is in line with another significant dietary recommendation to support overall health: eat a plant-based diet like the Mediterranean Diet. To learn more about the Mediterranean Diet, download my first few Nutrition Bytes podcast or pick up a copy of my Healthy Living Guide at your local Gelson’s. Wishing you a happy, healthy, and (good) bacteria-filled new year!




Q: can you talk more about specific foods that are good for our gut bacteria?

A: So, I talked about the importance of eating fiber-rich foods for feeding our bacteria, but there are some specific foods that are really nourishing: Vegetables: Jerusalem artichokes, chicory, garlic, onion, leek, shallots, spring onion, asparagus, beetroot, fennel bulb, green peas, snow peas, sweetcorn, savoy cabbage, and mushrooms Legumes Chickpeas, lentils, red kidney beans, baked beans, soybeans 

Fruit: Cherimoyas, nectarines, white peaches, persimmon, watermelon, grapefruit, pomegranate. 

Dried fruit (e.g. Prunes, dates, figs) Bread / cereals / snacks Barley, rye bread, rye crackers, pasta, gnocchi, couscous, wheat bran, wheat bread, oats Nuts and seeds Cashews, pistachio nuts 

Other: Human breast milk



Mediterranean Chicken 

Banana Walnut Oatmeal