The human body, and mainly the digestive tract, is home to trillions of microorganisms. Bacteria, fungi and viruses, as well as the less known archaea and protozoa, all live side by side in our gut. These tiny living organisms, collectively known as the gut microbiota, can have a great impact on our health and well-being. Over the past few decades, researchers have been investigating how we can influence our gut microbiota through diet.

Prebiotics are non-digestible fibers that act as food for microorganisms, promoting their growth and activity. Probiotics on the other hand, are living microorganisms that, when consumed in adequate amounts, can provide health benefits. In simpler terms, prebiotics are the food source for our gut bacteria, while probiotics are the live bacteria that offer health benefits when consumed.

Your large intestine contains 100 trillion “good” bacteria that are essential to health. Called the microbiome, these beneficial microbes help maintain healthy bowel function, and may even help with conditions like inflammatory bowel disease. Research suggests they may even play a role in regulating weight and mood.

Everyone starts with their own unique microbiome at birth. We add to these through the foods we eat. Here are some of the best ways to add healthful bacteria to your microbiome:

• Yogurt and kefir. Be sure to look for the words “live and active cultures” on the label to make sure you are getting live cultures.
• Fermented foods. Beneficial microbes are the “cooks” for some familiar foods. For example, they turn cabbage into sauerkraut, cucumbers into sour pickles, soybeans into miso, and sweetened tea into kombucha. When the products have been pasteurized — as most packaged fermented foods are — the microbes will be dead. The best solution is to buy from delis where they do the pickling themselves, or natural food stores that carry fermented foods. Or make your own; you can find clear and easy instructions in books and online.

You can help your body produce healthy gut bacteria. Here’s how:

• Include plenty of foods rich in insoluble fiber, which tend to contain the most prebiotics. You’ll find them whole-grain products such as oatmeal and whole-grain breads, as well as in vegetables like asparagus, leeks, onions, and garlic, and starchy vegetables like sweet potatoes and corn. Beans, lentils, and peas are also good sources.
• Limit sugar, saturated fat, and processed foods. These can deplete the good bacteria in the gut. As always, try to stick with whole, unprocessed foods.

How they affect our health?

Prebiotics are non-digestible food components, such as certain dietary fibers. Once they arrive in the intestine, they become food for beneficial microorganisms in the gut and are broken down into chemicals that stimulate their growth and activity. By eating a variety of prebiotic foods, we can feed the beneficial microorganisms in our gut, helping to create a healthier and more diverse microbiota. This can lead to better intestinal health and metabolism and also help prevent harmful bacteria (“pathogens”) from growing in our gut.

Even though the term prebiotics encompasses a broad range of compounds, they all contribute to good digestive health. Some functions of prebiotics include supporting nutrient metabolism and regulation of our immune system, and influencing our disease risk. Prebiotics boost the production of health-promoting substances like short-chain fatty acids (SCFAs), that have been linked to reduced risk of colorectal cancer. Evidence suggests that prebiotics also help with constipation by promoting more regular, frequent and well-formed bowel movements.

Probiotics are microorganisms that can benefit our health in many different ways. There are seven commonly used types of probiotic microorganisms: Lactobacillus, Bifidobacterium, Saccharomyces, Streptococcus, Enterococcus, Escherichia, and Bacillus. Each of these also consists of dozens of strains which can positively affect the gut microbiota, boost the immune system or have other health benefits. However, it’s important to remember that the effects of each probiotic strain are unique and can vary based on the amount consumed and that research into these understanding these effects is still in early stages.

To be considered a probiotic, a food or product should contain a specific minimum amount of microorganisms, the so-called colony-forming units (CFU), for its claimed health benefit. For example, consuming yoghurt with at least 108 CFU of living Lactobacillus delbrueckii subsp. bulgaricus and Streptococcus thermophilus bacteria, commonly used microorganisms as yoghurt starter cultures, has been found to improve digestion of lactose in people with lactose maldigestion.

Some probiotic strains might also help improve symptoms of diseases such as ulcerative colitis or irritable bowel syndrome, and regular consumption of probiotics has been shown to lower the likelihood of upper respiratory tract infections like the common cold. Probiotics are also used to lower the risk of antibiotic-associated diarrhea.

Which foods contain most probiotics and prebiotics?

Some of the most popular foods with probiotics are fermented foods. This means that they have live cultures, or live beneficial bacteria strains, that either naturally occur or are added during production. 

Some examples include:

• Dairy: yogurt, kefir, certain cheeses (gouda, Swiss, parmesan, cheddar)
• Non-dairy: yogurt, kefir (check the packaging for added bacteria before purchasing)
• Vegetables: sauerkraut, kimchi, other pickled vegetables 
• Soy products: tempeh, miso, natto
• Beverages: fermented drinks such as kombucha 

Some of these foods are thought to be synbiotic, meaning that they contain both prebiotic and probiotic bacteria. These include certain dairy and non-dairy yogurts and kefir, as well as certain pickled vegetables.

Many of the most common prebiotics are found or derived from foods we eat. Fiber is the unsung hero of a healthy diet and digestive system, and many prebiotics are types of fiber.  Foods that are high in prebiotics include:

• Legumes: beans, peas, chickpeas 
• Cereals and whole grains: oats, bran, barley, rye 
• Fruits: bananas, berries, grapefruit, olives (and extra-virgin olive oil)
• Vegetables: garlic, leeks, onions
• Nuts and seeds: flaxseeds, pistachios, almonds 

There are several possible benefits of regularly taking probiotics. Probiotics may help with:

• Better working of the immune system
• Lower cholesterol levels when used with other cholesterol-lowering therapies
• Supporting blood sugar control and insulin release when used with other therapies
• Lower risk of developing eczema in childhood
• Reducing the risk of yeast infections

Probiotics may also help your gut microbiome recover after an illness, like gastroenteritis. 

Prebiotics may have some potential health benefits like:

• Improved mood and memory
• Lowering overall inflammation
• Supporting a healthy immune system

Even though we all need to support our gut, we do not want to push it too far. Certain supplements could lead to unwanted side effects. Everyone is different, so a supplement that may work for you may not have the same effect on your family member or friend. 

Some possible side effects include:

• Digestive issues: including gas, bloating, indigestion, nausea
• Headaches: from amines in probiotic foods 
• Allergic or sensitivity reactions: especially to added ingredients in supplements

It’s worth noting that probiotics may be riskier in people who are immunocompromised or who have severe illnesses. 

How to improve your gut health?

Although many may think of the stomach, your “gut” refers to your small and large intestines. Within your gut lives a whole community of microorganisms, like bacteria, fungi and viruses – this is called the microbiome.

When your gut is healthy, you have more good bacteria than harmful bacteria in your gastrointestinal (GI) tract. And this is important, because a healthy gut can help you digest food, metabolize nutrients and reduce inflammation. Studies also suggest that a healthy gut may positively affect heart health (for example, by lowering blood pressure), mental health and kidney function.

Your gut is a complex habitat for over 1,000 different species of bacteria. What’s important is keeping all these microbes balanced, so you have more healthy ones than harmful ones. While prebiotics and probiotics could be a good way for you to maintain your gut health, there are other ways you can promote a balanced microbiome:

• Maintain a fiber-rich, diverse diet. The more types of food you eat, the more diverse your microbiome becomes. A well-rounded diet can help feed all the different species of bacteria in your GI tract. Focus on high-fiber fruits and vegetables, like raspberries, artichokes, beans, lentils and whole, unprocessed grains.
• Get good, regular sleep. When you don’t get enough sleep, your stress levels are more likely to increase. And often, this stress can impact your gut, changing the makeup of your microbiome. Once that bacterium is compromised, it can start to impact your quality of sleep and even your brain function. Aim for 7-8 hours of sleep per night and establish a regular bedtime routine.
• Exercise consistently. Studies suggest that regular exercise can positively affect gut health. Regular physical activity encourages healthy digestion and may increase levels of beneficial microbes in your gut, which can boost both your metabolism as well as your immune system. If you’re not someone who frequently exercises, don’t worry – you can start small. Just 30 minutes of light activity like walking or water aerobics a few times a week can make all the difference.
• Manage your stress levels. As mentioned before, stress can wreak havoc on your gut. In fact, we often say that the gut has its own brain. Many of the microbes in your intestines can impact brain function and increase your likelihood of experiencing anxiety, depression and sleep issues. When you’re too stressed, you put the healthy bacteria in your gut at risk, threatening the balance of your microbiome.

When you don’t consume enough probiotics and prebiotics in your diet, your digestive system will not function as it should. This can lead to a variety of symptoms, including:

• Gas
• Bloating
• Diarrhea
• Constipation
• Sugar cravings
• Skin breakouts
• Frequent illnesses

Prebiotics and probiotics are helpful for promoting a diverse and thriving gut microbiome. Not only can they promote gut health, they may also improve immune health, mental health, and improve absorption of certain micro-nutrients.