How Prebiotics, Probiotics, and Postbiotics Help Maintain a Healthy Gut

Why a good gut means good health.

Author: Tina Reilly
A male patient stands in the kitchen of his household at Hebrew Rehabilitation Center in Boston. A female member of the culinary team stands next to him, holding a green pepper. In front of them there are a variety of colorful fruits and vegetables on the counter. They are looking at each other and smiling.

There’s been a lot of buzz in recent years about probiotics and their role in promoting good health. Many people are turning to them to prevent or treat a myriad of ailments, and probiotic products are proliferating on grocery and pharmacy shelves. Friends share their success stories, and manufacturers tout their product benefits. In fact, the International Scientific Association for Probiotics and Prebiotics estimates product development and sales will reach $50 billion within the next five years.

But how much do you really know about probiotics – what they are and how they maintain or improve health – let alone prebiotics and now postbiotics?

As Clinical Nutrition Manager at Hebrew Rehabilitation Center in Boston and Dedham, this is a topic that I love. Let’s start by looking at the gut.

What is the gut and why is it so important?

We’re all familiar with the saying “you are what you eat.” And what you “are” includes trillions of micro-organisms that live in what is commonly referred to as your gut. Made up mostly of bacteria they create a micro-ecosystem called the microbiome, which plays an important role in your health.

When you consider what makes up the gut it’s easy to see why a good gut is pivotal to good health. The gut is the gastrointestinal system, also known as the gastrointestinal tract, digestive system, or digestive tract, and is made up of a group of organs that includes the:

  • Mouth
  • Esophagus
  • Stomach
  • Pancreas
  • Liver
  • Gallbladder
  • Small and large intestines
  • Colon
  • Rectum

The gut serves many essential roles in sustaining and protecting the overall health and wellness of your body starting with the intake and absorption of nutrients and water.

A stable gut microbiome protects us against invading harmful microorganisms and helps regulate our immune system. When things like changes in diet, antibiotic use, age, or infection disrupt the gut microbiome, a range of inflammatory, pathogenic, and metabolic conditions such as inflammatory bowel diseases and colorectal cancer can result. Dysbiosis – which is when there are too few beneficial bacteria and an overgrowth of bad bacteria – is found in various chronic diseases such as diabetes, obesity, and cardiovascular disease.   

The theory goes that prebiotics, probiotics, and now postbiotics can all contribute to keeping your gut in top working order. But what are they and how do they help? Let’s start with the most familiar term, and perhaps easiest to understand – probiotics.

What are probiotics?

The term probiotic is derived from the Latin preposition “pro,” which means “for” and the Greek word “biotic” meaning “life.”

Although people often think of bacteria and other microorganisms as harmful “germs,” many are actually helpful. Some bacteria help digest food, destroy disease-causing cells, or produce vitamins. Many of the microorganisms in probiotic products are the same as or similar to microorganisms that naturally live in our bodies.

Microbes must have three characteristics to fit the definition of a probiotic: 

  1. They must be living
  2. They must offer a scientifically substantiated health benefit 
  3. They must be consumed in adequate amounts to produce that health benefit

Probiotic foods and products contain live organisms, including bacteria and yeasts that are intended to have health benefits when consumed or applied to the body. They can be found in yogurt and other fermented foods, dietary supplements, and beauty products. 

Common fermented foods that naturally contain probiotics, or have probiotics added to them, include: 

  • Yogurt
  • Kefir
  • Kombucha
  • Sauerkraut
  • Pickles
  • Miso
  • Tempeh
  • Kimchi
  • sourdough bread
  • some cheeses

What are prebiotics?

Prebiotics essentially feed probiotics. A prebiotic is defined as a nondigestible food ingredient that promotes the growth of beneficial microorganisms like bacteria and fungi in the intestines. They come primarily from dietary fiber that we’re unable to digest, and the beneficial bacteria in your gut eat this fiber. 

Sources of prebiotics include:

  • Whole grains
  • Bananas
  • Greens
  • Onions
  • Garlic
  • Soybeans 
  • Artichokes
  • Dietary supplements

What are postbiotics?

Postbiotics are byproducts of the fermentation process carried out by probiotics in the intestine. In other words, as probiotics feed on prebiotics, postbiotics are produced. Postbiotics are like probiotic waste, but with health benefits.

Because postbiotics are a byproduct of probiotic fermentation, the direct source of postbiotics are probiotics. Foods that can help increase the concentration of postbiotics in the gut are:

  • Yogurt
  • Sauerkraut
  • Miso soup
  • Soft Cheeses
  • Kefir
  • Sourdough bread
  • Buttermilk
  • Pickles
  • Tempeh

Additionally, postbiotics can be produced and extracted in laboratories to be used for therapeutic purposes, and delivered through pills and direct application.

To recap, prebiotics promote the growth of probiotics, which produces postbiotics.

Are probiotics effective and safe? What does the research show?

Few treatments for human diseases have received as much investigation in the past 20 years as probiotics. In 2019 alone PubMed, an online catalogue of science and biomedical research maintained by the United States National Library of Medicine at the National Institutes of Health, recorded 792 clinical trials for probiotic treatments of human conditions. 

Much of the research is promising and shows that probiotics and prebiotics are useful in preventing certain disease conditions as well as possibly promoting specific aspects of health. 

For older people both probiotics and prebiotics may be helpful in treating malnutrition, particularly in lactose intolerance and calcium absorption, and in constipation. Probiotics have also been shown to boost immunity.

But research also reveals a dark side to probiotic enthusiasm. In recent years, multiple systemic reviews, meta-analyses, and expert opinions criticized claims of probiotics’ effects and safety. Critics point out problematic research design, incomplete reporting, lack of transparency, and under-reported safety. There seems to be a consensus in the medical research community that more studies are needed to establish in what cases disease treatment with probiotics is useful and safe.

The bottom line – be a smart consumer

Probiotics are generally considered safe — they're already present in a normal digestive system — although there's a theoretical risk for people with impaired immune function. Make sure the ingredients on any product claiming to be probiotic are clearly marked on the label and familiar to you or your health provider. 

Keep these tips in mind regarding prebiotic and probiotic consumption:

  • Don’t use probiotics as a reason to postpone seeing your health care provider about any health problem.
  • Adding more foods that contain natural probiotics and prebiotics – like whole grains, yogurt, and leafy greens – is great for your overall health, not just your gut. 
  • If you’re considering a probiotic dietary supplement, consult your health care provider first. This is especially important if you have health problems. Anyone with a serious underlying health condition should be monitored closely while taking probiotics.
  • When buying supplements, check the label carefully to make sure it contains “live and active cultures.” A general rule is to choose products containing at least 1 billion colony forming units, or CFUs, although dosing guidelines to treat or prevent certain conditions have yet to be fully established. Be sure to store your supplements in the refrigerator to preserve their freshness and potency.
  • Talk with your health care providers about any complementary health approaches you use. Together, you can make shared, well-informed decisions.

At Hebrew Rehabilitation Center, part of our approach to patient-centered care is to tailor each person’s diet to their nutritional needs as well as to their likes and dislikes. Every patient has their own nutrition plan – some may need a low-salt diet; others may need a gluten-free diet – but we always make sure each person is eating a variety of healthy and delicious foods. If you or a loved one require more care than can safely be provided at home, we’re here to help. Call us at 617-363-8372 or contact us online

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Hebrew Rehabilitation Center

Hebrew Rehabilitation Center provides skilled care and support after illness or surgery and offers long-term chronic care and specialized care for those with memory loss.

A patient at Hebrew Rehabilitation Center listens to therapeutic music with the help of a life enhancement team member.

About Tina Reilly

Clinical Nutrition Manager at Hebrew Rehabilitation Center

Tina Reilly is the Clinical Nutrition Manager at Hebrew Rehabilitation Center. Previous to this position, Tina was the Director of Food and Nutrition Services at Kindred Hospital, Boston. Her experience includes being a dietician at several Boston hospitals, including Beth...

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