Prebiotics, Probiotics & Postbiotics: Your Complete Guide

Probiotics are live, non-infectious microorganisms (bacteria and yeasts) that provide a wide variety of health benefits. Indeed, the term “probiotic” is derived from a pair of Latin and Greek words - “pro” and “bio” - that together mean “for life.” (3).

Naturally found in yogurt, sauerkraut, and other fermented foods, probiotics are also added to foods such as juices, nutrition bars, and cereals. Probiotic supplements may contain a single bacterium or several different microorganisms. Common strains of probiotics include Bifidobacterium and Lactobacillus while Saccharomyces boulardii is a common yeast strain (4).

Probiotic supplements must be able to circumvent the harsh acidic environment of the digestive tract in order to reach and colonize the colon, the primary residence of the gut microbiota. This is achieved through effective delivery systems and strategies such as freeze-drying the microbes and the use of enteric-coated capsules that resist stomach acid degradation (1).

In the body, probiotics function in a variety of ways (1). These beneficial microbes:

• May help improve the composition and diversity of the gut flora
• Potentially boost the immune system, possibly resulting in a balance between pro- and anti-inflammatory effects as well as immune tolerance (i.e., the ability to distinguish between harmful and harmless chemicals or antigens)
• Likely reduce the permeability of the intestinal barrier walls to toxic chemicals and infectious microbes (i.e., a “leaky gut”) by potentially strengthening the integrity of the cells lining the gut
• Produce compounds including antibacterial proteins and short-chain fatty acids (SCFAs) which may potentially help suppress inflammation
• Help block the growth and activity of harmful bacteria and viruses in the gut
• Help stimulate production of protective mucus
• Possibly regulate the transit of food through the digestive tract

Probiotics may be used to help with a myriad of conditions. Some examples supported by strong research evidence include the following disorders:

Intestinal Diseases

Disorders involving the gastrointestinal tract (GI) are often linked to a disruption in the balance of the gut bacteria. These conditions include antibiotic-associated diarrhea, ulcers, inflammatory bowel disease (IBD), irritable bowel syndrome (IBS), lactose intolerance, and even GI cancers (3).

By increasing the richness and diversity of the gut flora, probiotics can be harnessed to potentially help alleviate intestinal disorders. Additionally, probiotics may help manage these conditions through their ability to potentially improve immune function, increase production of digestive enzymes (e.g., lactase to digest lactose), and help heal a “leaky gut” (decrease intestinal permeability) (3).

Allergies & Allergic Diseases

The gut microbiota interacts with the immune system to promote and maintain tolerance (unresponsiveness) to food allergens while also mounting an immune response to foreign antigens (e.g., pollen, bacteria, chemicals). Dysbiosis—changes in the composition of the gut microbiota—can lead to loss of immune tolerance and increased risk of allergic diseases (5).

Two systematic reviews of controlled clinical trials have concluded that supplementation with probiotics before and after birth may potentially prevent eczema and other allergic diseases (6, 7). Strong evidence from animal studies also supports the use of probiotics in the treatment of allergic diseases (8).

Among the mechanisms that underlie the anti-allergic effects of probiotics are production of anti-inflammatory proteins, potentially healing a leaky gut, and possibly balancing immune responses (3).

High Cholesterol Levels

Probiotics may help lower serum cholesterol levels directly by potentially inhibiting the body’s production of cholesterol and also by possibly reducing the absorption of cholesterol from foods. Indirectly, probiotics may help lower cholesterol by potentially causing increased elimination of bile from the body. This may result in more cholesterol being drawn from the blood to make more bile, thus potentially lowering blood levels (3).

Both human and animal studies suggest that specific probiotic strains (e.g., Lactobacillus, Bifidobacteria, and L. plantarum) may significantly decrease total cholesterol levels (3).

Cancer

The benefits of probiotics may even include the possible prevention and treatment of various types of cancer, including breast, lung, and colorectal cancers (9). For example, the probiotic strain Lactobacillus casei may degrade powerful carcinogens known as HCAs (heterocyclic amines) which are formed when meat or fish is charred and overcooked. These chemicals can cause genetic mutations and are linked to cancers of the stomach and colon (10).

Beyond cancer prevention, probiotics may be used as a potential adjuvant (supplemental) therapy in cancer treatment. Experimental studies suggest that probiotics may possibly reduce the formation, growth, and metastasis (spreading) of tumors while also potentially causing programmed cancer cell death (a form of “cellular suicide”) (9).

Probiotics may also potentially enhance the cancer-killing effects of chemotherapy drugs such as cisplatin. By potentially improving the gut microbiota, these beneficial bacteria may possibly decrease the severity of side effects (e.g., diarrhea) as well. Many of the potential anti-cancer effects of probiotics are due in part to their possible anti-inflammatory and immune-enhancing activity (9).

Obesity

It’s established that the gut microbiota of thin people differs from that of overweight or obese people. Thus, the use of probiotics to favorably alter the composition of the gut microbiota may be a potential therapy for treating excess weight and obesity (11).

In a recent review of clinical trials in overweight/obese individuals, significant weight loss was achieved in close to 70% of the studies through the use of probiotics. A trend in preventing weight gain was also observed. Combinations of a variety of strains (rather than single strains) of Bifidobacterium and Lactobacillus were found to potentially produce superior results (11).

Nevertheless, there is a lack of consensus in the medical literature, as other studies showed no effect from probiotics for weight loss (4).

Other Conditions

Besides obesity, probiotics may potentially help prevent and treat other metabolic disorders such as type 2 diabetes and non-alcoholic fatty liver disease (NAFLD) (12). They may also possibly aid in the prevention of dental caries and urinary tract infections (UTIs) (13).

Prebiotics are dietary substances that selectively promote the growth and activity of beneficial bacteria in the digestive tract. In other words, prebiotics function as “food” that is gobbled up by the good microbes in the gut, helping them to flourish and multiply (14).

Soluble fibers such as inulin, fructooligosaccharides (FOS), and galactooligosaccharides (GOS) are among the more common types of prebiotics. Good food sources of prebiotic fibers include bananas, garlic, onions, asparagus, and chicory root (14). Green bananas and legumes contain resistant starch, another type of prebiotic (15). Plant pigments known as polyphenols can also act as prebiotics. These antioxidant pigments are primarily found in fruits, vegetables, tea, and coffee (16).

Since prebiotics are typically non-digestible, they escape digestion in the small intestine and reach the colon intact. In the colon, bacteria ferment the prebiotics into short-chain fatty acids (SCFAs) such as butyrate, acetate, and propionate. These SCFAs play an important role in gut health by serving as a major fuel source for colon cells and by suppressing intestinal inflammation and the growth of harmful microbes in the gut (14).

The use of prebiotics may promote a greater abundance of good bacteria (e.g., Lactobacilli and Bifidobacteria) and help reduce numbers of harmful bacteria, potentially resulting in a more balanced and healthier gut microbiota (14). Thus, like probiotics, prebiotics may potentially improve the composition and diversity of the gut microbiota.

That being the case, it follows that prebiotics may be used to potentially help prevent and treat the same disorders that benefit from the use of probiotics. These conditions include gastrointestinal diseases (e.g., IBS, IBD) and various metabolic disorders such as obesity, type 2 diabetes, and non-alcoholic fatty liver disease (NAFLD) (12, 14).

Native Note: Dietary supplements that contain both probiotics and prebiotics are known as synbiotics.

While probiotics and prebiotics are familiar terms to many health-conscious people, there’s a new kid on the block: postbiotics.

So, what are postbiotics?

Postbiotics are by-products formed primarily during the fermentation of beneficial probiotic bacteria or yeasts. Among the wide range of molecules that can make up a postbiotic supplement are various proteins, vitamins (e.g, folate, vitamin K), enzymes, polyphenols, and short-chain fatty acids (SCFAs) (17).

Postbiotic supplements often consist of the products from bacterial/yeast digestion together with the non-living organisms that produce them. For example, ‘yeast fermentate’ is a postbiotic that includes both vitamins and other compounds created from yeast fermentation along with the yeast cells themselves, though no longer alive (18).

The absence of live organisms in postbiotics confers some advantages over probiotics. These include a longer shelf life, greater stability, and easier storage (17).

Postbiotics may be responsible for many of the potential health benefits of probiotics via their possible immune enhancing, antioxidant, anti-inflammatory, anticancer, and antimicrobial activity. They may potentially be used to help prevent or treat a number of diseases, including those with unknown causes (e.g., Alzheimer’s disease, inflammatory bowel disease, and multiple sclerosis) (19).

Butyrate is one of the most popular postbiotic supplements, and for good reason. As one of the short-chain fatty acids produced by beneficial gut bacteria, butyrate is well recognized for its potential role as a key energy source for the cells lining the intestinal tract. As such, it may help intestinal cells repair and renew themselves, potentially strengthening the barrier function of the gut wall in keeping foreign chemicals and invaders from entering the body (19).

Moreover, a review of studies suggests butyrate may help protect against potential atherosclerosis (plaque buildup in the arteries). In one study, butyrate generated from the bacterial digestion of high-fiber foods was shown to potentially reduce the size of arterial plaques in mice (20).

Native Note: Interestingly, you can also get butyrate from eating good old butter (NOT margarine), from which it derives its name (21).