What Are Synbiotics?

There has been a boom in research into our gut microbiome (a term that refers to all the trillions of microorganisms that live in our digestive tract) in recent years.

Largely due to advances in technology and reductions in certain costs, but also spurred on by the incredible information being uncovered from this research. (Source)

This surge of knowledge around the importance of gut health has filtered through to the general population, making people more clued into their digestive health than ever before.

So why is maintaining a healthy gut so important? While researchers are still learning how exactly our gut impacts our health, they do know an unhealthy gut not only affects our digestion but can also negatively affect other body systems, including our brain, skin, immune system, and our overall health. (Source)

This is because the bacteria that live in our gut are in constant communication with other parts of our body through what are called axes. For example the gut-brain axis, the gut-skin axis, and the heart-gut axis.

These interactions are complex and work in both directions. Just as the health of our brain or immune system can influence our gut health, our gut microbiome can have a direct effect on the health of these body systems too. (Source)

So by looking after our gut, we’re looking after our entire body.

In this article, we’ll look at synbiotics, a term used to describe a mixture of probiotics and prebiotics and their effect on gut health. Read on and find out what are synbiotics.

The Role Of Prebiotics And Probiotics

Prebiotics

Prebiotics are specific types of plant fibers that are not digested by our gut but feed the ‘friendly’ bacteria living there. (Source)

Within the microbiome, there are types of microorganisms that are beneficial to our health and other types of bacteria that are harmful to our health.

The beneficial bacteria keep our gut working optimally by helping to digest our food properly, absorb nutrients and regulate inflammation.

If we have more harmful bacteria present in our digestive tract than beneficial bacteria this results in an imbalance called dysbiosis. Dysbiosis can lead to digestive issues such as bloating, constipation, coeliac disease, and inflammatory bowel diseases (IBD), and has also been linked to non-gut related issues including diabetes, arthritis, obesity, colorectal cancer, depression, and cardiovascular disease. (Source)(Source)

This is why it’s important to encourage the growth of beneficial bacteria, which is what prebiotics do.

Prebiotics have been shown to exhibit several benefits including:

• Enhancing the bioavailability and uptake of minerals (Source)
• Reducing the prevalence and duration of diarrhea (Source)
• Relief from inflammation and other symptoms associated with intestinal bowel disorder (Source)
• Protective effects to prevent colon cancer (Source)
• Lowering of some risk factors of cardiovascular disease (Source)
• Promoting satiety and weight loss (Source)

Prebiotics can be found naturally in many fruits, vegetables, and whole grains, such as green veg, legumes, bananas, berries, onions, garlic, and soybeans.

Some products such as bread, cereal, and yogurt, have prebiotics added to them. If you’re looking for such products, they’ll likely say they’re fortified with galactooligosaccharides, fructooligosaccharides, oligofructose, chicory fiber, or inulin, which are all types of prebiotics.

Prebiotics are also available in dietary supplement form.

Probiotics

Probiotics are beneficial bacteria that naturally live in our gut but can also be found in certain foods such as probiotic yogurt and kefir.

Probiotics are what feed on prebiotics. 

We naturally have probiotics living in our digestive system but consuming probiotics is a great way to increase further the number of these beneficial bacteria in our gut. This can lead to a decrease in the number of harmful bacteria, leading to improvements in digestion and overall health too. (Source)

Much research has been done on probiotics, but there is still much to be learned about their benefits to our health.

Research so far shows that probiotics may help to:

• Restore a healthy balance of bacteria in the gut (Source)
• Improve digestion (Source)
• Regulate bowel movements (Source)
• Improve energy levels and immune function (Source)
• Improve mood (Source)
• Contribute to vaginal health (Source)

Probiotics are naturally found in fermented foods such as probiotic yogurt, kefir, kombucha, sauerkraut, pickles, miso, tempeh, kimchi, and some cheeses, and are also available in supplement form.

Synergy Between Prebiotics And Probiotics

Prebiotics and probiotics need each other and function synergistically to support the gut microbiome. They work hand in hand.

Getting plenty of probiotics replenishes the gut with beneficial bacteria and because prebiotics are the food these bacteria feed on, they’re important to sustain these good bacteria. 

Understanding Synbiotics

Origin Of Synbiotics

The term synbiotics was first introduced in 1995 by professors Glenn Gibson and Marcel Roberfroid. The name “synbiotics” was created to refer to a mix of probiotics and prebiotics that work together in a targeted way to benefit the “good” bacteria in a person’s gut. (Source)

The understanding of synbiotics progressed over the decades and in 2019 synbiotics were split into two types – complementary synbiotics and synergistic synbiotics.

A complementary synbiotic is a mixture of a probiotic and a prebiotic where the probiotic strain is selected based on the benefits that it provides to the patient and the prebiotic helps promote the growth and function of the beneficial bacteria in the gut in general, providing a health benefit.

A synergistic synbiotic contains a prebiotic that is designed specifically to be used by the particular probiotics it is with. In this case, the probiotic is chosen based on its ability to provide a health benefit, and the prebiotic is selected to mainly support the growth or activity of the specific probiotic selected, rather than probiotic bacteria in general. (Source)

Most commercial synbiotics as well as those used in clinical trials have been of the complementary type as thus far relatively few synbiotic studies have tested for synergism.

Mechanism Of Action

A synbiotic product works by providing beneficial bacteria to the gut as well as the food they survive on. In doing this, synbiotics support the growth of this bacteria and improve its survival, helping to restore balance in the gut microbiome.

Synbiotics were developed to overcome possible survival difficulties for probiotics. Synbiotics have been seen to improve the survival of probiotic bacteria as they pass through the stomach and upper intestinal tract and stimulate the growth of this “good” bacteria in the gut. (Source)

Benefits Of Synbiotics

Improvement Of Gut Health

As mentioned, dysbiosis, an imbalance in gut bacteria where there are more harmful bacteria in the gut than beneficial, is detrimental to gut health.

To maintain a healthy gut, we must keep strong levels of a variety of beneficial bacteria in the gut. (Source)

Supplementation with synbiotics has been seen to increase the amount of gut bacteria associated with positive health effects, while also appearing to increase the gut microbiota richness. In doing this, synbiotics contribute to the maintenance of the balance of the intestinal microbiome, improving overall gut health. (Source)

Enhanced Immune Function

Synbiotics have been shown to enhance certain aspects of immune function, likely due to the role of probiotics in improving immune system responses. (Source)

In one study on chickens, supplementation with synbiotics for 6 weeks resulted in a significant reduction in the levels of C-reactive protein, a marker of inflammation, and also increased levels of glutathione levels, a powerful antioxidant. (Source)

Other animal studies in rats also found that synbiotic supplementation positively affected inflammation levels. (Source)(Source)

Although more research in humans is needed, synbiotics appear to have a beneficial effect on inflammation and immune response.

Better Nutrient Absorption

Research suggests that synbiotics also improve the absorption of calcium, magnesium, and phosphorus in the gut. (Source)

This is possibly due to the prebiotics. Several studies in animals and humans have shown the positive effects of prebiotics on mineral absorption and metabolism. (Source)

The same effect has been seen in studies with synbiotics. A study in rats found that infant formula supplemented with synbiotics significantly increased the bioavailability of calcium, magnesium, and phosphorus. (Source)

An overall improvement in gut health from synbiotic supplementation may play a role in this, but it could also be due to the greater production of compounds called short-chain fatty acids (SCFAs), which have been seen to enhance the absorption of some nutrients, by the gut bacteria due to the increase in food.

Furthermore, as bacteria ferment the food in our gut, some of the products that are created can promote the growth of the gut cells that absorb nutrients. (Source)

Management Of Certain Health Conditions

Inflammatory Bowel Disorder

Several studies on both acute and chronic intestinal inflammation suggest that probiotics, prebiotics, and synbiotics may be helpful in the management of inflammatory bowel disorders by reducing inflammation in the gut. (Source)

Hypercholesterolemia

Synbiotics have also shown promise in controlling cholesterol, with a number of studies finding synbiotics to demonstrate beneficial effects on cholesterol levels. (Source)

For example, one study reported that the regular intake of synbiotic yogurts reduces the risk of cardiovascular disease among hypercholesterolemic patients. (Source)

Another recent study found that 12 weeks of synbiotics supplementation among women with polycystic ovary syndrome resulted in beneficial effects on cholesterol levels. (Source)

Colorectal Cancer

While research is limited, there is evidence to suggest that probiotics, prebiotics, and synbiotics exert anti-cancer effects. (Source)

For example, one study in patients with colon cancer found that 12-week supplementation with synbiotics resulted in significant bacterial changes and concluded that several colorectal cancer biomarkers can be improved by synbiotic intervention. (Source)

Sources Of Synbiotics

Naturally Occurring Synbiotic Foods

There aren’t many naturally-occurring synbiotic foods. For a food to be synbiotic it would have to contain both probiotics and prebiotics, which is rare.

Fermented foods like sauerkraut and kimchi can be synbiotic. They often include onions and garlic (which are good sources of prebiotics), and the fermentation process enhances the number of probiotics they contain. 

Synbiotic Supplements

Synbiotics are more commonly found in supplement forms or as functional foods.

Synbiotic supplements may not include the word “symbiotic” on the label. Any supplement containing both a probiotic and a prebiotic is a synbiotic, and many probiotic supplements have prebiotics included in them. You may even be taking a synbiotic and not realize it!

Functional Synbiotic Foods

Functional foods are foods that offer health benefits beyond their nutritional value.

This can be foods packed with antioxidants like fruits and veggies, or foods fortified with vitamins, minerals, probiotics, and fiber.

If food technologists add prebiotics to a probiotic food, probiotics to a prebiotic food, or probiotics and prebiotics to any food – that food becomes synbiotic.

For example, because yogurts and kefir are natural probiotics, some manufacturers are adding prebiotics to make the product a symbiotic.

However, if you’re looking out for them, it’s unlikely they’ll say “symbiotic” on the product. Check the label for ingredients such as inulin or chicory root fiber. These are both prebiotics.

Choosing Synbiotic Products

If you’re interested in trying out synbiotic products, whether in food or supplement form, it is important to choose one with a probiotic strain suited to you. Different probiotic products contain different strains of probiotic bacteria and each strain works to relieve specific symptoms.

Make sure to choose a product that contains the combination of strains best suited for your particular health concern. Consult your healthcare practitioner for more advice on the best product for your specific concern if you’re unsure.

As well as this, some people find they get on better with some types of prebiotics more than others. Keep an eye on the type of prebiotics in your product and if you find you’re having issues, try out a product with a different type of prebiotic instead. 

Precautions And Possible Side Effects

Anyone who is sensitive to prebiotics or probiotics should avoid synbiotics.

Because prebiotics are fermented in the gut they can cause some digestive side effects when consumed in high amounts. Some people may complain of increased bloating, gas, abdominal pain, and cramping after taking prebiotics. This is due to excessive bacterial fermentation in the gut and subsequent gas production. Those with IBS may be particularly susceptible to these side effects. (Source)

Probiotics may also contribute to negative side effects, such as diarrhea or abdominal pain. These are particularly common when someone first starts supplementing with probiotics, as their gut adjusts. For this reason, it’s best to start with a low dose of synbiotics and then increase gradually if well tolerated.

While these effects often subside after a short while, some people may always struggle to digest synbiotics.

It is best to consult with a healthcare professional before taking probiotics, prebiotics, or synbiotics so that they can advise on product and dosage, as well as monitor any symptoms.

It is also important to increase your water intake when consuming more prebiotic foods. This is because prebiotic foods are typically high in fiber, which absorbs water in the colon.

This can slow down digestion and may also cause dehydration and constipation. Drinking more water can help prevent these adverse side effects and keep things running smoothly within the digestive tract.

Final Thoughts

With our gut health having such a profound impact on so many of our body systems, taking care of our gut is paramount to maintaining our overall health.

What we eat plays a huge role in this. As well as eating a wide variety of plants and fiber, prebiotic foods have been shown to benefit gut health by being a particularly popular foodstuff amongst the beneficial bacteria in our gut.

Synbiotics have also been seen to provide benefits by adding more beneficial bacteria to the gut due to their probiotic content and also sustaining it with their prebiotic content.

There are some limitations when it comes to synbiotics, however. For a synbiotic to be effective, its probiotics must reach the gut alive, which can be challenging.

As is the case with many probiotic products, too, in many cases, it is hard to know whether the probiotics successfully make it to the gut intact to work their magic.

Choosing a high-quality product with evidence of efficacy can help to allay these concerns.

Also, because symbiotic products are considered dietary supplements, they’re not tightly regulated by the FDA. So it is important to choose a high-quality supplement that is tested for safety and effectiveness.

Always consult with your doctor before trying a new supplement.

Lucy Brennan, ANur, BSc

Lucy Brennan is a registered associate nutritionist (ANutr) and freelance writer specializing in health, nutrition and wellness content.  She holds a BSc. (First Class Hons) in Public Health Nutrition and has over 4 years’ experience working in health communication, which is where her passion lies.

She has worked in roles with The Irish Food Board and FleishmanHillard PR, on their healthcare team, working with national and international health companies. Using this experience, Lucy now writes content in a freelance capacity. Lucy is dedicated to providing evidence-based content that is both engaging and accessible and inspires readers to make informed choices regarding their health.