Why Probiotics Might be One of the Best Functional Foods

Why are functional foods such a hot commodity? Because they're being hailed as a disease-fighting, health-boosting superpower. No wonder they're growing at a staggering rate - faster, in fact, than other segments of the food market, especially in the most advanced economies.

The story of functional food begins in 1980s Japan, where it all started. Whether in medical journals or everyday conversations, "functional food" is a phrase open to multiple understandings. From cereal to energy bars, products with explicit health claims have flooded the market. Functional foods have had a lot of labels slapped on them over the years. Looking for a definition of functional foods? The Functional Food Center boils it down to this: they're natural or processed foods that contain a potent mix of biologically active compounds. When taken in optimal amounts, these compounds work wonders, providing a tangible health benefit that's backed by biomarkers and cutting-edge research – all to promote peak health and reduced disease risk. By incorporating "bioactive substances" - molecules that boost health through direct physiological impact - this definition takes a bold step forward. The FFC takes on a crucial role in establishing a common language for functional foods, ultimately giving a stamp of approval to the science behind them and boosting their market appeal across the globe.

The umbrella of functional foods is quite wide, covering everything from probiotic yogurts to protein powders. From vitamin-rich treats to foods packed with fiber, flavonoids, and minerals, functional foods are categorized based on the specific ingredients they contain, either naturally or added in. Aside from foods that are low in cholesterol and energy but high in protein, there's another category that stands out: functional probiotic foods and innovative products fortified with postbiotics. Reports abound in scientific literature about how different food components - glucans, polyphenols, probiotics, and prebiotics, to name a few - have been studied for their effects. Affecting the immune response is a very real concern, supported by research findings in multiple studies. Imagine billions of tiny microorganisms calling your digestive tract home - that's essentially what makes up the human microbiome. Living in harmony within our intestines are specific strains of beneficial bacteria, collectively referred to as probiotic bacteria. Live microorganisms that bring a healthy boost to their host are what we call probiotics - provided, of course, they're consumed in sufficient quantities.

Before we can reap the benefits of probiotics, these microscopic wonders must first prove they can survive the treacherous journey through our stomachs and digestive tracts. Probiotics face a tough task: enduring passage through the upper GI tract where potent gastric juices and bile salts pose a constant threat. Yet, for those that persevere, the reward is a fertile ground in which to grow, multiply, and ultimately bring balance to the gut ecosystem.

When a probiotic is capable of directly tuning the body's defense system, it earns the label of immunobiotic. When your immune system is firing on all cylinders, your body is better equipped to tackle the challenges that come its way. Hidden within the twists and turns of our intestines, microbial heroes work overtime to combat invasive bacteria, smother viral invasions, and signal our immune cells to gear up for battle. Imagine your gut as a battlefield, where good bacteria fight off the bad. But when pathogenic microbes get the upper hand, they can lead to dysbiosis, a condition where the good guys are overwhelmed, making the body vulnerable to inflammation and secondary infections. What happens in your gut doesn't stay in your gut - the right balance of microbes is essential for maintaining a healthy gut lining, powering your metabolism, and supercharging your immune system to keep you safe from infection. The role of dysbiosis in spawning diseases has become clear: it's linked to gastrointestinal issues, cardiovascular troubles, obesity, and diabetes, among others.

By casting a wider net in food science research, experts have managed to reel in a surprise catch - a non-viable form of probiotics that's got people talking. Inactive microorganisms, sometimes called postbiotics, paraprobiotics, heat-inactivated probiotics, or even ghost-biotics, are microbial allies that pack a health punch. 

If you break down the term "postbiotic", you'll find its roots in Latin and Greek. The Latin "post" means after, while "bios" comes from the Greek word for life. ISAPP has formally outlined what constitutes a postbiotic: a blend of non-viable microorganisms and their byproducts that yield health benefits to the human host. A key example: 

Beta-hydroxybutyrate (BHB) is a naturally occurring compound classified as a postbiotic, which refers to metabolic byproducts produced through microbial fermentation in the gut. It plays a crucial role in supporting gut health by regulating inflammation and promoting energy production at a cellular level. Research has shown that BHB functions not only as an energy substrate but also as a signaling molecule, influencing gene expression and metabolic pathways. Dr. Jeffrey Volek, a world-renowned researcher in ketogenic science, highlights that "BHB’s ability to serve as both fuel and regulator makes it a powerful compound for metabolic health and inflammation control." This dual functionality positions BHB as a promising nutraceutical for enhancing overall health.

In the world of microorganisms, live bacteria produce and release a variety of soluble compounds. Some of these compounds are enzymes, peptides, and teichoic acids, while others are pieces of bacterial cell walls, like peptidoglycan-derived muropeptides and polysaccharides, that can be released when the bacteria die. The host stands to gain a real physical advantage from this, with bioactivity getting a potent shot in the arm.

The intricate dance of microbes inside us can be influenced through food choices, certain supplements like probiotics and prebiotics, and – when necessary – antibiotics that cull unwanted populations. Research in metagenomic analysis and genome sequencing is painting a vibrant picture of the complex relationships between humans and commensal microbes, highlighting the microbiome's most striking attributes in the process.

Scientists have just caught wind of a promising new idea: tailoring our diets to our unique bacterial armies. What's really taking shape is the concept of a personalized microbiome, built around an individually crafted eating plan. Common foods get a serious boost when they're transformed through technological advancements like lactic acid fermentation, ultimately becoming more appealing to consumers who'd rather not swallow a pill.

Therefore, the objective of this work was to provide a literature review of the possibilities of using probiotics and postbiotics as functional food components affecting the immune response, with the emphasis on the most recently published works.

2. Probiotics and Host’s Immune System

The immune system has a significant impact on the pathogenesis of several diseases. Its main function is to defend the body against various pathogens by recognizing “danger” (damage-associated molecular patterns (DAMPs)) and “stranger” (pathogen-associated molecular patterns (PAMPs)) molecular motifs according to the danger theory [31,32,33].