Nutrition Meets Food Science


“The road to health is paved with good intestines!” – Sherry A. Rogers

When we think of bacteria the first thing that comes into our mind is harmful bacteria and germs but there are good bacteria’s too and probiotics is one such category. And it seems like probiotics are all the rage right now – they’re taking over health food stores, social media and gaining a lot of attention among consumers. But what exactly are probiotics, and what can they do for your health?

The concept of probiotics evolved back during the 19th century. In 1907, a Russian scientist named “Elie Metchnikoff” proposed that the gut flora could be modified and harmful microbes can be replaced with beneficial ones. The term probiotics is derived from the Greek meaning “for life”. The benefits of probiotics have come to light in recent years.

Probiotics are “live microorganism administered in adequate amounts which confer a beneficial health effects on the host” (FAO/WHO, 2002).

In simple terms Probiotics are the ‘good’ bacteria that live in your digestive system. They help your body break down and absorb the nutrients in your food, assist in regulating immune system, and reducing the development and spread of harmful bacteria.


Probiotics and prebiotics might sound similar but they are entirely different. However, both of them are reliant on each other. Probiotics when feed with prebiotic foods, they get the fuel needed to colonize the gut and improve digestive health.

Prebiotics are non-digestible ingredients like galactooligosaccharides, fructooligosaccharides, oligofructose, inulin in foods that are used to spur the growth of probiotic bacteria in the body by providing a suitable environment in which the probiotics themselves can flourish and improve digestive health. Prebiotics can be found in foods such as tomatoes, artichokes, bananas, asparagus, berries, garlic, onions, chicory, legumes, oats, flax, barley, and wheat, etc.

Probiotics and prebiotics, or as they are collectively known ‘synbiotics’ are the most important and frequently used functional foods. Functional foods can offer potential health benefits in addition to the widely accepted nutritional effects.


Hundreds of different bacterial species are the natural and predominant constituents of intestinal microbiota. Among the numerous intestinal microbes, those anticipated to exhibit potential health benefits to the host through modulation of the intestinal microbiota are commonly selected as probiotics.

Different strains of bacteria have different health benefits, and a strain can be classified as probiotic only if it has scientifically proven health benefits. Many foods contain live bacteria associated with health benefits, such as sauerkraut, yogurt, and kimchi. However, unless those bacteria are shown to have health benefits and are present in a large enough quantity to have that beneficial effect, they cannot be called a probiotic. As a result, although many probiotic bacteria are found in food, they are not in sufficient quantities to offer the same health benefit as a probiotic supplement.

The requirement for a microbe to be considered a probiotic (Binda et al.,2020) :

  1. Micro-organism must be alive and administered and should be documented to have a health benefit and must be administered at levels shown to confirm the benefits.
  2. To be effective, probiotics must survive intestinal transit and must also be able to lodge in intestine.
  3. They must able to tolerate low pH and high concentrations of both conjugated and deconjugated bile acids.
  4. Probiotics products must be safe and effective, and they should retain their effectiveness and potency all throughout end product’s shelf life.
  5. Should be resistant to harmful bacteria.
  6. It should be non-pathogenic and stable, with no toxins released by the bacterium.

Specific Strains with Probiotic Properties

Lactobacilli species are commonly selected as probiotics since they express many crucial properties such as: high tolerance to acid and bile, capability to adhere to intestinal surfaces, withstanding low pH, gastric juice, inhibiting potentially pathogenic species (antimicrobial activity), resisting antibiotics, producing exopolysaccharides and removing cholesterol (Tulumoglu et al.,2013) .It has been seen that certain strains of Lactobacilli are effective in preventing antibiotic-associated diarrhoea (Johnston et al.,2011).Lactobacillus rhamnosus CRL1505 has even been effective in reducing viral-associated pulmonary damage through controlling immune-coagulative responses and clearing respiratory viruses( Zelaya et al., 2014).

Strains of the Genus Bifidobacterium are also frequently used as probiotic bacteria because of their diverse resistance mechanisms to bile salts, which is important because probiotic bacteria’s beneficial effects must be generated in the presence of this biological fluid. Several strains of bifidobacteria are considered as important probiotics including: Bifidobacterium infantis, B. adolescentis, B. animalis subsp animalis, B. animalis subsp lactis, B. bifidum, B. longum, B. breve. Bifidobacterium species together with other probiotics have been proven to treat constipation, travellers’ diarrhoea (McFarland.,2007). antibiotic-associated diarrhoea, maintaining remission of disease activity of gut inflammation and moderate ulcerative colitis (Dylag et al.,2014).

Escherichia coli is a very common inhabitant of the lower intestine and even a probiotic strain is known: Escherichia coli Nissle 1917 (EcN). This probiotic strain has been effective in treating constipation and inflammatory bowel disease (Behnsen et al., 2013).This strain may also help with gastrointestinal disorders such as ulcerative colitis and Crohn’s disease.

The genus Bacillus includes Gram positive spore-forming aerobic or facultative aerobic members with claimed probiotic properties including: B.subtilis, B. coagulans, B. subtilis, B. cereus.Bacillus coagulanstogether with other microorganisms has proven to be most successful in preventing or treating antibiotic-associated diarrhoea (Hempe et al.,2012).

Genus Lactococcus are also sometimes recommended as probiotics as they are important in preventing growth of spoilage bacteria in milk products due to acidification Certain strains of Lactococcus lactis subsp. lactis have probiotic properties such as adhesion to vaginal epithelial cells and nisin production (Lactococcus lactis subsp. lactis CV56) (Gao et al.,2011) and are also used to treat antibiotic-associated diarrhoea in combination with other probiotics (Johnston et al.,2011).


You might be wondering what happens in your body when you use a probiotic, and how they actually generate a health benefit. Probiotics are made up of good bacteria that help to keep the body healthy and working efficiently. These beneficial bacteria can fight off bad bacteria when you have too much of it, helping to power up the immune system to get you well again.

When ingested, the bacteria in probiotics compete against potentially pathogenic microbes in the gastrointestinal tract to try and inhibit their harmful effects. They can do this by producing anti-microbial substances that can kill off opportunistic pathogens and by binding onto viruses themselves. That’s why having a wide and varied number of ‘good bugs’ or bacteria in the gut has also been shown to dampen allergies and sensitivities, support the immune system, enhance nutrient absorption and much more.

Probiotics can improve health through several mechanisms:

  • Interact with other microorganisms in our microbiome.
  • Stimulate growth of beneficial bacteria in our microbiome.
  • Inhibit growth of harmful bacteria in our microbiome.
  • Interact directly with our body’s organs, such as the intestine.
  • Produce compounds that reduce inflammation or alleviate leaky gut.
  • Modulate our immune system.


Probiotics benefit your health in a variety of ways, which vary depending on the strain. There is increasing evidence in favour of the claims of beneficial effects attributed by probiotics. According to research, probiotics may provide following potential benefits:

Probiotics and Gut Health

The gut microbiota is the centre of much current research. Researchers are suggesting that an imbalance in the gut microbiota could lead to several health issues including immune dysfunction, infection, obesity, and GI problems.

Using a probiotic to restore balance has been shown to alleviate symptom persistence in irritable bowel syndrome (IBS) by 21% using both single-strain and multiple-strain supplements, with the mixtures being most effective (McKenzie et al.,2016). A healthy gut with plenty of good bacteria has also been shown to improve the immune system, combat inflammation, and potentially reduce bad cholesterol (total and LDL cholesterol) (Cho et al.,2015).

Probiotics and Diarrhoea:

It is estimated that every 15 seconds, a child dies from diarrheal disease somewhere in the world. Many types of diarrheal disease with many causes disrupt intestinal function. The ability of probiotics to decrease the incidence of duration of certain diarrheal illness is perhaps the most well-established of the health effects of probiotics (Maria et al.,2013).

Probiotics and Elevated Blood Cholesterol

Cholesterol is essential for many functions in the human body. It acts as a precursor to certain hormones and vitamins, and is a component of cell membranes and nerve cells.
However, elevated levels of total blood cholesterol and other blood lipids are considered risk factors for developing coronary heart disease.

Probiotic cultures have been evaluated for their effect on serum cholesterol levels. Clinical studies show the effect of lowering cholesterol levels in humans, have not been conclusive (Nguyen et al.,2007).

Probiotics and Cancer

Lactobacillus acidophilus is known to prolong the induction of colon tumors. It was demonstrated that feeding milk and colostrum fermented with L. acidophilus resulted in 16–41 % reduction in Tumor proliferation (Andrews and Tan 2012). It has been hypothesized that probiotic cultures may decrease the exposure to chemical carcinogens by detoxifying ingested carcinogens and nitrosamines, altering the environment of the intestine and thereby decreasing population of bacteria that may generate carcinogenic compounds. (Lee et al.,2012).

Lactose Intolerance

The inability of adults to digest lactose or milk sugar is prevalent worldwide. Consumption of lactose by those lacking adequate levels of lactase produced in the small intestine can result in symptom of diarrhoea, bloating abdominal pain and flatulence. These symptoms are due to undigested lactose reaching the large intestine and being permitted by the colonic microbes.

The possible pharmacological interventions for lactose intolerance were treatment with commercially available lactase tablets or probiotics such as Lactobacillus bulgaricus and Streptococcus thermophiles. It has been also observed that consumption of milk containing Bifidobacterium longum and L. acidophilus cause significantly less hydrogen production and flatulence. The combination of Lactobacillus caseishirota and Bifidobacterium breve Yakult has shown better effect and improved the symptoms of lactose intolerance significantly (Vonk et al.,2012).


The range of food products containing probiotic strains is wide and still growing. The main products existing in the market are dairy-based ones including fermented milks, cheese, ice cream, buttermilk, milk powder, and yogurts, etc.

At present probiotics are almost exclusively consumed as fermented dairy products such as yogurt or freeze- dried cultures, but in future they may be found in fermented vegetables and meats.

Foods that contain probiotics include:

  • Aged cheeses
  • Kefir
  • Yogurt
  • Cultured buttermilk, cottage cheese, and sour cream
  • Fresh pickles
  • Kimchi
  • Kombucha
  • Water kefir and other “probiotic” beverages
  • Sauerkraut
  • Tempeh
  • Raw vinegar, including apple cider vinegar

Probiotic supplements contain live bacteria and have a limited shelf life due to bacteria dying over time. Because of this, probiotic supplements provide the number of bacteria they contain at the date of manufacture and the amount they will contain by their expiry date. The expiry date indicates the point at which there are no longer enough living bacteria to gain any health benefit from consuming the probiotic. Live bacteria cultures in probiotics are usually referred to on the label as colony-forming units (CFUs).

While buying any probiotic product one must look for is the full probiotic name, which includes the genus, species, and then the strain. Many products containing probiotics list only the genus and species on the package, such as “bifidobacterium lactis.” The dosage of probiotic foods and supplements is determined solely by the number of live organisms present in the product. Clinical trials with 107 to 1011viable bacteria per day yielded positive results (Khalighi et al.,2016). It was observed that 100 times fewer viable bacteria are required in a dairy medium than in a freeze-dried supplement to attain similar numbers of live bacteria in the lower bowel. Dairy has seemed to be an ideal transport medium for bacteria, enhancing their survival through the upper GI tract (Kailasapathy et al.,2000)

More to Consider

Though probiotics exhibit numerous health benefits one should always consider the following factors before inculcating it into our diet:

  • World Gastroenterology Organisation recommends that probiotic supplement users check the labels of probiotic supplements for recommended storage conditions; for example, some require refrigeration, whereas others can be stored at room temperature.
  • One should not use probiotics as a reason to postpone seeing your health care provider about any health problem.
  • 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.

Therefore, while the overwhelming existing evidence suggests that probiotics are safe, complete consideration of risk-benefit ratio before prescribing is recommended.

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Nitushri Raut

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