There is a rising interest in an area of nutrition that is commonly referred to as 'gut health', or digestive health. Many people are discovering that their bodies are filled with bacteria, some helpful and a few which can cause illness [1]. The helpful bacteria are grouped into a generalized category called 'probiotics'. Bacteria are microorganisms, they are a life form of their own kind which live wherever there is an environment which can sustain them. From a nutritional perspective, helpful bacteria that we consume to achieve health benefits are probiotics [2]. Many health benefits have been associated with maintaining the correct digestive bacteria [3][4] including:

Weight Loss

Better Digestion

Improved Immune Function

Skin Health

There is Even Evidence that Probiotics Reduce the Risk of Some Diseases

Dietary Sources of Probiotics

We can consume probiotics without even knowing it. Many fermented foods, such as yogurt, sauerkraut and kefir, are abundant in bacteria that help break down food and process the nutrients in a way that make them available to our bodies to use. Probiotics are also sold as dietary supplements. As the awareness of the importance of healthy gut flora becomes more widespread, more supplement manufacturers are isolating the bacteria which are thought to be beneficial. Probiotic supplements have species of cultivated bacteria living inside, ready to go to work. Supplement labels will list the genus, species and specific strain of the bacteria which are sold [5]. Some of the common types of probiotics are Lactobacillus, Bifidobacteria, Escherichia, and Bacillus strains, just to name a few. They all behave differently, and selecting the right probiotic is crucial. Many probiotics address the consumer's concern about which strain to choose by combining many strains into a blend. Probiotic blends provide a broad spectrum of beneficial bacteria.

The Impact Probiotics Have on Digestion

There is a complex ecosystem living inside you, sometimes referred to as gut flora or microbiome [6][7]. The gut flora is a community made of various archea, helminths, viruses and fungi in addition to bacteria [8]. The overwhelming majority of microorganisms found in the digestive tract is bacteria, comprising between 300 to 500 species. Most of the gut flora lives in the large intestine [9]. Metabolic functions performed in the gut microbiome mimic the activities of an organ and have some scientists naming the gut microbiome as the 'forgotten organ' [10]. Many important processes happen during digestion, including the production of vitamins, like vitamin K and B vitamins [11]. Fibers are also processed into short-chain fats, which feed the walls of the gut and carry out many metabolic actions [12][13]. Short-chain fats strengthen the gut wall, but also stimulate the immune system. This may help prevent undesirable compounds from entering the body and causing an immune response [14][15].

The researchers and scientists who study the effects of probiotics in clinical settings often disagree about which strains are beneficial and what the true health benefits are [16].

Many diseases are linked to an unbalanced gut microbiome, according to studies [17][18]. The flora are very sensitive to diet, and an unbalanced gut flora is thought to be a contributing factor to diseases [19][20][21][22]

Diseases Linked to Unbalanced Digestive Flora

Type 2 Diabetes

Obesity

Heart Disease

Metabolic Syndrome

Depression

Colorectal Cancers

Alzheimers

Probiotics can help maintain the balance of the microbiome or help correct an imbalance [23). However, as the gut flora are highly sensitive, caution must be taken to avoid creating an imbalance. It is important to know that whatever supplements you take are helping you, follow advice given by your doctor and always consult your doctor before trying new supplements.

Scientific Interest in Probiotic Research

Probiotics are a widely researched topic in the field of digestive health [24]. There is evidence to suggest that probiotic supplements may help with the symptoms of diarrhea associated with the use of antibiotics, especially long-term antibiotic use [25]. Antibiotics tend to kill bacteria, including many of the helpful kind which facilitate healthy metabolic functions. This sometimes causes an imbalance which allows harmful bacteria to take over and thrive. Irritable bowel syndrome is another ailment that many people suffer from, and probiotics may be beneficial to those that are afflicted. A research review published that the results from seven studies suggested improvement of IBS after supplementing with a probiotic, however four studies did not show improvement [26].

The research seemed to suggest that irritable bowel symptoms were more effectively alleviated by a probiotic blend than a single strain probiotic, especially when the length of time the supplements were taken for more than 8 weeks [27]. More data is needed before probiotics can be used as a treatment for IBS, however. Questions that still haven't been answered are [28]:

Which probiotics/ probiotic blends are most effective?

Which symptoms of IBS are improved by probiotics?

Are different probiotics required to improve different varieties of IBS?

What is the best dosage?

How long should probiotics be taken?



Researchers agree that while the preliminary findings show some promise, much more research in larger trials needs to occur before healthcare professionals can prescribe probiotics as a possible treatment for IBS or any other bowel diseases caused by inflammation, such as Crohn's or ulcerative colitis [29].

Are Probiotic Supplements Safe?

The research surrounding probiotics is very exciting to learn about, and many studies show promising clues that probiotics may be useful for a wide range of health applications. However, there are some researchers who caution about potential negative side effects. There simply isn't enough available research to claim that taking probiotics doesn't carry the risk of side effects, or what the potential side effects are. Some researchers warn against taking probiotics and there have been calls for the regulation of probiotic supplements [30][31].

Weight Loss

A common reason some choose to take probiotic supplements is weight loss. Some research shows that people who suffer from obesity have different digestive bacteria than those who are not obese [32]. While some probiotic strains appear to aid weight loss [33], more research is needed to determine how this data applies to the consumer.

Summary of Findings

Any bacteria that are beneficial to our bodies' digestive process may be considered a 'probiotic'. There are studies which show some strains of probiotics may be effective in helping certain digestive issues, weight loss, and improved immune function. There is quite a bit more research that needs to be done before probiotics can be declared a 'cure' for anything, and caution should always be applied before taking any supplement. Always ask your doctor what is right for you based on your current health conditions, always seek medical guidance prior to consuming any supplements.

1) https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4425030/

2) https://doi.org/10.1038/nrgastro.2014.66

3) https://www.mdpi.com/2072-6643/11/7/1613/htm#B70-nutrients-11-01613

4) http://www.tlsr.usm.my/tlsr27022016/27022016_06.pdf

5) https://www.worldgastroenterology.org/UserFiles/file/guidelines/probiotics-and-prebiotics-english-2017.pdf

6) https://doi.org/10.1136/bmj.k2179

7) https://www.sciencedirect.com/topics/medicine-and-dentistry/gut-microbiome

8) https://dx.doi.org/10.3390%2Fmicroorganisms8040483

9) https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3983973/

10) https://jbiomedsci.biomedcentral.com/articles/10.1186/s12929-019-0554-5

11) https://dx.doi.org/10.1007%2Fs00394-017-1445-8

12) https://www.ncbi.nlm.nih.gov/pubmed/25273884

13) https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4275385/

14) https://www.ncbi.nlm.nih.gov/pubmed/25481240

15) https://www.ncbi.nlm.nih.gov/pubmed/24891972

16) https://www.tandfonline.com/doi/full/10.1080/19490976.2017.1345414

17) https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4566439/

18) https://www.mdpi.com/1422-0067/16/4/7493/htm

19) https://dx.doi.org/10.3389/fmicb.2018.01835

20) https://www.clinicsandpractice.org/index.php/cp/article/view/987/834

21) https://www.ncbi.nlm.nih.gov/pubmed/2449552722

22) https://www.frontiersin.org/articles/10.3389/fcimb.2020.00104/full

23) https://dx.doi.org/10.1016%2Fj.tifs.2020.06.010

24) https://dx.doi.org/10.1042%2FBCJ20160510

25) https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5745464/

26) https://www.mdpi.com/2072-6643/11/9/2048/htm

27) https://badgut.org/information-centre/a-z-digestive-topics/probiotics-for-irritable-bowel-syndrome/

28) https://doi.org/10.1016/j.jinf.2017.12.013

29) https://www.ncbi.nlm.nih.gov/pubmed/25525379

30) https://dx.doi.org/10.4155%2Ffsoa-2019-0004

31) https://dx.doi.org/10.3390%2Fmicroorganisms7040104

32) https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5082693/

33) https://www.mdpi.com/1422-0067/16/4/7493/htm