People generally regard bacteria as harmful and equate them as germs. There are countless ads on TV for bacteria removal. We are taught from a young age to wash our hands after coming home from outside, after going to the bathroom, before touching food, before touching newborn babies…for the purpose of removing bacteria. Disaster flicks such as the 2001 film "Anthrax", as well as various news reports of incidents associated with "meningococcus (meat-eating bacteria)" or "superbugs" really made us flinch at the mere mention of the word "bacteria". Amidst all this negativity and fear towards bacteria, we need to understand that not all of them are bad. While only the bad guys made it onto the news, it is the good guys that keep us healthy and well.
In fact, we cannot live a healthy life without the help of bacteria. There are, on average, 1.1-2.7kgs of bacteria inside of a human body (exact kgs may vary depends on the sources and human subjects). Yes! That's right! Each one of us has kilos of bacteria living inside of us, they live up your nose, in your hair and in your gut, they are pretty much everywhere. Now consider the small size of a single bacterium, a kilo of them means that there are really a lot of bugs. There can be up to 100 trillion bacteria living in your intestine alone, that's almost 10 times the number of human cells present in the entire human body. That's not all, it has been suggested that there are an average of 500 different species of bacteria living in the intestines. These bacteria are what we commonly call intestinal microflora or simply "the good bacteria", which can help us regulate the function and development of the digestive system, maintain proper immune function, reduce/eliminate the number of bad bacteria that we are scared of, and produce useful nutrients and substrates that the body needs. Intestinal microflora are so important to us, they are part of us, so much so, they have been dubbed as the "forgotten organ" of the human body (O'Hara and Shanahan 2006). In this article, we will explore some facts about the good bacteria in our gut, their significance, and what can we do to make sure that they do their jobs properly.
How did the bacteria get in there and what can influence their composition?
The gastrointestinal track of a normal fetus is thought to be sterile. Infants acquire the bacteria from their mother and the surrounding environments during and shortly after birth. It would take up to one month for the intestinal microflora to be well established in an infant after natural birth and up to 6 months if the infant was born by caesarean delivery (Gronlund et al. 1999, Journal of Pediatric Gastroenterology and Nutrition). The composition of the intestinal microflora can be influenced by the diet and living environment of a person.
The use of antibiotics is the biggest culprit for disrupting the natural balance of intestinal microflora. A course antibiotics will not only kill off the bad bacteria that gave you the diseases, it will also destroy good bacteria along with it. Some diseases can also disrupt the balance of the microflora. The use of probiotics can attenuate the imbalance and potentially return the intestinal microflora to normal levels.
What are probiotics and what are their benefits?
Probiotics are defined as non-pathogenic living microorganisms that contribute to the intestinal microbial balance when consumed in adequate amounts (Modified from Parker 1974). The most common natural probiotics are fermented foods such as yogurt, cheese and sauerkraut. In comparison, probiotic supplements are more concentrated and defined, but have a less variety of microorganisms compared to natural foods. Even though there are hundreds of species of beneficial microorganisms naturally living in the gut, years of research have helped to identify the most potent ones of the lot. Hence most probiotic supplements today contain a large number of the few bacterial species and strains. These bacteria have a high survival rate to ensure that there will be enough of them that can pass through the acidic environment of the stomach to reach the intestines after ingestion and stay alive. The most commonly used bacterial species in probiotic supplements are various strains of lactobacilli and bifidobacteria.
What are the positive effects of probiotics?
The positive effects of probiotics have been widely researched over the years in both animals and humans. The use of probiotics in humans is thought to have the following benefits (Toole and Cooney 2008, Interdisciplinary Perspectives on Infectious Diseases):
- Improve immune function by enhance T-cell (a type of immune cell of the adaptive immune system) numbers and activation levels.
- Reduce inflammation by promoting the production of anti-inflammatory cytokines.
- Reduce symptoms caused by Irritable Bowel Syndrome (IBS).
- Reduce number of pathogens in the gut by directly inhibiting their growth.
- Reduce the risk of certain cancers by detoxifying carcinogenic (cancer causing) metabolites.
- Enhance the value of nutrients by producing vitamins and co-factors.
- Improve the function of gut barrier by promoting its integrity.
- Reduce allergy and food intolerance symptoms by suppression of hypersensitivity and catabolize dietary ingredients.
- Reduce the risk of cardiovascular diseases by de-conjugate bile salts to reduce cholesterol levels and produce anti-hypertensive peptides.
Effects of probiotics on metabolic disorders, diabetes and obesity
Recent studies have linked intestinal microflora imbalance to metabolic disorders, type 2 diabetes and obesity. It has been found that obese animal and human subjects have altered intestinal microflora composition in comparison to their lean counterparts (Sanz et, al. 2010, The Proceedings of the Nutrition Society). It is thought that intestinal microflora can provide additional metabolic functions and regulate the host's gene expression to improve the body's ability to extract and store energy from diet, and thus influence body weight. The supplementation of probiotics and its effect on body weight composition has been investigated. The supplementation of bifidobacterial in rats yielded reduced body weight and fat accumulation as well as their lipid profile and glucose-insulin homeostasis compared to the control rats. On the other hand, the studies conducted using human subjects are inconclusive and yielded mixed results (Shen et al. 2012, Molecular Aspects of Medicine). The duration of the studies were too short to determine the effect on body weight, and the parameters of many studies were usually not well defined (Sanz et, al. 2012, Pharmacological Research). Thus, better designed studies and further in-depth analysis are required to determine the effects of various strains of microbes on obesity and other metabolic disorders.
Probiotics and sports
Heavy and prolonged exercise, such as marathon running can increase the risk of upper respiratory track infections, and strenuous exercise can cause gastrointestinal symptoms (Kekkonen et al. 2007, International Journal of Sport Nutrition and Exercise Metabolism). The administration of probiotics (lactobacillus) has been found to reduce the length of time an athlete experience respiratory symptoms (Cox et al. 2010, British Journal of Sports Medicine) and shorten the duration of gastrointestinal symptoms (Kekkonen et al. 2007, International Journal of Sport Nutrition and Exercise Metabolism) post exercise. However, the supplementation of probiotics did not seem to improve the performance of the athletes in the above studies.
Risks of taking probiotics
There are always two sides of every story and the use of probiotics is no exception. The following points need to be considered before choosing and taking probiotics to ensure maximum benefits with minimum side effects.
- Probiotics are living microorganisms thus may cause infections in immunocompromised people.
- Probiotic supplements may cause allergic or food intolerance reactions. These reactions may be caused by the ingredients contained in the probiotics to keep the microorganisms alive. Therefore, it is important to choose the right product that does not contain undesirable ingredients (ie. Choose dairy free probiotics if you are allergic to dairy products).
- Even though it is rare, but probiotics can sometimes interact with other drugs such as sulfasalazine.
- Taking probiotics can sometimes cause digestive discomfort, such as bloating, diarrhea, constipation and flatulence. The discomfort usually goes away within a week after continued ingestion. However, sometimes the discomfort may be caused by a particular type of probiotics and when such incident occurs, changing to a different brand of probiotics may eliminate the problems.
Maintaining a properly balanced intestinal microflora is essential for living a healthy, feel-good life. Of course, not disturbing the balance of the microflora in the first place would be ideal. However, such feat is difficult to achieve for most people, for instance, most of us have taken antibiotics at some point in our lives. Taking appropriate probiotics supplements can provide the means of replenish the beneficial microflora population in the gastrointestinal track and hence to help the body to regain its balance that was once disrupted.