Like an oxpecker is to a rhino, so too is our gut bacteria to our health and wellbeing. You’ve no doubt heard that our human gut bacteria is the next big thing in nutrition science. Research is beginning to show that our gut bacteria and gut environment has a massive influence on not only our digestive health, but also is the severity and prevention of chronic diseases including obesity, cardiovascular disease, diabetes and even cancer(1, 2).
How does gut bacteria influence obesity?
It’s a tough question that science is still not 100% sure of. However, research in mice is indicating that the type of gut bacteria that you have could be influencing your body composition. The human gut contains between 107 and 1012 cell/g of different bacterial species; Firmicutes and Bacteroidetes making up most of these(1, 3, 4). The ratio between these Fimicutes and Bacteroidetes has been linked to adiposity, potentially influencing obesity and other related diseases. It has been found that the genetically obese mice, when compared with lean mice, have less than 50% fewer Bacteroidetes and a greater number of Firmicutes(5). Since the human gut is predominately Bacteroidetes and Firmicutes(4) it is thought that a similar ratio could occur in obese humans compared to lean humans. One human study found that prior to a fat-restricted or carbohydrate-restricted diet, obese subjects had less Bacteroidetes and more Firmicutes than the lean control. After their diet, the number of Bacteroidetes increased and Firmicutes decreased as the subjects lost weight(5).
Other research has also indicated that healthy gut bacteria can reduce the likelihood of type II diabetes. The mechanism for this proposal is quite complicated but in short, obesity and type II diabetes can lead to chronic states of inflammation in the body. Reduced Bifidobacterium in the gut due to a high fat diet intake has been associated with higher levels of lipopolysaccharide production(6). Chronic inflammation, minus Bifidobacterium plus lipopolysaccharide production leads to insulin receptors essentially ‘deactivating’, decreasing insulin sensitivity and potentially type II diabetes(6).
How do I promote my gut environment?
Regardless whether our gut bacteria makes us fat, it is important for us to have a healthy gut environment. What the studies are showing us is that the impact of indigestible carbohydrates including fibre can promote positive bacteria growth (1, 7, 8).
Fibre is an amazing macronutrient with many benefits to the human body. Fermentable substrates including indigestible fibre can escape the small intestine and be used for bacterial fermentation. During bacterial fermentation, indigestible carbohydrates produce by-products of short-chain fatty acids (SCFAs)(2). In mice, certain SCFAs have been shown to reduce cholesterol when produced via fermentation as well as reduce the likelihood of weight gain and diabetes/glucose intolerance due to their production (9). Therefore it has been suggested that increasing fibre (both soluble and insoluble) can assist in promoting a healthy gut environment and potentially improving overall health(10).
It is also commonly known that pre- and pro-biotics can be used to promote a healthy gut environment. Probiotics are often advertised and advised to be used after antibiotics in order to restore gut health (3). So what exactly are they? Probiotics are “live microorganisms that when administered in adequate amounts confer health benefits on the host (11)”, in most cases humans. Prebiotics are a form of “non-digestible food ingredients that beneficially affect the host by stimulating the growth and/or activity of one or a limited number of desired bacteria in the colon”(11, 12). Supplementation in humans tends to be in either form of an oral tablet dose of live bacteria or a supplementary food with pre-existing or formulated prebiotics and probiotics such as fermented dairy products (6, 13, 14).
Do I need to pop some pills?
It’s a question that as a pharmacy assistant I often get asked. But what does the research say about the consumption of pre- and probiotics? There are several types of pre- and pro-biotics both available on the market and within research. Below I have looked at one probiotic (Lactobacillus acidophilus )and one prebiotic (fructooligosaccharids), both common in supplementation or diet additions.
Lactobacillus acidophilus is one of the more commonly known probiotics, used in many marketable probiotic products including Inner Health Plus(15), as well as the production of acidophilus milk (6, 16). Several studies have shown that L. acidophilus is effective in reducing the severity of Irritable Bowel Syndrome (IBS) symptoms, regardless of IBS-subtype(17-19).
However what may be more interesting is its potential impact in lowering cholesterol levels and reducing the risk of heart disease. A 2010 review concluded that L. acidophilus does influence lowering cholesterol levels, in particularly LDL cholesterol levels, indicating that L. acidophilus could be used for prevention of heart disease(20). Several other studies have also indicated
There is support for the use of Lactobacillus acidophilus as an effective probiotic however it has shown to be more effective on gastrointestinal discomforts such as diarrhoea, rather than preventing obesity or other related diseases such as heart disease and type II diabetes(6, 11, 16, 20).
Fructooligosaccharides are short chain fructan prebiotics that cannot be digested in the small intestine. Instead FOS are fermented in the large intestine where they have been shown to increase bacterial growth, in particularly Bifidobacterium, and hence increase SCFA production which as discussed can impact on cholesterol levels and diabetes/glucose intolerance (16). FOS have also been shown to influence plasma glucose levels(16). A recent study also found that mice whom were fed with FOS displayed an increase in Bacteroidetes while decreasing the abundance of Firmicutes(9).
So what does it all mean?
Realistically, more studies need to be done. Most research has been conducted in mice which are showing positive correlations between gut health and human health, particularly with the ratio between Fimicutes and Bacteroidetes.
If you believe you need a pre- or probiotic supplement it is always best to speak to a registered dietitians, local GP or pharmacist.
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- Esfahani A, Jenkins DJA, Kendall CWC, Mirrahimi A, Singh N, Villa CR, et al. Gut microbiota, diet, and heart disease. Journal of AOAC International. 2012 2012 January-February//;95:24+. English.
- Diamant M, Blaak EE, de Vos WM. Do nutrient–gut–microbiota interactions play a role in human obesity, insulin resistance and type 2 diabetes? Obesity Reviews. 2011;12(4):272-81.
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- Moroti C, Souza Magri LF, de Rezende Costa M, Cavallini DC, Sivieri K. Effect of the consumption of a new symbiotic shake on glycemia and cholesterol levels in elderly people with type 2 diabetes mellitus. Lipids in health and disease. 2012;11:29. PubMed PMID: 22356933. Pubmed Central PMCID: PMC3305430. Epub 2012/02/24. eng.
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