Cookbook sections of book stores are filling up with books on how to ferment rather than how to cook. The yogurt section in the supermarket is now laced with special ‘probiotic’ yoghurts, which apparently have further benefit over other yoghurts. What is all the fuss about fermented foods, probiotics and prebiotics anyway? Should everyone be encouraged to eat and drink fermented foods?
There are a few different terms being thrown around here so let’s get things straight;
- Fermented foods have undergone a process in which bacteria or yeast convert carbohydrates to carbon dioxide and alcohol or organic acids (e.g. lactic acid).Brown, A., Understanding Food Principles and Preparation. Fifth ed. 2015, Stamford, CT: Cengage Learning. Examples are yoghurt, sauerkraut, kimchi, tempeh, miso, kombucha, sourdough bread, cheeses, beer and wine… the list goes on. Let’s remember that not all fermented foods are created equal in terms of health benefits!
- Probiotics are “live microorganisms that confer a health benefit on the host when administered in adequate amounts”. Common probiotics include the genera Lactobacillus and Bifidobacterium.
- Prebiotics are “food components that are not digested in the small intestine but are used instead as food by bacteria to encourage their growth”.Rolfes, S.R., et al., Understanding Nutrition: Australian and New Zealand Edition. 2 ed. 2014, Australia: Cengage Learning Australia Pty Limited. Examples of prebiotics are fructooligosaccharides (FOS) and inulin -think bananas, onions and garlic.
Did you know that there are just as many, if not more, bacterial cells in our bodies than there are human cells? Our method of birth, medications (e.g. antibiotics) and diet affect the composition of microbial strains that live in our gut, which can then have an effect on our risk of common infectious diseases and intestinal function. The human microbiome is a hot research topic; the United States National Institutes of Health is conducting the Human Microbiome Project (HMP), which aims to characterize all of the microbes in the gastrointestinal tract, nasal passage, oral cavity, skin and urogenital tract. The information gained from the HMP is used to examine the role of these microbes in human health and disease.
What do we know?
Probiotic bacteria promote gastrointestinal functions including immune response regulation, epithelial barrier function and cellular proliferation.Vitetta, L., et al., Probiotics, prebiotics and the gastrointestinal tract in health and disease. Inflammopharmacology, 2014. 22(3): p. 135-54.Bermudez-Brito, M., et al., Probiotic mechanisms of action. Ann Nutr Metab, 2012. 61(2): p. 160-74. There is not yet evidence to show a cause-and-effect relationship between the composition of our microbiota and the pathogenesis of diseases, however, there are definite associations between an altered microbiota and obesity, inflammatory bowel disease, irritable bowel syndrome, non-alcoholic steatohepatitis, the metabolic syndrome, atherosclerosis, type 1 diabetes, autism, allergy, asthma and coeliac disease.Sanders, M.E., et al., An update on the use and investigation of probiotics in health and disease. Gut, 2013. 62(5): p. 787-96. Yep, a lot of diseases!
Eating fermented foods doesn’t necessarily mean eating probiotics. Many fermented foods lose their viability during processing. Oxygen, pH and temperature (especially heat above 60˚C) are stressors that reduce the survival of probiotics. For example, most breads are not probiotic because the heat reduces the viability of the microbes used in fermentation. The human digestive system also puts probiotics through a rigorous test! The acidity of the stomach and digestive enzymes knock out many of the microbes travelling through the gastrointestinal tract; those that survive may recover in the small intestine and continue to grow in the large intestine.
Two sides of the story…
Although there are many benefits of probiotics and a healthy microbiota, there have been some studies to show that a high intake of pickled vegetables may increase the risk of gastric cancer. Of course we also know that a high intake of alcohol is detrimental to health. Many fermented foods, especially fermented vegetables and cheeses, have a high salt content. The World Health Organization strongly recommends adults consume no more than 5g salt per day (<2g/day sodium) to reduce blood pressure and risk of cardiovascular disease, stroke and coronary heart disease. Severely immunocompromised patients are more susceptible to bacteraemia and fungaemia (not as ‘fun’ as it sounds); probiotics may increase the risk of infection and, therefore, have not been considered safe for this population.
The final word
Research has uncovered many benefits of fermented foods and probiotics for immunity, gut function and wellbeing. It is safe to say that fermented foods can be a healthy addition to a balanced diet in generally healthy people, however they are not all created equal and it is important to keep an eye on the salt and alcohol content. Go for variety!
References [ + ]
|1.||⇪||Brown, A., Understanding Food Principles and Preparation. Fifth ed. 2015, Stamford, CT: Cengage Learning.|
|2.||⇪||Rolfes, S.R., et al., Understanding Nutrition: Australian and New Zealand Edition. 2 ed. 2014, Australia: Cengage Learning Australia Pty Limited.|
|3.||⇪||Vitetta, L., et al., Probiotics, prebiotics and the gastrointestinal tract in health and disease. Inflammopharmacology, 2014. 22(3): p. 135-54.|
|4.||⇪||Bermudez-Brito, M., et al., Probiotic mechanisms of action. Ann Nutr Metab, 2012. 61(2): p. 160-74.|
|5.||⇪||Sanders, M.E., et al., An update on the use and investigation of probiotics in health and disease. Gut, 2013. 62(5): p. 787-96.|