Did you know that our immune health starts in the gut?
Inside our bellies, we have an extensive intestinal lining covering more than 4,000 square feet of surface area. Aside from helping us to digest food, it forms a natural barrier and frontline defence system to protect us from infection (1).
The human gut is riddled with bacteria (our gut flora). Our gut flora is a good thing as these friendly bugs compete with harmful microbes for nutrients and physical space.
Our gut flora also releases antimicrobial compounds and communicates with the immune system in complex ways that we are only just starting to unravel.
Maintaining a healthy balanced gut flora can help strengthen our immune responses (2).
One of the best ways to maintain a healthy balance of friendly bacteria (probiotic) in the gut, is to incorporate some fermented foods daily in your diet.
Fermentation is a natural process where microorganisms like yeast and bacteria convert sugars and starches into alcohol or acids; it has been used as a natural method of food preservation since ancient times (4).
Due to their high friendly bacteria (probiotic) content, fermented foods can help support our immune system and reduce our risk of respiratory infections (5,6)
Research suggests that consuming fermented probiotic-rich foods may also help us to recover faster when we are sick (7,8).
The most popular fermented foods include:
One of the best sources of probiotics. Yoghurt is made from milk that has been fermented by friendly bacteria. Make sure that you choose yoghurt with live or active cultures or there will be no probiotics present. Natural unflavoured and unsweetened yoghurt is best. Check the label - as many shop-bought yoghurts are loaded with additional sugar.
Additionally, yogurt may be suitable for people with lactose intolerance. This is because the bacteria turn some of the lactose into lactic acid (9)
Kefir is a fermented probiotic milk drink. It is made by adding kefir grains to milk. It is a better source of probiotics than yoghurt as it generally contains several main probiotic strains.
As with yoghurt, kefir can be well tolerated with those who have lactose intolerance.
Sauerkraut is a finely cut raw cabbage that has been fermented using lactic acid bacteria. It is important to choose unpasteurised sauerkraut when you are buying it as the pasteurisation process kills off the live bacteria
Tempeh is made from fermented soybeans. It is formed into a firm patty and often marketed as a high-protein meat substitute. The fermentation process also produces vitamin B12 (3) which is mainly found in animal products – so it is a particularly good choice for vegetarians.
Miso is a salty tasting Japanese paste. It is made by fermenting soybeans with a type of fungus called koji and salt. It tastes salty and is most often used to make miso soup.
Kombucha (fermented tea)
Kombucha is made from green or black tea that has been fermented with friendly bacteria and yeast.
Pickles or gherkins are cucumbers what have been pickled in salty water and fermented.
Again, make sure you check the label for live cultures - pickles made using vinegar do not have probiotic effects.
What about Probiotic Supplements?
Taking a probiotic supplement is another convenient way to promote a healthy gut flora.
Besides the benefits for our immunity, research also suggests that fermented foods and specific probiotic supplement strains may help improve our digestion (10) blood pressure and heart health (13-14) and even promote good mental health and weight loss (11, 12).
Supplement probiotics and can be particularly beneficial for people with leaky gut and health conditions such as: IBS, rheumatoid arthritis or Chrohns disease where there has been a lot of research suggesting specific probiotic strains can help improve these conditions.
However fermented foods do have the added benefit of often containing many more species of beneficia bacteria than those found in probiotic supplements.
Fermented foods also have the additional benefit of being very nutritious – with most containing key nutrients that are essential for a balanced immune response to infections i.e. vitamin C, iron, B12 and zinc.
There has never been a better time to start adding some fermented foods to your diet!
Where to Buy Them?
Good quality fermented foods can be purchased from many of the large supermarkets and most health food shops, or bought online from good quality suppliers such as McLeods Organics (http://www.macleodorganics.co.uk/) or Wholefoods Online. (https://www.buywholefoodsonline.co.uk/).
With a little time and effort most of them can also be made at home, using fresh ingredients.
Get in touch if you want to know more about making your own fermented foods or to discuss the targeted effect of specific probiotic strains on your particular health condition.
CAUTION – Some cases when fermented foods may need to be avoided/reduced
- A minority of people, usually those with an unbalanced gut flora (dysbiosis) can have a negative reaction to fermented foods – resulting in increased bloating and gas.
** This is usually a temporary reaction - as a result of excess gas being produced as the good probiotic bacteria kill off some of the bad bacteria.
- People who follow a low FODMAP diet for IBS/IBD or who have SIBO (Small intestine bacteria overgrowth) may also find that fermented foods can cause them discomfort.
- Tyramine Intolerance - fermented foods can be high in as substance called tyramine which can trigger headaches in sensitive individuals
- Histamine Intolerance - fermented foods also contain natural histamines. These can accumulate in the body and cause headaches and other symptoms (sinus issues, fatigue, digestive issues) for those who are histamine intolerant
(1) Geuking, M.B., Köller, Y., Rupp, S. and McCoy, K.D., 2014. The interplay between the gut microbiota and the immune system. Gut microbes, 5(3), pp.411-418.
(2) Round, J.L. and Mazmanian, S.K., 2009. The gut microbiota shapes intestinal immune responses during health and disease. Nature reviews immunology, 9(5), pp.313-323.
(3) Denter, J. and Bisping, B., 1994. Formation of B-vitamins by bacteria during the soaking process of soybeans for tempe fermentation. International journal of food microbiology, 22(1), pp.23-31.
(4) Nair, B.M. and Prajapati, J.B., 2003. The history of fermented foods. In Handbook of fermented functional foods (pp. 17-42). CRC Press.
(5) Ozen, M., Kocabas Sandal, G. and Dinleyici, E.C., 2015. Probiotics for the prevention of pediatric upper respiratory tract infections: a systematic review. Expert opinion on biological therapy, 15(1), pp.9-20.
(6) Wang, Y., Li, X., Ge, T., Xiao, Y., Liao, Y., Cui, Y., Zhang, Y., Ho, W., Yu, G., & Zhang, T. (2016). Probiotics for prevention and treatment of respiratory tract infections in children: A systematic review and meta-analysis of randomized controlled trials. Medicine, 95(31), e4509. https://doi.org/10.1097/MD.0000000000004509
(7) Guillemard, Eric, et al. "Effects of consumption of a fermented dairy product containing the probiotic Lactobacillus casei DN-114 001 on common respiratory and gastrointestinal infections in shift workers in a randomized controlled trial." Journal of the American College of Nutrition 29.5 (2010): 455-468.
(8) Boge, Thierry, et al. "A probiotic fermented dairy drink improves antibody response to influenza vaccination in the elderly in two randomised controlled trials." Vaccine 27.41 (2009): 5677-5684.
(9) Gilliland, Stanley E. "Health and nutritional benefits from lactic acid bacteria." FEMS Microbiology reviews 7.1-2 (1990): 175-188.
(10)Ritchie, M.L. and Romanuk, T.N., 2012. A meta-analysis of probiotic efficacy for gastrointestinal diseases. PloS one, 7(4).
(11)Sanchez, Marina, et al. "Effect of Lactobacillus rhamnosus CGMCC1. 3724 supplementation on weight loss and maintenance in obese men and women." British Journal of Nutrition 111.8 (2014): 1507-1519.
(12)Kadooka, Yukio, et al. "Effect of Lactobacillus gasseri SBT2055 in fermented milk on abdominal adiposity in adults in a randomised controlled trial." British Journal of Nutrition 110.9 (2013): 1696-1703.
(13)Khalesi, Saman, et al. "Effect of probiotics on blood pressure: a systematic review and meta-analysis of randomized, controlled trials." Hypertension 64.4 (2014): 897-903.
(14)Sonestedt, Emily, et al. "Dairy products and its association with incidence of cardiovascular disease: the Malmö diet and cancer cohort." European journal of epidemiology 26.8 (2011): 609-618.