The GI tract is probably one of the body's most microbiologically dense places. It is home to trillions of bacteria. There can be as much as 3-4 pounds worth of bacteria in just the GI tract.
Probiotics are live microorganisms that, when consumed in proper doses, can provide a health benefit. Most probiotics are the same bacteria that reside in the gut, especially lactic acid bacteria. Most people consume probiotics in both supplement form as well as in foods rich in probiotics (fermented foods such as sauerkraut, kimchi, kombucha tea, and kefir).
Animal studies show the benefits of probiotics in improving the outcome of various infections. While more research is needed for humans, there are encouraging results seen in the role probiotics play in several health conditions (diabetes, bacterial infections, IBS, and others). After all, probiotics are bacteria that are essential for immune cells to mature and to function. In essence, healthy gut bacteria "train" the immune system on how to respond to different infections.
How exactly do Probiotics Act?
There are several proposed ways that probiotics work. They may:
- stimulate and signal the immune system to activate it. They do this by interacting with certain cells of the intestinal wall.
- strengthen the intestinal barrier lining by increasing production of a protective mucus layer. They also may stimulate the production of proteins that act like the mortar or concrete between bricks, keeping the cells of the intestinal wall tightly together and preventing any gaps.
- controlling the balance and growth of potentially infectious bacteria in the gut
- influence the activity of not only gut immune cells but also immune cells of other parts of the body. Research has shown evidence of this in the spleen, bronchi, and mammary glands.
- the by-products of probiotic bacterial fermentation can play a role in immunity. One example is tryptophan. When probiotic bacteria decompose this amino acid, they produce various metabolites or by-products that can reduce inflammation, or, as one study showed, reduce the ability of pathogenic bacteria like E.Coli from even adhering to cells to infect them. It can also produce by-products that activate immune cells.
- Interestingly, individuals who are underweight or obese (as our previous article highlighted) can have a compromised immune function. Probiotics have been shown to help increase the immune response in such individuals.
Probiotics for Better Health
One simple way to incorporate more probiotics in your diet is to eat more fermented foods. As listed above, kimchi, kombucka, kefir, and sauerkraut are some of the top foods containing probiotics. Aim for at least 1 serving per day. Other foods include tempeh, miso, and probiotic yogurt.
Check with your doctor about incorporating a daily probiotic supplement. However, before beginning a probiotic supplement, aim to include more prebiotic foods. Prebiotics are foods that feed the probiotic bacteria in your gut.
Support the probiotics that are already naturally present in your digestive tract by eating a diet rich in whole foods. A highly processed diet, especially with foods that contain antibiotics from dairy and meats, can significantly mess up the balance of good bacteria in your gut.
Healthy gut bacteria LOVE fiber. Eat a diet with plenty of fiber-rich foods, such as fruits, vegetables, and whole grains. Some of the most prebiotic-rich foods include onions, leeks, asparagus, artichokes, legumes, garlic, and whole grains.
If and when you do decide to buy a probiotic supplement, just make sure to check the proper dosage, specific strains you are looking for, and proper storage guidelines to keep them alive.
References
Ann Nutr Metab 2019;74:115–124
Hooper, L. V., Littman, D. R., & Macpherson, A. J. (2012). Interactions between the microbiota and the immune system. Science (New York, N.Y.), 336(6086), 1268–1273. https://doi.org/10.1126/science.1223490
T. Bansal, R. C. Alaniz, T. K. Wood, and A. Jayaraman, “The bacterial signal indole increases epithelial-cell tight-junction resistance and attenuates indicators of inflammation,” Proceedings of the National Academy of Sciences, vol. 107, no. 1, pp. 228–233, 2010.
Zhang, C., Wang H., & Chen, T. (20 Nov 2019) Interactions between Intestinal Microflora/Probiotics and the Immune System Shanghai, China: BioMed Research International. vol 2019, 1-8.