Probiotics : how does it affect our health?

Sammanfattning: The human body consists of about 10 times as many bacteria as our own body cells. Only the gastrointestinal tract can hold up to 400 different bacterial species, where the majority of the bacteria are concentrated to the large intestines. We are born sterile without any microbiota, but thereafter colonizing and development of the microbiota occur over time. Probiotics are good bacteria that are supplied via food or as dietary supplements. The most common of probiotic bacteria belongs to the genera Lactoba-cillus or Bifidobacterium. They are classified as safe bacteria which makes them very popular to use in probiotic products. Both genera are Gram positive, rod-shaped and can ferment carbohydrates to short-chain fatty acids that lower the pH and make it unfavorable for other bacteria. Some guidelines for probiotics are that it must contain live bacteria and be resistant to gastric acid and bile salts. In this literature study focus has been on how probiotics affect the gastrointestinal tract which in turn can affect the health. To narrow down the work four different probiotic strains that are common on the Swedish market have been selected for fur-ther studies: Lactobacillus reuteri Protectis DSM 17938, Lactobacillus rhamnosus GG (LGG), Lactobacillus plantarum 299v and Bifidobacterium animalis BB-12. The general mechanism of action for probiotic bacteria is that they temporarily can persist in the intestine and be able to produce antimicrobial substances that can inhibit pathogenic bacteria. Probiotic bacteria should also be able to compete with other bac-teria about nutrition and bind to epithelial cells to strengthen the immune system. Studies have shown that Lactobacillus rhamnosus GG reduces the risk of suffering from antibiotic-associated diarrhea both in children and adults and that Lactobacillus reuteri DSM 17938 reduces the time of crying with 30-70 minutes per day in infants with colic. Analyzing the effect of probiotics is a challenge as the effect can vary widely from individual to individual. Also, most studies vary greatly in performance, duration and dose given to patients. There are also more studies on mono strained probiotics than on multi strained. Due to the fact that multi strained probiotics makes it more difficult to evaluate which strain has had the best effect the studies are harder to compare. Since probiotics are classified as safe and harmless bacteria it can always be a good start to treat gut dysbiosis with probiotics.