Posted on: September 5th, 2023

Lacticaseibacillus paracasei strain Shirota (aka Lactobacillus casei strain Shirota or LcS) is a probiotic bacterium found in various fermented dairy products, including yogurt and other cultured milk beverages. Probiotics are live microorganisms that, when consumed in adequate amounts, can provide health benefits by positively influencing the gut microbiota and various physiological functions.

LcS has exhibited survivability in the GI tract across populations in many different countries. The objective of a recent study published in the International Journal of Food Sciences and Nutrition was to validate this survivability in the United States, where evidence is lacking. Results of the study showed traces of LcS in 23/25 participants.

Why does LcS survive so well in the GI tract of healthy adults?

Lacticaseibacillus paracasei strain Shirota & the GI Tract

The survival of Lacticaseibacillus paracasei strain Shirota (LcS) in the gastrointestinal tract of generally healthy individuals can be attributed to several factors.

Strain Characteristics

The specific strain of LcS (Lacticaseibacillus paracasei Shirota) has been extensively studied for its survival and potential health benefits. Different strains of bacteria can exhibit varying survival and colonization abilities.

Resistance to Acidic Environments

The stomach has a highly acidic environment due to the presence of gastric acids. LcS is known to be relatively resistant to low pH levels, which allows it to survive the acidic conditions of the stomach and reach the intestines where it can exert its beneficial effects.

Tolerance to Bile

Bile salts are secreted in the small intestine and can be harsh on some microorganisms. LcS has been shown to possess tolerance to bile salts, allowing it to survive and pass through the bile-rich environment of the small intestine.

Adhesion and Colonization

Probiotics need to adhere to the intestinal lining to exert their benefits. LcS has mechanisms that enable it to adhere to the mucosal lining of the intestines, which helps it colonize the gut and interact with the host’s cells.


LcS can modulate the immune response of the host. This interaction with the immune system might help it establish a presence in the gut by promoting a favorable environment.

Short Transit Time

The transit time of food through the gastrointestinal tract can impact the survival of probiotics. Fermented milk products, like yogurt, often have a relatively short transit time, which can enhance the chances of probiotics surviving and reaching the intestines.

 LcS has primarily been studied for its potential health benefits and survivability in the gastrointestinal tract. The survival and efficacy of probiotics can vary based on individual factors such as diet, overall gut health, and the presence of other gut microorganisms.

Research at Biofortis

Biofortis is dedicated to protecting consumer health throughout the world by delivering a wide range of testing and consultancy services to the food, supplement, and nutrition industries. Biofortis supports this mission in two ways—through clinical trials and sensory and consumer insights testing. We specialize in clinical research targeting foods, ingredients, and dietary supplements that affect body structures, function, and overall health. Contact us with any clinical trial or scientific consulting needs.

Source: The probiotic Lacticaseibacillus paracasei strain Shirota (LcS) in a fermented milk beverage survives the gastrointestinal tract of generally healthy U.S. Adults. Published in the International Journal of Food Sciences and Nutrition August 16, 2023.

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