Microbial combination of gastrointestinal tract and microbes entered to GI tract via food can have useful or harmful effects on health. Several evidences indicate that some bacteria are used for fermentation of dairy products such as yogurt and a number of specific and fruitful microbes of GI tract have powerful anti- pathogenic and anti- inflammatory effects. These microbes cause promotion of body resistance against various types of pathogenic microbes which can treat and prevent from outbreak of diseases as a result of growth and reproduction of these pathogenic microbes. “Probiotic” products include fruitful bacteria which stay in intestine after consumption and leave fruitful effects in human health.

The term “probiotic”, which has a Latin terminology meant “life”. World Health Organization (WHO) defines this term to “Live Organisms”. If probiotic is used properly, it can leave “health” parameter for its host.

As a matter of fact, probiotics are consumed in the following two forms:

  • As food supplement in the form of powder, syrup or pill,
  • As food enriched with probiotics, for example, if probiotic bacteria are used in production of any fermented dairy product such as yogurt, the product is called “probiotic”.

Yogurt is a highly traditional consumed food which contains considerable amounts of probiotics. “Lactic Acid” is used for production of yogurt which causes fermentation of milk and conversion of lactose sugar to lactic acid.

Development of application of probiotics has offered new approaches on their role in health and prevention of diseases in order to reduce microbial combination of gastrointestinal tract.

Many studies have shown fruitful and therapeutic effects of probiotics in human intestine. Hereunder, the most important evidences will be discussed with relation to the consumption of yogurt and various types of “Lactic Acid” bacteria used for fermentation of milk and valuable therapeutic effects of them especially on the performance of gastrointestinal tract performance and prevention of diseases.

Nutritional Value of Yogurt

Combination of yogurt nutrients is the same combination of milk nutrients which has changed under the influence of type and duration of fermentation and type of used microbes partially

Vitamins Group “B”

Principally, process of fermentation will cause reduction of milk vitamins as compared with its mineral, because, vitamins are more susceptible than minerals in terms of environmental change.

The most important factors which lead to reduction of vitamins include as follows: temperature and pasteurization, ultrafiltration, mixing and oxidative conditions. Moreover, type of microbial culture used for fermentation is effective for reduction of milk vitamins.

Species of “Lactic Acid” bacteria need vitamins of Group “B” for growth and reproduction, the most important of which are vitamin “B12”. Some species of the bacteria are able to synthesize “B12”. Therefore, accurate selection of bacteria specifies used for fermentation can be considered as an important fact in line with prevention of considerable reduction of “B12”.


Dairies are the most important source for providing lactose sugar. Before fermentation, the amount of lactose in milk is almost 5 percent. “Lactic Acid” bacteria turn lactose sugar into lactic acid. Therefore, acidity property of yogurt is more than milk.

For this purpose, people who suffer from intolerance of lactose can tolerate yogurt better than milk.


Usually, amount of protein in factory- made yogurts is more than milk, because, some fat- free powdered milk is added to yogurt in production of yogurt for firmness (consistency). There is a common concept that yogurt protein is digested easier than milk, because, fermenting bacteria carry out the initial stages of digestion of protein. With increased time of preservation of yogurt, its protein can be digested better. During fermentation, both temperature and acid production is led milk casein to be congealed. Therefore, yogurt proteins enjoy high bio quality as compared with milk proteins.


Milk fats face change during fermentation. It is shown that concentration of linoleic acid in yogurt is more than that of milk. This fatty acid has stimulating property of body immune and anticancer system. In a new study conducted on breast and intestine cancer, effects of this fatty acid has been observed in reproduction of cancerous cells.


Yogurt is a good source for calcium and phosphor. In other words, yogurt is rich in calcium and phosphor. As a matter of fact, yogurt, milk, cheese and other dairy products provide main part of requirement to calcium in our daily diet. Calcium and magnesium of yogurt is absorbed easier than milk due to its acidity. Therefore, yogurt is highly recommended to women in menopausal period who are at high risk of bone and osteoporosis disorders.

Mechanisms Presented on Potential Advantages of Yogurt on Performance of Intestine

Microbial Composition of Intestine

Lactobacillus is one of the microbes existing in microbial composition of small- and large intestine. Ability of prevention of growth of pathogenic bacteria in intestine is one of the most important properties of lactobacillus. On the other hand, various species of “Lactic Acid” bacteria enjoys different ability for survival in gastrointestinal environment.

Immunological Responses of Intestine

Lymphoid tissue of mucus part of gastrointestinal tract is considered as the first defensive line against eaten pathogenic microbes. Studies have shown that “Lactic Acid” bacteria will lead to the promotion of immunological performance of lymphoid tissue of GI tract. Creation of low acidity, production of organic acids, carbon dioxide, peroxide hydrogen (as main killing factor of bacteria), ethanol, consumption of nutrients and competing for physical environment by these bacteria are of the effective factors in this respect. Also, studies have shown that edible consumption of “Lactic Acid” bacteria through consumption of yogurt will cause increase of secretion of immunoglobulin “A” and also increased number of its secreting cells in small intestine of mouse. It should be noted that immunoglobulin “A” has a basic and fundamental role in controlling pathogenic bacteria in intestine.