Preface

In recent years, the microbiome and its impact on health has become an area of great scientific interest. There are many microorganisms present in the human body, and these are mainly located in the gut. Generally, there are two types of microorganisms in the gastrointestinal tract: "good" and "bad." Good microorganisms are called probiotics, which are living microbiota cultures that enhance the qualities of the indigenous microbiota when supplied to the host. These bacteria are widespread in nature and are suitable for usage in food industries. *Lactobacillus* is one of the earliest probiotics proven to have a beneficial impact on health. Probiotics enhance epithelial barriers, increase adherence to gut mucosa and microbial adhesion, generate antimicrobial compounds and regulate the immune system, and can be used as food supplements to manage several gastrointestinal tract diseases. They are also used in research studies to develop commercial probiotic foods. Therefore, a perfect and sensitive balanced interaction of microbes with the host is required for a healthy body. Any disturbance in that balance leads to dysbiosis and the host may become more susceptible to disease.

This book discusses the effect of microbiota on human health. Microbiota is the powerhouse of health and disease. Moreover, the microbiome contains the genetic information and the genomes of the microorganisms themselves. It is now well known that the microbiome interacts with its host and is involved in basic human biological processes, modulating the metabolic phenotype in the bioconversion of nutrients and detoxification, influencing innate immunity, and protecting against microbial infections. The microbiome is also known for producing many vitamins such as vitamin B12, thiamine, riboflavin, and vitamin K, which is required for blood coagulation. Generally, the gut microbiota construction is determined by several factors, including gestational pathologies, type of birth, type of feeding, prenatal and perinatal use of antibiotics, complementary feeding, and environmental pollutants. From gestation to the first two years of life, these events influence the establishment of the microbiota. Hence, microbiota affects the metabolic and immune response and has a subsequent impact on human health.

As an alteration in the microbiome can be protective or causative, this book reviews the pathogenesis and potential roles of some members of microbiota in diseases such as inflammatory bowel disease (IBD) disease and presents a promising strategy to alleviate and cure this condition. It also examines the relationship between gut microbiota imbalance and how defects in this dysbiosis can lead to disease. Moreover, the book discusses microbiota potential in type 2 diabetes, highlighting recent findings in the regulation of extraintestinal metabolism by gut microbiome with emphasis on the physiology and pathophysiology of the pancreas in health and disease. The microbiome also plays a major role in the development of obesity by regulating energy metabolism. The makeup and density of intestinal flora can be influenced by diet. As such, this book examines the relationship between the gut microbiome and obesity. It also examines the role of gut microbiota in promoting the development and progression of brain health. The interactions of the gut microbiota and brain axis

have been studied using various animal models. However, most of the animal research has only been able to reveal the fundamentals, such as the diversity of the microbial community, the potential microbial pathways, and the dysbiosis of the gut microbiota due to diet and drugs. Finally, the book reviews the development of functional food fortified with probiotic microorganisms, such as fermented dairy products (yogurt, fermented beverages, and others), which have a positive impact on the gut microbiota balance. Probiotic fermented milk should contain at least 107 CFU/mL of live bacteria at the time of consumption to obtain health benefits.

> **Hoda El-Sayed** Associate Professor, Dairy Department, Food Industries and Nutrition Research Institute, National Research Centre, Cairo, Egypt

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Section 1

Microbiota and Health

Section 1
