Immunonutrition: Interactions of Diet, Genetics, and Inflammation PDF

Preface

Immune function and nutrition are closely intertwined in human health. The immune system is composed of an innate immune system and an adaptive immune system. The latter is only found in vertebrates while the former is an ancient system that goes back in evolution to insects and plants.

It is the innate immune system that is overactivated in response to the Western diet and obesity-associated diseases due to chronic low-grade inflammation. These diseases range from type 2 diabetes to heart disease, which are closely aligned with the accumulation of visceral and liver fat resulting in insulin resistance. Individuals who are about 30 lb overweight or have a body mass index (BMI) of 30 or more have a 30-fold increased risk of type 2 diabetes mellitus. This 3000% increased risk is not simply another risk factor but an intrinsic part of the pathogenesis of diabetes bringing us to call this condition diabesity. However, the etiology of diabetes is not simply linked to weight but to visceral fat. Individuals in India and China can accumulate visceral fat at normal or even low BMI. Some 70 million Americans have high blood sugar or prediabetes, and the syndrome, called metabolic syndrome, affects 50% of individuals between the ages of 50 and 65 in the United States and many other countries.

The interaction of immune function and nutrition underlies the low-grade chronic inflammation involved in the etiology of many of the common age-related chronic disease conditions covered in this textbook. The largest portion of the immune system is located adjacent to the gastrointestinal tract. Plants, which also have an innate immune system, live in soil that is made up of both friendly and potentially toxic bacteria. Plant roots attract helpful bacteria and repel those bacteria that could attack them. Humans carry their soil with them in the form of trillions of gut bacteria, which interact with the immune system. Both dietary intake and obesity influence the gut microflora, called the microbiome. Plants affect the local bacteria in the soil; it is thus not surprising that dietary phytochemicals and prebiotics in the human diet also affect gut microflora.

Diet and exercise are necessary strategies in efforts to reduce visceral fat and modulate systemic immune function through increased intakes of fruits, vegetables, plant protein, fish oils, prebiotic fibers, and spices. Nutrition in the broadest sense determines the health of the immune system. When malnutrition results in death, it is most commonly caused by infections due to loss of immune function. Therefore, both in obesity and malnutrition, nutritional factors influence immune function. This close interaction is the genesis of the term immunonutrition, which represents a new interdisciplinary field of nutritional and medical research.

It is our hope that this textbook will stimulate increased interest in this new interdisciplinary field among students and junior investigators who will carry this field into the future. There is a need for more human studies to complement the exciting basic research already developed in cell culture and animal models demonstrating the mechanisms underlying the interaction of nutrition and immune function. We hope that this book will achieve these objectives.