Carotenoids in Health and Disease PDF

Preface

This volume is a collection of chapters by leading carotenoid researchers depicting the role or roles of carotenoids in human health and disease. The first multiauthored book on carotenoids, edited by Otto Isler of Hoffman-La Roche and published in 1971 (1), consisted of 12 chapters dealing primarily with different aspects of carotenoid chemistry. Only one chapter addressed the function of carotenoids (2). Since then, interest in carotenoids has shifted from the chemistry of this interesting class of compounds to their actions in plants, animals, and humans. We know that carotenoids have an important role in photosynthesis, and two excellent volumes devoted to this topic have been published (3, 4). However, there has not been a book devoted to the role of carotenoids in health and disease until this one. Although individual articles have been published in an attempt to present this material, sufficient information is now available to warrant publicaton of a comprehensive text. One of our reasons for compiling a volume devoted to carotenoids in health and disease was to put into a clear perspective the results of observational epidemiological studies, clinical studies, and intervention trials involving carotenoids that are continuing to this day. For example, what was intended to be an evaluation of the role of ß-carotene in lung cancer prevention appears to have resulted in the demonstration of a unique relationship between high-dose ß-carotene supplementation, smoking, and elevated cancer risk. This observation, which was totally unexpected, has led to new studies and observations to explain these unusual results.

But there is much more to carotenoids than ß-carotene. Of the more than 600 carotenoids identified in nature, as many as 50, all of which may have differing biological activities, may be included in a typical human diet. This poses a serious challenge to investigators, particularly as they try to tease out the effects of individual carotenoids from the mixture that normally occurs in foods. Recent research has shown that risk of several chronic diseases is inversely related to the vii intake of dietary carotenoids. This deserves a very careful evaluation because carotenoids are a particularly widespread dietary component, thus if they are related to disease prevention, it should be relatively easy and inexpensive to alter the diets of individuals potentially susceptible to such diseases. These issues are addressed in several chapters in this volume.

Several carotenoids in addition to ß-carotene deserve particular attention with respect to health and disease prevention. One is lycopene, the major pigment present in tomatoes and tomato products, which has been associated with a decreased risk of several cancers such as prostate cancer. In addition, the oxygen-containing (xanthophyll) carotenoids lutein and zeaxanthin (the major pigments in the macular region of primate eyes) have been proposed both as markers for age-related macular degeneration and as possible therapeutic agents to prevent this disease. For these carotenoids, clinical studies and intervention trials are underway to evaluate the validity of these relationships.

One may ask why a book is necessary for a class of compounds that have never been identified as being essential for humans. We are aware that no study has indicated that individuals placed on a completely carotenoid-free diet have experienced deficiency symptoms. But we may be well beyond deficiency symptoms when we deal with compounds such as the carotenoids or other families of plant products. There is compelling evidence that several of our dietary carotenoids exert profound effects on cellular processes when added to cell cultures at human physiological levels. Several chapters in this book describe these actions and give guidelines for what we may expect to find in humans. There are certainly strong suggestions that carotenoid intake is associated with ‘good health.' But is this due to the carotenoids or to other components of the foods in which the carotenoids are present? We may be years away from answering this question, but we will do our best to present the current state of science in the field.

We are grateful to our authors for their contributions to the evaluation of carotenoids in human health and disease.