Preface

Cereal foods constitute a backbone of the diet worldwide and are the major source of energy and nutrients in many populations. The most common way cereal foods are consumed have detrimental effects on human health. The largest proportion of the intake consists of refined-cereal products, generally associated with high glycemic index, reduced nutritional density and central in a dietary pattern associated with increased risk for non-communicable diseases (NCDs). However, shifting the intake towards whole grains is associated with a consistently reduced risk of developing NCDs, specifically cardiovascular disease, type 2 diabetes and certain cancers. In fact, a high whole grain intake is listed as one of the most important modifiable risk factors of NCDs (Global Burden of Disease). Whole grain cereals are rich sources of fibre, many minerals, vitamins and phytochemicals. Public health authorities in the European Union, United States and around the world encourage the increased intake of whole grain cereals based on the health benefits, but recently also for improved sustainability. Most of the evidence for their beneficial effects stem from observational studies, while dietary interventions have shown acute effects on glucose, hormonal and inflammatory responses, and long-term effects on insulin sensitivity, blood pressure and dyslipidaemia. Such effects have been linked to specific bioactive compounds, fibre components, gut microbiota, processing-induced changes and the structural features of whole grains and cereal-grain fractions. The dietary fibre complex, that is, dietary fibre and associated compounds, is believed to have a central role for the health effects of whole grain foods, but the mechanisms are to be elucidated in detail. The development of whole grain cereal foods has a potentially huge positive impact on the health of the global population, but there are important barriers to be torn down to succeed increasing the intake.

Since the first edition of the current book, the number of studies on whole grains and health have increased dramatically. In total, 2093 new publications on the search words whole grain AND health appeared in a Scopus search for the period 1 January 2007 to 26 March 2020. There has been a tremendous development of the field during the past decade, including definition and communication of whole grains to consumers, application of techniques to produce whole grain foods and studies of whole grain health effects. Such advancements are covered and discussed in detail in the different chapters of this book. For example, a large number of epidemiological studies have been carried out in different populations on the associations between whole grain consumption and risk of developing chronic diseases such as CVD, type 2 diabetes, some cancers, but also more rare diseases have been studied. Compared to older studies, more recent observational studies have investigated different grains separately and have also managed to estimate the intakes in g/d. Several large controlled human intervention studies have been conducted to investigate different aspects of whole grains on human health, including effects on cardiovascular and diabetes risk factors such as blood pressure, blood lipids, insulin sensitivity, body weight, body fat and inflammation. During the past decade, new biomarkers of whole grain wheat and rye intake has been developed and validated (alkylresorcinols and their metabolites). These biomarkers have been adopted and shown useful to assess compliance in whole grain intervention studies and they have successfully been used as an independent measure of whole grain intake in observational studies in humans. Metabolomics has emerged as a new approach to address health effects and to find new biomarkers of both dietary exposures and health effects related to whole grain intake. Several metabolomics studies have been published recently to achieve better understanding of health effects underlying whole grain consumption. Such studies have recently shown a modest effect on microbial composition after whole grain/high-fibre cereal intake, which suggested several new mechanisms on why whole grain rye may have particular effects on insulin metabolism. Genomics have been applied in several large-scale intervention studies and have provided new knowledge on how gene expression profiles cause changes in response to whole grain intake. This will be of importance for the overall understanding of the physiological responses in relation to whole grain intake. Moreover, new bioactive compounds in whole grains and whole grain fractions have been identified and are currently studied. One example of such is the group of benzoxazinoids, which have recently been identified in whole wheat and rye grains and in bakery products of these cereals. These compounds, isolated from other sources or synthesized, have been studied for a number of bioactivities. Their uptake and elimination in animals and humans as well as their effects are currently extensively studied. Untargeted metabolomics approaches have facilitated the process of discovering new compounds. The role of gut microbiota for human health and disease has boomed the last 10 years, and important insights on the role of whole grains and dietary fibre and their interaction with gut microbiota for differential responses in human health outcomes have increased dramatically, although there is still much to improve concerning our understanding in this area. EU-regulations on health claims have been adopted with consequences for whole grain consumption. No health claim is allowed for whole grains but several specific claims, including grain components (reflecting beneficial physiological effects and disease risk reduction claims related to certain fibres) are allowed. No current worldwide definition of whole grain intake exists, but new definitions of both whole grains and whole grain products have been suggested.

The structure, outline and style of this book is designed to provide a comprehensive treatise on the subject covering the topic from the grains themselves, their components and distribution in different botanical fractions and products to the effect of whole grains on health and the molecular mechanisms/effects on risk factors underlying their health effects. The book also highlights the interest from the food industry and governmental and non-governmental authorities to develop new food products rich in whole grains as well as to educate consumers about the health benefits of consuming whole grain foods (the whole grain stamp is an example of this communication to the consumer and the whole grain campaigns launched in Denmark and The Netherlands are other examples). The chapters are comprehensive in their coverage with the aim to provide founded knowledge and information for researchers, research students, authority and industry personnel that gives them a multidisciplinary understanding of this important topic.

Recent advances will to a great extent be covered by the update of book chapters of the first edition. As in the previous edition, we divide the book into sections with a slight modification of the suggested sections. More emphasis will be put on the section "whole grains, cereal fibre and chronic disease" and "grain technology and health-related outcomes," whereas consumer aspects are given somewhat less attention compared with the first edition. We also provide comprehensive material on the whole grain morphology constituents, fractions and technology as well as products for readers coming from the medical or public-health sectors. The book comprises 5 sections and concluding remarks and future perspectives. In total, 23 chapters are included (Table 1).

Table 1 Brief description of the content of the sections.

1. Whole grain basics

1. Evidences for disease prevention

1. Whole grains mechanisms and effects on risk factors for chronic disease