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1 :Introduction The nutrition and food sciences are among the most interdisciplinary of all sciences. They bring together the chemical, physical, biological, medical, agricultural, social, behavioral, and engineering sciences to ex- amine how food affects health from the basic molecular and cellular levels to the organ, organism, and even population levels. Another major area of study in these fields is how food systems can be designed to enhance the physical and economic well-being of indivicluals and groups, as well as the adequacy and safety of their food supply. Progress in the nutrition and food sciences has accelerated dramatically during this cen- tury. We have moved from defining the chemical nature and biological role of macronutrients (carbohydrates, fats, and proteins) to discovering vitamins, minerals, and other biologically active food constituents and now to establishing a scientific basis for the role of food and dietary patterns in long-term health. Various technological achievements have enabled scientists to conduct research more effectively and to develop a more abundant and health-promoting food supply. As we approach the twenty-first century, the nutrition and food sci- ences will be profoundly affected by the rapid advances being made in molecular biology. Understanding the molecular and genetic aspects of health and disease and how food components modulate biological pro- cesses and the expression of our genetic makeup will continue to be a significant, possibly the predominant, component of the health-related research of the new century. Research findings are likely to play a critical 15
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16 OPPORTUNITIES IN THE NUTRITION AND FOOD SCIENCES role in developing strategies to prevent and manage genetically and envi- ronmentally governed diseases. Therefore, nutrition and food scientists, academic educators and administrators, and public- and private-sector policymakers need to consider the trends developing in these disciplines, their research needs and opportunities, the adequacy of education and training programs for researchers and practitioners, and the speed with which knowledge in the nutrition and food sciences is being transferred from science into policies and practice. WHO WE ARE AND WHAT WE STUDY Research in nutrition in the early part of this century was focused almost entirely on discovering essential nutrients and characterizing their physiological and biochemical roles in the body. Researchers used a unique method of determining essential nutrients and their requirements the animal growth model that was unique to nutrition. More than 40 years ago, the first issue of the American Journal of Clinical Nutrition defined nutrition as "the cornerstone of preventative medicine, the handmaiden of curative medicine and the responsibility of every physician." Almost two decades later, in the same journal, Alfred Harper suggested that nutrition be called an "integrating science," or per- haps an "applied science," since it is concerned with solving practical problems. Harder added. "There is no such thing as a nutritionist there , ~ , 1 1 0 art? nlltritinnist.~. We Bra nh~mi~t~ hir~r~hPmictc nh`7cim1r>~i~tc nothr~ln 1 . 1 ~ In .... ~ ~ ~
INTROD UCTION Food Supply Agriculture Animal husbandry Environmental waste management Food engineering Food processing Food production Food toxicology 17 Within Cells or In Vitro Environments Analytical chemistry Biochemistry Cell biology Immunology Molecular biology Molecular genetics Populations Anthropology Demography Ecology Economics Education Epidemiology Food and health policy Political science Sociology - Specific Organ, Entire Human or Animal Animal nutrition Clinical sciences Medical genetics Medical and special foods Pathology Physiology Psychology Physiological chemistry FIGURE 1.1 One illustration of the scope and coverage of the nutrition and food sciences. Each box represents one focus of the nutrition and food sciences with examples of areas of study. The areas of study listed are examples; many of them could be placed in more than one box. "food science" and refer to both as disciplines or fields of study. We concur with Harper that they are integrating, applied disciplines that ap- ply knowledge about food and nutrients and their effects on health de- rived from the basic chemical, physical, biological, medical, social, behav- ioral, and engineering sciences to improve human well-being. To prepare a readable report of reasonable size, we have had to be selective rather than encyclopedic in our coverage of the nutrition and food sciences. Many topics within the purview of these diverse disciplines, such as those relating to agriculture or the environment, receive little or -
18 OPPORTUNITIES IN THE NUTRITION AND FOOD SCIENCES no attention. In addition, we have focused on the United States in exam- ining research opportunities, issues of training and support, and applica- tions of research to public policy. THEME S Chapters 3 through 6 identify what we consider to be among the most promising directions for research in the nutrition and food sciences to improve human health and ensure the vitality and importance of these disciplines into the next century. Most of our research recommendations can be encompassed by five themes. These themes, described below, inte- grate the remaining chapters in this report and provide a basis for devel- oping the major components of a national research program that we pro- pose in Chapter 9. Uniting these themes is the underlying premise that our long-term health is determined by both genetics and environment. The environment as used here includes diet and other life-style factors (including both health-promoting and risk-taking behaviors) in addition to physical and chemical exposures (such as ionizing radiation and toxic substances in the workplace). For the majority of Americans who do not smoke, do not drink excessively, and are not exposed to environmental hazards in their work, the food they eat is the largest controllable factor determining their long-term health. Theme 1: Nutrients and Biologically Active Food Constituents in Development, Cell Differentiation, Growth, Maturation, and Aging Understanding how nutrients and other biologically active compounds in food influence human development from conception to death has been and remains a fundamental line of inquiry for the nutrition and food sciences. Research in these areas has led to the development of the Rec- ommended Dietary Allowances (RDAs), which have been established for groups of healthy individuals of both sexes and different ages as levels of intake of essential nutrients judged to be adequate to meet known nutri- tional needs. RDAs have been revised periodically to include new re v ~ , search results. Research is showing, for example, how retinoic acid, a derivative of vitamin A, affects the expression of specific genes that regulate cell divi- sion en cl differentiation (whether a cell, for example, becomes a liver cell or epithelial cell on the inside of the mouth). In addition, carotenoids (found in fruits and vegetables; several have provitamin A activity) seem to enhance communication among cells, which may reduce the risks of
INTROD UCTION 19 cancer, characterized by uncontrolled cell division. Scientists are discov- ering how malnutrition during critical periods in early (levelopment- before birth or during the first three years thereafter can compromise normal growth and development throughout childhood and into adoles- cence. They are learning how peak bone mass can be achieved with the help of dietary patterns that include adequate calcium and other nutri- ents, thereby lowering the risks of osteoporosis in later life. Not only are nutrients necessary for development, but they may also be used to extend human life. Research suggests that the aging process and risk of diseases such as heart disease and some cancers are amenable to influence by antioxidants. Nutrients with antioxidant properties such as vitamins C and E and selenium, as well as carotenoic3s and possibly other nutrients and food components help protect the proteins, lipids, and DNA in cells on which most of our basic life processes (depend from damage by oxygen. Scientists are just beginning to learn how nutrition can affect the ability of the immune system to protect us against infectious diseases and influence our risk of developing chronic degenerative diseases. Tests to determine how well the immune system responds to various challenges may become very sensitive tools to measure a person's nutritional status. Theme 2: Genes, Food, and Chronic Diseases Over the past half century, scientists have investigated the role of dietary patterns, specific foods, and nutrients in maintaining health and reducing the risk of developing chronic diseases such as heart disease and cancer. Laboratory, clinical, and epiclemiological research has enabled them to identify dietary constituents that influence specific diseases and their underlying biological mechanisms. As a result, nutrition scientists have developed dietary guidelines that not only help ensure nutritional ad- equacy, but offer some protection against the diseases that kill most people in the United States. As we learn more about how genetic factors influ- ence specific diseases and their underlying mechanisms, dietary guide- lines will likely be modified to incorporate our knowledge of the interac- tions of genes and diet. At some point in the future, it may be possible to individualize dietary guidance through knowledge of a person's genetic endowment and lifestyle. At the present time, dietary guidelines are di- rected to most of the U.S. population to help protect the largest number of people from diet-related chronic diseases. Perhaps the most significant new development in nutrition science is the growing understanding of the role of diet and hormones in regulating the expression of our genetic endowment. Dietary patterns interact with genetic predispositions to alter the risk of disease. Using the techniques of gene transfer with animals and with cells in culture, it will be possible to
20 OPPORTUNITIES IN THE NUTRITION AND FOOD SCIENCES learn the mechanisms by which specific food constituents interact with DNA to cause or affect disease processes. These basic studies can then be related to applied clinical questions. For example, studies of twins and aclopted children strongly suggest that obesity has a genetic component, as do studies of the Pima Indians, whose rates of obesity and diabetes are among the highest in the worIcl. But studies of primitive peoples who undergo rapid modernization provide strong evidence that changed cli- etary patterns ancI lifestyles also affect powerfully the risk of disease, since the spectrum of diseases in these peoples changes much more rapidly than can be accounted for by genetic accommodations. Theme 3: Determinants of Food Intake A person's food selections and dietary patterns are profoun(lly influ- enced by a variety of metabolic, sensory, cognitive, cultural, and economic factors. Although genetic and physiological factors shape individual food preferences and aversions, the translation of these into behavior diet selection is mediated by a variety of sociocultural factors. The study of nutrition ant! behavior has traditionally dealt with the impact of foods or nutrients on brain function and their subsequent influences on behavior. Less attention has been pair] to the ways in which behavior influences nutritional status. In fact, until recently, research on food preferences and choices and the selection of a habitual diet was often regarded as periph- eral to the nutrition and food sciences. We need to conduct much more multiclisciplinary research into the relationships between food intake, nutritional status, and behavior. The results of this research should enable us to develop strategies to help more people to follow dietary guidelines. At the basic biological level, we need to unclerstand how neurotransmitters function and how they influ- ence appetite and food choice. While genetic and physiological factors may shape individual food preferences and aversions, socioeconomic anc3 cognitive factors definitely do. Learning how all of these factors interact to determine what and how people eat is a challenging, long-term oppor- tunity for research in the nutrition and food sciences. Theme 4: Improving Food and Nutrition Policies Food and nutrition policies and programs rely on research for their formulation, implementation, and evaluation. The essential components of a comprehensive policy on food and nutrition includes (1) the availabil- ity of adequate food for everyone, (2) a high-quaTity, safe, and wholesome food supply, (3) consumer education about dietary patterns that promote health and prevent disease, (4) opportunities for individuals to put their
INTRODUCTION 21 increased awareness and improver! dietary knowledge to practice, (5) ac- cess to nutrition services within the medical care system, and (6) effective food assistance programs for those in need. To improve policy formulation, we need to determine what combina- tion of social ancl economic indicators best predicts an inclividual's need for help in obtaining food. We also need to develop a uniform under- standing of what constitutes desirable dietary behavior. For policy imple- mentation, it is important to learn how to deliver nutrition information to people in such a way that they will act upon it and on identifying the most appropriate strategies for changing the eating behavior of subpopulations. Implementation also depends on learning what incentives will prompt producers and processors to modify the food supply to meet health con- cerns while simultaneously maintaining its quality, safety, acceptability, and profitability. We also need research on better ways to evaluate the effectiveness of programs by government and others to provide food to those in need or to improve eating habits. Theme S: Enhancing the Food Supply Food science and the food industry are responding to emerging re- search findings, consumers' changing dietary preferences, and government policies by providing a wide variety of foods reduced in calories and mocli- fied in fat, cholesterol, and salt content. Enhancing the food supply in- volves producing health-promoting, high-quality, economical, and whole- some foods with reclucec3 adverse effects on the environment and better use of raw materials. Challenges facing the food industry are to continue to conduct re- search to develop better products; minimize microbiological and chemical contamination of food products; minimize the environmental impacts of food production and processing by developing sustainable agricultural prac- tices and environmentally sound packaging; increase the availability of health-promoting foo(ls, such as vegetables, fruits, and whole-grain prod- ucts; and use newer technologies to maintain the low food costs that U.S. consumers have come to expect. Biotechnology that utilizes recombinant DNA or genetic engineering techniques to improve plants, animals, and microorganisms selectively should provide more clesirabie, predictable, controllable, and health-promoting products than conventional crossbreeding technologies. Another area of intense research interest involves modifying foods to help people meet dietary guidelines. Some of these products incorporate newly developed fat and sugar substitutes. Modified foods of the future will contain enhanced or reduced amounts of biologically active components, thereby helping to maximize health and reduce an individual's risk of disease.
29 OPPORTUNITIES IN THE NUTRITION AND FOOD SCIENCES Crosscutting Examples of Our Themes Most of the research recommendations we make in this report illus- trate one or more of the themes described above. In the last section of this chapter, we provide two examples-understanding the functions of vitamin D and combating atherosclerotic heart disease to show the in- terdisciplinary nature of most nutrition and food science research. They are simply two of many examples that could have been chosen. The vita- min D example pertains to an essential substance that is sometimes not obtained in adequate amounts. The heart disease example, in contrast, pertains in part to dietary excesses. Both examples illustrate how research in the basic sciences has led to clinical research, which in turn has driven improvements in the food supply and contributed to the development of food and nutrition policy. Understanding the Functions of vitamin D For centuries, rickets, a disease in which the bones do not have enough calcium and therefore become deformed, was common among urban chil- dren in temperate zones of the world and in young animals raised indoors. Early this century, a substance in animal fat was identified that prevented or cured rickets when given orally. In 1920, this substance was named vitamin D. Soon afterward, it was discovered that sunlight could convert a derivative of cholesterol in the skin to vitamin D. Most people can meet their vitamin D requirements without food as long as their skin is regu- larly exposed to a sufficient amount of sunlight or artificial ultraviolet light. Vitamin D has many functions in the body. The first identified and best known function is that it enables the small intestine to absorb cal- cium and thereby plays a role in the proper formation and maintenance of bones. Vitamin D occurs in abundance in only a few foods, such as eggs, butter, and liver. In 1925, it was demonstrated that certain molecules similar to cholesterol in various foods, including cow's milk, developed vitamin D activity when exposed to ultraviolet radiation. Vitamin D-forti- fied cow's milk, which became available as a result of this basic research, is credited as the major factor in the disappearance of infantile rickets in this country in the second quarter of this century. Using the tools of physical chemistry and engineering, food scientists developed techniques to adcI fat-soluble vitamins to water-based foods. To this day, vitamin D- fortified milk and milk products, margarine, ready-to-eat cereals, and sev- eral other foods are dependable sources of this nutrient and help prevent rickets around the world. Currently, there is renewed research interest in vitamin D because of
INTROD UCTION 23 its relationship to calcium and osteoporosis, a disease in which the bones lose calcium and become weak and subject to fractures. In addition, vita- min D regulates the activities of some genes whose exact purposes in most cases are unknown. The active form of vitamin D in the human body induces the produc- tion of calbindin, a protein that shuttles the calcium released from food in digestion from the small intestine to the bloodstream. Vitamin D also appears to activate a molecule on the intestinal cell membrane that numns 1 · ~.1 · . .- · . .1 1 1 ~. -1~ r ca~c~um from tne Intestine Into the n~ooctstream so that it reaches bone, muscle, and nerve cells where it is needed. Acting with parathyroid hor- mone, vitamin D also mobilizes calcium from the bones, when necessary, so that there is enough of the mineral in the blood for the muscles and nerves to function properly. There are many potential applications for vitamin D and its various forms in clinical care. Patients with chronic kidney failure, for example, have a severely limited ability to convert vitamin D to its active form and therefore often develop a variety of bone diseases. Research is needed to determine how they may benefit from treatment with active forms of vitamin D or synthetic analogues of this nutrient. Children with genetic defects, such as vitamin D-dependency rickets type II, will benefit from work to correct a defect in their cells that prevents vitamin D from being utilized. There is continuing study of the effects of calcium, vitamin D, and estrogen to treat or prevent osteoporosis. Clearly, research to define in detail the exact functions of vitamin D is in its infancy. There is still much to be learned about how vitamin D and the compounds into which the body transforms it regulate calcium ab- sorption from food and the movement of calcium and phosphorus within the various tissues of the body, as well as their roles in preventing and treating osteoporosis and a variety of other diseases. EIow vitamin D and derivatives activate genes associated with growth and development is an- other question that will provide research opportunities with this nutrient. Combating Atherosclerotic Heart Disease Atherosclerosis is a disease process in which arteries that bring nutri- ent- and oxygen-rich blood to the cells of the body become narrowed with intrusive plaques formed by cholesterol and fibromuscular tissue. The coronary arteries of the heart are particularly susceptible to atherosclero- sis, which can begin in childhood and progress silently for decades. When a coronary artery becomes narrowed by atherosclerotic plaque and then becomes obstructed, a heart attack occurs. In the United States each year, more than 1.25 million people (two-thirds of them men) suffer a heart attack; more than 500,000 of them die as a result. The major risk factors
24 OPPORTUNITIES IN THE NUTRITION AND FOOD SCIENCES for heart disease are high concentrations of cholesterol in the blood, high blood pressure, cigarette smoking, obesity, non-insulin-clepenclent cTiabe- tes mellitus, and physical inactivity. Although coronary heart disease (CEID) is the leading cause of death in this country, the age-adjusted death rate from it has dropped substan- tially since 1964. The nutrition and food sciences have helped to reduce the impact of this killer substantially by determining how foods and nutri- ents influence the development of atherosclerosis and by developing clini- cal and population-based strategies to recluce blood cholesterol. Cholesterol and other fat-soluble substances, or lipids, necessary to health are carried in the blood by proteins called lipoproteins. Low-den- sity lipoproteins (LDLs), which carry most of the cholesterol in the blood, are most strongly linked to CHD. As clescribed in Chapter 3, molecular biologists and physiologists have discovered the basic pathways in which the LDLs are formed and function and how the body's production of cholesterol is regulated. Diets high in saturated fat and cholesterol reduce the number of receptors for LDLs in the liver; this, in turn, leads to elevated concentrations of LDLs in the blood. We have learned how cho- lesterol production is regulated at the molecular level and how people differ genetically in their susceptibility to CHD. The work of Michael Brown and Joseph Goldstein in this area was highlighted when they re- ceived the Nobel Prize for Physiology or Medicine in 1985. There are many opportunities to study further the relationship be- tween diet and CHD. For example, antioxidant nutrients such as caro- tenoicis and vitamins E and C may help protect against damage to the artery wall caused by oxiclizecT lipids (unstable fatty molecules that carry extra oxygen). Much work remains to investigate this association and the mechanisms of action. In addition, research is needler! to determine how the body regulates the amount and distribution of its fat tissue, factors that have been linker! to CHD. An increasing number of genetic abnor- realities that may help predict the risk of atherosclerosis is being identi- fied, suggesting that we may soon be able to identify an incTividual's risk of CHD by tests that determine whether or not their cells contain certain "biomarker" genes. Ultimately, people could receive dietary recommenda- tions based on their personal risk of disease. Even though a number of fats in food are linked to CHD, there is no doubt that most people in the United States like fatty foods. Half the calories consumed in industrialized nations come from only two ingredi- ents refined sugar and fat. Fats are responsible for the texture, flavor, and aroma of many foods, enhancing their palatability. The preference for fat in foods may be controlled in part by neurotransmitters, chemicals that enable the cells of the brain to communicate with each other. This is a fertile area for study. It may be possible in the future to design chemicals
INTRODUCTION 25 that will affect neurotransmitters, thereby influencing the amounts and kinds of food people choose to eat. Dietary guidelines have been developed and widely disseminated to make people aware of the links between diet and disease and how to modify their eating habits to reduce the risk of developing these diseases. Many federal and state programs and private sector initiatives have under- taken to teach and apply these guidelines in homes, food assistance pro- grams, cafeterias, supermarkets, schools, and a wide variety of other ven- ues. The National Cholesterol Education Program (NCEP), for example, has helped increase the awareness of both the public and health profes- sionals of the need to reduce cholesterol in the blood. A new, federally mandated food-labeling program that will make it easier for consumers to adopt lower-fat diets will go into effect in 1994. To date, however, most Americans are not meeting dietary guiclelines. Much more research is required to identify the determinants of long-term dietary change and to find the best ways to apply this knowledge to increase healthful eating (anc3 healthful life-styTes generally) in this country. With improved meth- ods of monitoring dietary intake coupled to genetic biomarkers of foot! intake and (lisease risk, surveys could identify subgroups of the population at greatest risk for various diseases. Intervention programs could then be (resigned to help modify those risks. Food technologists are actively involved in mortifying the food supply to enhance health. The food industry is continuing research to produce high-quality, safe, good-tasting, and desirable foods that are Tow in fat, sugar, and salt. Some of the new foods use fat substitutes produced from ingredients like microparticulated proteins, a variety of mollifier! starches and gums, and newly created nonabsorbable fats. By applying advances in biotechnology and animal nutrition, researchers can make the meat of animals raised for food leaner. Gene transfer technology can be used to increase the unsaturated fat and lower the saturated fat content of oil- seeds (such as cotton, sunflower, and safflower). In the future, it will be possible to create "functional" or "designer" foods containing biologically active compounds that may reduce an indiviclual's risk of CHD and other diseases. Making the food supply more healthful will require research to clarify further the biochemistry and genetics of fat, protein, and carbohy- drate metabolism in plants, animals, and microorganisms as well as con- tinued improvements in food production technologies. The aim is to pro- vide people with even more appealing food choices and increase the availability of health-promoting food so they can consume a healthful diet, no matter what their life-styles. -
26 OPPORTUNITIES IN THE NUTRITION AND FOOD SCIENCES CONCLUDING REMARKS Our two crosscutting examples illustrate a pattern in the nutrition and food sciences that often leads to important improvements in public health. First, a clinical condition or problem is clearly identified (e.g., rickets in children and atherosclerotic heart disease). Through research, we gain some, though usually not a complete, understanding of the biological mecha- nisms involved in its genesis, prevention, and treatment. Concurrent ad- vances in food science and technology enable the food supply to be mocli- fied appropriately (e.g., adding vitamin D to foods and modifying the fat content of food products. Finally, government policies are brought to bear on the problem (e.g., mandating vitamin D fortification of milk and establishment of the NCEP>. Chapters 3 through 6 identify many oppor- tunities for research and the development of new and improved technolo- gies in the nutrition and food sciences. By taking advantage of these op- portunities and meeting the challenges they offer, further improvements to public health in the next century are certain. In the next chapter, we provide a brief history of the nutrition and food sciences and more examples of how these disciplines have contrib- uted so importantly to improving our health and well-being.
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