This report highlights specific research needs, to aid organizations in prioritizing and distributing research funding. The report comprises three sections, the first of which appears in this issue. The others will be published in future issues.
People have known for thousands of years that specific foods affect certain health conditions, but not until quite recently has science begun to explain why these foods are effective. Although around the 4th century B.C. Hippocrates advocated eating liver as a remedy for night blindness, its active component, vitamin A, was not chemically defined until 1913. Now that science has developed the tools, researchers can unlock the hidden power of food
Scientific advances already have transformed our understanding of nutrition and the role of food in health. At the start of the 20th century, recurring nutritional deficiency diseases, such as rickets, scurvy, beri-beri, and pellagra, were thought to be infectious diseases. In the early 1900s, scientists discovered that food contained essential vitamins and minerals, and that a lack of these substances in the diet caused disease.
Actions taken based on this knowledge have saved hundreds of thousands of lives, if not more. In the United States from 1906 to 1940, approximately 3 million cases and 100,000 deaths were attributed to pellagra. By the end of the 1940s, pellagra had been nearly eliminated by the enrichment of flour with niacin and the improved diet and health brought by economic recovery. Despite our knowledge, nutritional deficiencies remain a serious issue in some portions of the world.
Although identifying and treating nutritional deficiencies was a major achievement, researchers quickly focused their efforts on a new challenge: chronic disease associated with diet. Scientists are rapidly discovering the important role diet plays in prevention and management of chronic diseases, such as cancer, heart disease, obesity, and diabetes. Ironically, the public has enthusiastically embraced some health claims that science has yet to prove, while neglecting others that have been proven for years. For example, the efficacy data for many popular dietary supplements are far less extensive than for traditional nutrient-related claims that are subject to stringent regulatory requirements.
Prevention of chronic disease will draw heavily on genomic research—the study of all the genes of an organism. Genomics helps us understand why disease happens in one person but not another. Coupled with detailed knowledge of the healthful compounds in foods, genomics opens the door to diets tailored for maximum individual health.
The economic return from enhancing our understanding of the impact of food components in preventing and treating chronic diseases is anticipated to be substantial. The U.S. Dept. of Agriculture’s Economic Research Service calculated that the costs for the diet-related portion of four health conditions—coronary heart disease, stroke, diabetes, and cancer—totaled nearly $71 billion each year, after adjustments for double counting (see Table 1). If food and genomics could together prevent or treat more than the agency’s conservative estimates of 30% of cancer and 20% of the other diseases, the potential savings would increase. Of course, the quality-of-life benefits are incalculable.
With funding for research, scientists are poised to fulfill the oft-quoted prophesy made by Hippocrates nearly 2,500 years ago: “Let food be thy medicine, and medicine be thy food.” Food offers great potential to prevent and moderate a host of chronic and genetically regulated diseases, from heart disease and cancer to Alzheimer’s and arthritis. Research funding is needed not only to achieve the potential advances but also to protect us from our enthusiasm by assessing the risks as well as the benefits. We need to unravel the complex interrelationships among the numerous aspects of diet and health.
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Playing Catch Up
Simply identifying the relationship between diet and health is not enough. Consumer understanding of nutrition and health is improving, but corresponding changes in diet do not always follow. For example, educational campaigns have raised the awareness of disease related to under-consumption of nutrients such as iron, calcium, and folic acid. Still, many young women continue to fall short of the recommended intake levels. Social factors, such as the rise in eating away from home, may counteract the education efforts. In addition, people may think their diet contains more nutrients than it does, according to analysis of data from USDA’s Diet and Health Knowledge Survey, which compared people’s perceptions about their diet with the results of a dietary analysis. Before we can capitalize on future scientific advances, we need to find better ways to achieve diet modification.
Obesity is becoming a serious concern. Despite the increased number of “light” or “diet” foods in the marketplace, more Americans are overweight. A reduced-fat food is not always a reduced-calorie food.
American diets are gradually becoming more healthful as the share of calories from fat declines and consumption of fruit and vegetables increases. Still, most Americans are not consuming the recommended number of servings for fruits, vegetables, and whole grains. In addition to basic guidelines, certain populations—such as pregnant women, small children, and the elderly—have different nutritional needs, making it important that we understand these different needs and communicate them clearly.
Awareness of diet–disease relationships is only one of many factors affecting dietary behavior. We must learn why some people adopt healthy eating habits so we can use this knowledge to develop successful intervention and education strategies.
Particular emphasis should be placed on programs for children and adolescents to maximize long-term improvement in the health of Americans. Obstacles to healthy eating habits in elderly and ethnic groups, especially recent immigrant groups, deserve special study because these groups will be an increasing part of the overall population.
Staying Ahead of the Curve
While scientists are still defining terms such as “nutraceutical” and “functional food,” consumers have enthusiastically embraced claims about the health effects of substances in functional foods and dietary supplements. Although disease-related claims are tightly regulated, other more general claims are not as limited. Additional research is needed to obtain the maximum health benefits for consumers while protecting them from inaccurate claims and potentially dangerous levels of consumption.
Fig. 1 lists the dietary health claims for foods that are currently allowed under the Food and Drug Administration’s nutrition labeling regulations. Although some of these health claims are based on individual nutrients, others address whole foods and are dependent on the fat, saturated fat, and cholesterol content of the foods. Some claims are lifestyle impacting, i.e., if the fiber, grain, fruit and vegetable content of the diet were increased, there could be a reduced risk of some cancers. In these cases, it is not known if the reduced rates of disease are due to the presence or absence of a single dietary ingredient or to the combined effect of many. Like Hippocrates so many years ago, we can observe the effect with out completely understanding the mechanism. With adequate resources, scientific research will soon advance our knowledge far beyond our current understanding.
Researchers need to investigate the food components not traditionally considered essential nutrients that produce biological effects on the human body. These substances may have a positive or negative impact on general health and the development of chronic disease. The bioactive “functional” food components currently under study number in the hundreds and include such compounds as phenolics, lipids, isoflavones, omega-3 fatty acids, and carotenoids. In addition to enhancing overall health, potential benefits cover chronic diseases such as agerelated eyesight decline, coronary heart disease, colon cancer, and impairment of immune system function.
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To study the effect of these food components on the body, scientists need biomarkers that can be used to study bioactive substances in foods and quantify their intake, absorption, and effect. A biomarker is a measurable parameter in a living organism with a direct relationship to the disease being studied that can be used to indicate and/or quantify the effect of a substance on the body. For example, insulin and blood glucose levels may be measured to determine the effect of a food substance on insulin resistance, a condition where the tissues of the body have a reduced sensitivity to the action of insulin. With all other parameters controlled, researchers can use the relationship between insulin and blood glucose levels as a biomarker; when different amounts of the study substance are consumed, the change in the insulin levels compared to blood glucose levels provides quantitative data about the magnitude of the substance’s effect.
For a more thorough understanding of the benefits and risks of foods, researchers must study the bioactivity of the wide range of food components and whole foods. Scientists need to understand how the absorption and action of these substances changes for different foods and individuals. The interactions between compounds and the impact of various combinations on uptake, bioactivity, and effect also must be considered for both whole foods and dietary supplements. To complete the picture, scientists must find the site or sites of action within the body that trigger the health effect and determine the impact of various delivery methods on the effectiveness of the substance.
Safety must be a critical issue in efforts to improve health through diet. For many of these foods, positive health effects must be balanced against any negative effects on vulnerable segments of society. The optimal levels of the majority of bioactive components have yet to be determined. Additional research is needed to establish an upper safe intake level for specific compounds and also for foods that contain substances with both positive and negative effects. For example, some phytochemicals (bioactive components of foods of plant origin) such as allyl isothiocyanate that have demonstrated cancer-preventing properties also have been shown to be carcinogenic at high concentrations.
Although we devote substantial effort to reducing the presence of pathogenic microorganisms in food, the presence of certain microorganisms is desirable. For example, food systems can deliver live microbes, known as probiotics, that have a positive effect on human health, usually through microbiological activity in the gastrointestinal tract. In addition, a variety of non-digestible oligosaccharides, fructans, and other carbohydrates—known as prebiotics—may play a role in increasing bifidobacteria or other “beneficial” bacteria in the colon. Additional information will enable scientists to harness the positive effects of probiotics (such as decreasing heart disease and colon cancer), increasing the absorption of minerals (such as calcium for prevention of osteoporosis), and decreasing the absorption of dietary fats.
Building the Future
Many chronic diseases are caused by human genes whose function changes as people live longer. Some of these genes produce more of a material than they once did, while others may produce less. Now that scientists have described the entire human genome, we can begin to identify the key genes, metabolic pathways, and proteins that are involved in individual responses to food components. Understanding the genomes of food plants and animals will reveal why certain foods cause an allergic response in some people and why certain foods seem to be involved in chronic disease in some, but not all, individuals.
Rapid progress toward learning the role of each human gene and the relationship of the gene’s action to health and well-being will open the door to innovative new treatments for chronic disease.
Substances found in foods can regulate the action of specific genes. Reducing the amount of human gene product(s) via specific foods may prevent the onset of some chronic diseases, while increasing the amount of other gene product(s) may prevent the onset of other chronic diseases.
This information, combined with our understanding of bioactive food components and consumer food-selection behavior, will enable scientists to provide tailored diets that promote the health of individuals with unique needs. Moving further ahead, then, these tailored diets will require a whole new public education effort, building on the successful strategies already developed.
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Research Priorities
The role of food in health is poised for dramatic change that must be based on a strong scientific knowledge base. Research into the following priority areas will enhance the health of people now and in the future. Specifically, research should:
• Identify why some people adopt healthy eating habits and others do not. Develop effective ways to encourage increased consumption of health-promoting foods and to discourage excess consumption of foods linked to chronic diseases. Find ways to better address the different dietary needs of specific populations.
• Develop biomarkers that can be used to study the effect of food substances on the human body. Identify the presence of substances in various foods; quantify the intake, absorption and effect of these substances; and catalog the presence and activity of specific genes.
• Determine the positive and negative biological effects of the various bioactive food components in whole foods, functional foods, and dietary supplements throughout the human life cycle.
• Identify the effects of dietary components, including prebiotics and probiotics, on the gastrointestinal tract and the resultant impact on health.
• Find the safe upper limit for consumption of specific food components and whole foods.
• Find food substances that modulate the production levels of genes that affect overall health or cause chronic disease, and design delivery systems to enable the substance to reach its site of action.
• Create health-enhancing foods by using traditional and genomic methods.
The Diet and Health section of the IFT Research Needs Report was prepared by the following committee:
Mary Ellen Camire, University of Maine (Chair) Lynne Margaret Ausman, Tufts University Eric Decker, University of Massachusetts Duane Larick, North Carolina State University S. Suzanne Nielsen, Purdue University Ruth Patrick, Louisiana State University & Pennington Biomedical Research Center Devin Peterson, University of Minnesota Joe Regenstein, Cornell University Daryl Schaller, Consultant, Schaller Consulting Myron Solberg, Rutgers University Richard Whiting, Food and Drug Administration Stacey Zawel, Grocery Manufacturers of America