Improving age-segmented dietary guidance – Dietary Guidelines
Lois D. McBean
Age influences both nutrient needs and the risk for developing chronic degenerative diseases. Are the unique needs of children and older adults adequately addressed in the 2000 dietary guidelines for Americans? Is there a need to further segment the guidelines to make them more meaningful and useful to the public? The National Dairy Council sponsored an expert panel to help answer these and other related questions.
Traditionally, dietary guidelines for Americans have been directed at all healthy Americans across a wide age range (ie, from 2 years of age and older). However, age influences both nutrient needs and the risk for developing chronic degenerative diseases. National Dairy Council sponsored a 1-day expert panel, Age-Segmented Dietary Guidance: Improving Our Serve to the Public, to help determine whether the unique needs of children and older adults are adequately addressed in the 2000 Dietary Guidelines (1) and whether separate guidelines for specific age groups would make the guidelines more meaningful and useful to the public.
The panel discussed the history of dietary guidance in the United States and its intended goals. Also addressed were how nutritional needs, intakes, and challenges change throughout the life cycle and how these changes affect food intake. Whether behavioral goals should be part of the guidelines and how psychological/environmental factors uniquely influence the eating behavior of adolescents were considered. In addition, the panel discussed how new information about the unique needs of children and older adults might be incorporated into the Dietary Guidelines and what issues must be addressed in the future. Although the focus was on age-segmented dietary guidance, the panel acknowledged the need to consider the appropriateness of separate guidelines based on gender and ethnicity. Below are some highlights from the expert panel presentations.
History of Dietary Guidance in the United States
David Kritchevsky, PhD, a professor and Caspar Wistar Scholar at the Wistar Institute in Philadelphia, Pa, traced the development of dietary guidance in the United States, such as that issued by the American Heart Association (AHA) and by the US Department of Agriculture/US Department of Health and Human Services (USDA/DDHS) in its Dietary Guildelines for Americans. (1-4)
Clearly, dietary guidance has evolved throughout the years. During the first half of the 20th century, dietary guidance focused on being well nourished to either stave off or recover from infectious disease, which were the major cause of death. However, after World War II, infectious diseases became less of a health threat because of the availability of penicillin and other antibiotics. Chronic degenerative diseases, such as heart diseases, became the major health focus. (2,3) An emerging change us recognition of the unique nutritional needs of children and older afults, with support by numerous health professional organizations for the development of separate dietary guidelines for these age groups. (5) Current dietary guidelines issued by USDA/DHHS (1) and the AHA (4) show some sentivity to the unique nutritional needs of children and older adults. For example, the AHA states: “it should not be assumed that a diet appropriate for adults is also appropriate for children.” (4)
Unique Nutritional Needs of Children and Older Adults
Johanna Dwyer, DSc, RD, Senior Scientist at the Jean Mayer Human Nutrition Research Center on Aging and Professor at the Schools of Medicine and Nutrition Science and Policy at Tufts University, addressed the unique nutritionals needs of children and older adults, the need for research-based evidence to support dietary recommendations, and the pros and cons of age-segmented dietary guidance.
Although children and older adults share many similarities, we know that children are not little adults and that the mental (cognitive), emotional, and physical differences between children and older adults are important. For example, needs for specific nutrients, such as vitamin D, vitamin [B.sub.12], and iron, differ between children and older adults. Compared to children, older adults have a higher vitamin D requirement because of the age-related decrease in skin and kidney conversion to the active form of this vitamin; limited exposure to sunlight, especially for house-bound individuals; and use of sun screens. (6)
The overall goal of dietary guidelines for children differs somewhat from that for older adults. For children, dietary guidance must focus on health promotion and habits fostering later prevention of chronic diseases. In older adults, the focus is on reducing chronic degenerative disease risk and promoting health. Currently, age-specific advice is woven into the current Dietary Guidelines. (1)
The 2000 Dietary Guidelines (1) were developed from evidence-based reviews with expert judgment but without explicit ratings of the quality of the evidence. In Dwyer’s opinion, evidence-based statements in the guidelines will increase and the recommendations will eventually be formally graded. Although children and older adults deserve special attention, we must decide whether age-specific guidelines on the national level are the best way to address these needs. Certainly, more evidence-based research is needed to understand the biologic basis of nutritional differences as we age and in how to communicate them.
Should Adult Fat Guidelines Be Applied to Children?
Paul B. Pencharz, PhD, MD, Professor of Pediatrics and Nutritional Sciences at the University of Toronto, reviewed potential adverse effects of applying adult fat guidelines to children.
Fat intake guidelines for children assume that atherosclerotic plaques start in childhood and that dietary habits imposed in childhood persist into adulthood. However, it is unknown what triggers the change from fatty streaks seen in childhood to later fibrous plaques and whether dietary habits initiated in childhood continue long-term. Furthermore, fat restriction may adversely affect children’s growth and nutrient intakes. (7)
Concerns regarding restriction of dietary fat in childhood led the Joint Working Group of the Canadian Paediatric Society and Health Canada to issue separate dietary recommendations for children. (8) These recommendations advise that from the age of 2 years to the end of linear growth (ie, 16 to 18 years for girls and 18 to 21 years for boys) children should gradually transition from the high fat intake of infancy to adult recommendations of no more than 30% of energy as total fat and 10% as saturated fat. (8) Energy intake should be sufficient to support normal growth and development, and food patterns should emphasize variety and complex carbohydrates and include low-fat foods,a The recommendations also stress the importance of physical activity.
Low fat intake may limit growth, as demonstrated in children with cystic fibrosis (CF) who consumed fat restricted diets (approximately 20%) (9) and in young children (<6 years of age) whose diets provided <22% of energy from fat. (10) Because low nutrient intakes can occur in children consuming low-fat diets under supervised conditions, (11, 12) the risk for inadequate nutrient intakes may be even greater under free-living conditions. Pencharz supports the qualitative Canadian recommendations, which call for a gradual reduction in dietary fat between 2 years of age and the cessation of growth. (8) Normalizing children's energy balance by promoting physical activity may be a safer and an equally effective way of controlling blood lipids than restricting dietary fat.
Addressing Unique Needs of Older Adults in Dietary Guidelines
Ronnie Chernoff, PhD, RD, Associate Director of Education/Evaluation for the Geriatric Research Education and Clinical Center at the John L. McClellan Memorial Veterans Hospital in Little Rock, Ark, discussed older adults’ needs in relation to current Dietary Guidelines.
The purpose of the Dietary Guidelines is primary prevention of chronic degenerative diseases. However, for older adults, secondary prevention strategies may be more appropriate. By the time most people are 55 years old, a chronic degenerative disease, such as hypertension, diabetes, or some early sign of heart disease, likely exists. Compared to younger and middle-aged adults, older adults become increasingly unique in their health status as they age. Because of advances in early detection and treatment of diseases, many older adults remain healthy for many years.
Although specific advice for older adults is included in several of the current guidelines (eg, Be Physically Active Each Day, Let the Pyramid Guide Your Food Choices, and Keep Food Safe To Eat), (1) Chernoff made a case for seriously considering separate dietary guidelines for older adults. For example, body composition changes in older adults support the need for separate guidelines. Weight management at either end of the weight spectrum in older adults is particularly challenging. (13)
Separate dietary guidelines for older adults should include a Food Guide Pyramid tailored to this population. For example, a pyramid for older adults was developed as part of the American Dietetic Association’s Nutrition and Health for Older Americans Campaign. Tufts University has also developed a pyramid for people over 70 years of age. (14) These pyramids for older adults emphasize nutrient-dense foods, fiber, and water/fluids.
Health-promotion programs can help older adults follow dietary guidelines if they are motivated to participate in these programs. (15) To effectively communicate with older adults, messages need to be relevant.
Nutritional Needs for Bone Health Throughout the Life Cycle
Robert P Heaney, MD, the John A. Creighton University Professor and Professor of Medicine, Creighton University, Omaha, Neb, reviewed how nutritional needs for bone health change throughout the life cycle, with an emphasis on calcium, protein, vitamin D, and phosphorus. Considering this information can help to determine whether future issues of the Dietary Guidelines should include a separate guideline for bone health and if this guideline should be targeted to specific age groups.
Bone mass consists of protein, calcium, and phosphorus, all of which must be sufficiently present in the diet to build or sustain bone mass. Calcium is the nutrient that is most likely to be in the shortest supply in modern diets from adolescence onward; therefore, it has received the most attention. (16) However, it is a mistake to believe that providing enough calcium alone guarantees bone health. What changes throughout the life cycle is the need not so much for individual nutrients but for total nutrient intake. For example, adolescence, pregnancy, and lactation are times of increased total nutritional needs and old age is a time when the ability to adapt to poor nutrition declines. Our current nutritional policy defines requirements as the least an individual can get by on without recognized adverse health consequences, rather than intakes that optimize health.
The body possesses adaptive mechanisms that allow it to cope with inadequate nutrient intakes. However, the ability to adapt to low intakes declines with age, which explains why the requirements for many nutrients rise with age. (16) Heaney believes that a minimal adaptive response is ideal. It is not necessarily healthy to be continually exposed to high levels of adaptation. (16) For example, high levels of parathyroid hormone in response to low calcium intake are linked to elevated levels of bone remodeling, a recognized fragility factor. (16)
Protein intake is also important for bones. In the presence of a high calcium intake, the net effect of protein on bone is distinctly positive. (17, 18) When researchers examined age-related bone loss during a 4-year period in a cohort of adults participating in the Framingham Osteoporosis Study, lower total and animal protein intakes were significantly related to bone loss at the femoral and spine sites. (17) The greatest bone loss was observed in subjects in the lowest quartile of protein intake (Figure 1).
[FIGURE 1 OMITTED]
Vitamin D, which enhances calcium absorption, is another nutrient that is important for bone health. (6) Boston researchers reported a high prevalence of vitamin D deficiency among older adults admitted to hospitals, even among those whose vitamin D intakes met expert recommendations. (19) This finding indicates that the current recommendation for vitamin [D.sup.6] may be insufficient for some individuals. Most adults older than 65 years have subnormal vitamin D status, and vitamin D intakes of 1,000 IU/day are needed to keep serum 25(OH)D levels from falling during the winter.
Phosphorus may be problematic for older adults because intake declines with age and many older adults already have low phosphorus intakes. (20) Because calcium supplements aggravate many older adults’ low phosphorus intakes, Heaney recommended calcium-rich foods, such as dairy foods, as the preferred source of calcium. The best and most economic source of the limiting nutrients–calcium, phosphorus, protein, and vitamin D–in older adults’ diets is dairy foods, particularly milk, which is vitamin-D fortified. Consuming dairy foods improves the overall nutritional quality of the diet. (21)
You Want Me to Eat What? I Don’t Think So!
Ellyn Satter, MS, RD, CICSW, BCD, a therapist, author, and lecturer with a private psychotherapy practice in Wisconsin, reviewed food-selection strategies that can positively affect children’s feeding behavior and, ultimately, their nutrition, as well as the importance of considering food selection behavior in dietary guidelines.
Child nutrition must be viewed in the context of relationships or interactions between a parent and child regarding feeding dynamics. (22) Effective feeding involves a division of responsibility between a child and parent/care provider. (23) The parent is responsible for what, when, and where food is offered to a child. The child’s responsibility is to determine how much and whether to eat. Imbedded in this simple principle are important implications in feeding dynamics and children’s development.
Rather than giving people a list of foods and indicating what they should and should not be eating, we need to help people with their food-acceptance skills, explained Satter. The better individuals’ food acceptance skills, the more likely they will be to try new foods, have greater variety in their diets, and receive better nutrition. (24)
If children are coerced to eat a certain food, they will avoid it when they get a chance. Conversely, if children are coerced to eat less food overall or less of a desired food, they will become food preoccupied and prone to overeat when given the opportunity. (25) Pressure decreases food acceptance if these struggles undermine family meals and interfere with parents’ ability to do a good job with feeding. Likewise, catering to children produces poor food acceptance. (26) Overcontrolled and undersupported children accept food poorly Regarding fat, children preferentially choose high-caloric-density food when their energy needs are high. (27) It is important to offer children high-fat, moderate-fat, and low-fat foods; vary the saturation of fat; and let them pick and choose. (27, 28) The important thing is not to restrict children’s fat intake.
Successful child feeding means integrating permission to eat and discipline. Ultimately, the answers to successful child feeding lie with the children, who are wonderful barometers of their own environment.
Psychosocial Correlates of Adolescents’ Eating Behaviors
Dianne Neumark-Sztainer, PhD, MPH, RD, Associate Professor in the Division of Epidemiology, School of Public Health, University of Minnesota, reviewed what adolescents are eating, what factors influence their food choices, and whether dietary guidelines should be modified to better meet their needs.
Data show that a high percentage of adolescents are overweight and many are not eating in accordance with the Healthy People 2010 objectives. (29, 30) For example, only 30% of the girls and 43% of the boys met the target 1,300 mg calcium/day.
To learn what factors adolescents perceive as influencing their food choices and what they view as barriers to healthy eating, Neumark-Sztainer and colleagues interviewed 141 seventh-grade and tenth-grade students in 21 focus groups. (31) The most important factors influencing food choices included hunger/food cravings, the appeal of food (ie, taste/familiarity, appearance, and smell), the time available to them and their parents, and convenience. Secondary factors were availability of food in the home and school, parental influence (eg, eating/cooking behaviors of parents and family meals), perceived benefits (eg, how the food affects health, energy, and looks), and situational factors, such as where they were and whom they were with (eg, at a party or the mall with friends) (31) Mood, body image concerns, habit, cost, media influences, and vegetarian lifestyles were other factors. When teenagers were asked about how to help them eat according to dietary guidelines, they suggested that healthful foods be made to taste and look better, that these foods be the only option, and that healthful foods be more available and convenient.
To learn what factors contribute to low dairy food intake, survey data were collected from 34,710 adolescents in Minnesota. (32) Low socioeconomic status, nonCaucasian race, increased age among girls, low family connectedness, increased body mass index, and weight concerns were associated with inadequate intakes of dairy foods. (32)
In Neumark-Sztainer’s opinion, the usefulness of the current Dietary Guidelines for children and adolescents is fairly limited. Some changes are needed to tie the guidelines to other current guidelines as much as possible. For example, specific guidance for youth about fruit/vegetable and dairy food intake could be incorporated into the guideline, “Let the Pyramid Guide Your Food Choices.”
2000 Dietary Guidelines for Americans: Where Are We Heading?
Rachel K. Johnson, PhD, MPH, RD, Professor of Nutrition, and Dean, College of Agriculture and Life Sciences, The University of Vermont, reviewed the 2000 Dietary Guidelines for Americans (1); the changes made from the previous (1995) edition, including the rationale for the changes; and what kinds of additional research is needed to support the guidelines. For more information about the changes in the Dietary Guidelines, refer to the article by Johnson and Kennedy. (33)
What’s next for the Dietary Guidelines? First, revising the guidelines must be improved by integrating communication expertise into the process. Information gaps in the Dietary Guidelines must be filled. These include basic evidence that adherence to the guidelines benefits health. More information is needed about added sugars, the glycemic index, and the prevalence and severity of lactose maldigestion. Also, the effect of the Dietary Guidelines in promoting improved calcium status among at-risk populations must be determined. Other related questions concern the role of nondairy foods as a source of calcium, the impact of replacing milk with low-nutrient-dense sugarsweetened beverages, and whether children will drink more milk if fewer soft drinks are available. In 1945, Americans drank more than 4 times as much milk as soft drinks. In contrast, by the late 1990s, they were drinking nearly 2.5 more soft drinks than milk (34) (Figure 2). Concern about the displacement of milk by soft drinks is addressed in the current edition of the Dietary Guidelines with the following statement: “Take care not to let soft drinks or other sweets crowd out other foods you need to maintain health, such as low-fat milk or other good sources of calcium.” (1) A recent longitudinal study found that as children’s intake of soft drinks and sugar-sweetened beverages increased, their risk of obesity rose. (35)
[FIGURE 2 OMITTED]
Nutrition monitoring is critical to revisions of the Dietary Guidelines. The 1990 National Nutrition Monitoring and Related Research Act, which recommended revision of the Guidelines every 5 years, if necessary, is no longer in place. Johnson emphasized that dietary intakes and health outcomes must continue to be monitored to ensure up-to-date science-based nutrition policy. For educational tools, there is a need to harmonize the Nutrition Facts label with the Food Guide Pyramid. (36) Currently different serving sizes and different calorie levels are used in the Pyramid and on the Nutrition Facts label. Also, there is a need to revise the Food Guide Pyramid (36) to reflect the Dietary Guidelines. (1)
Conclusions
Some age-specific advice is woven into the 2000 Dietary Guidelines. (1) Children and older adults clearly deserve special attention, but debate continues about whether there should be age-segmented dietary guidelines. The next revision of the guidelines must incorporate new scientific findings yet simplify messages so that they are readily understood and useable. Although the guidelines are based on current scientific data, in many cases, the data are limited. Further, scientists do not always interpret the scientific facts in the same way. In the end, decisions regarding the guidelines must be based on the best expert judgment at the time. Food-selection behavior (eg, the importance of family meals) should be part of the guidelines. With the increased emphasis on decreasing obesity in our population, it is important not to neglect total nutrition. Also, the message that consuming a variety of foods, as opposed to taking nutrient supplements, is the best way to meet nutrient needs must be continually reinforced. Because the science continually changes, the guidelines should be reviewed and, if necessary, revised every 5 years. The guidelines are both a policy document and a consumer document. Age-segmented dietary guidance is more appropriate for the latter.
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Lois D. McBean, MS, RD, Ann Arbor, Mich, is a consultant for National Dairy Council. Judith K. Jarvis, MS, RD, LD, is Director, Nutrition Research and Health Promotion, National Dairy Council, Rosemont, III Corresponding author: Judith K. Jarvis, MS, RD, LD, Director, Nutrition Research and Health Promotion, National Dairy Council, 10255 W. Higgins Rd, Suite 900, Rosemont, IL 60018-5616 (e-mail: judithj@rosedmi.com).
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