Many theories exist to explain why chronic diseases typically increase across the life span. Traditional theories for the adult development of chronic disease suggest that diseases emerge due to wear and tear on the body, declines in metabolic efficiency, or sedentary lifestyles that normatively accompany advancing age. The explanatory power of traditional age-related disease theories are increasingly threatened by the rising numbers of obese young people who have developed chronic disease. Chronic disease rates continue to be higher in those over the age of 65, but rates are climbing in young adults due to the high rates of childhood obesity (CDC, 2016). Type 2 diabetes, dyslipidemia, and atherosclerosis were historically adult onset diseases but with childhood obesity, they are increasingly identified in children and adolescents.
While researchers continue to fine tune their understanding of nutrient functions, they also investigate the impact of inadequate and excessive nutrient intakes on chronic disease risk. Excessive intakes of energy yielding nutrients encourage adipose tissue storage, and high levels of adipose tissue in the body can increase the risk of obesity, heart disease, diabetes, sleep apnea, stroke, osteoarthritis, some types of cancer, gallbladder disease, and poor mental health (CDC, 2015). Excessive macronutrient intake is not the only cause of obesity and high body fat mass. Lack of physical activity, hormone imbalances, certain diseases, drugs, genetics, and our built environment may also cause obesity (CDC, 2015). Nearly 35% of adults living in the United States are obese (CDC, 2015). Among those aged 65 and older, nearly 24% are obese (CDC, 2013). Obesity is defined as having a body weight higher then what is considered to be healthy based on the individual’s height. Obesity is typically measured by body mass
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index (BMI) which is an equation that factors in the individual’s height and weight. A
BMI over 30, for adults, is considered obese.
The health status of older adults has become a focus of many health agencies. Due to aging baby boomers and longer life spans, the populations of those over 65 years old is expected to double in the near future. According to the Centers for Disease Control and Prevention (2013), 20% of the population in 2030 will be over the age of 65. In the early 1900’s the life expectancy for men and women was in the late 40’s (CDC, 2014).
Now, the life expectancy for adults living in the United States is over 78 years for men and women (CDC, 2014). The causes of death have changed significantly as well. In the early part of the twentieth century the leading causes of death for adults was infectious disease. Now, the top leading causes of death for adults over the age of 44 are heart disease and cancer (CDC, 2015). Older adults are more likely to have at least one chronic health condition, and treatment of comorbidities among seniors will account for nearly 66% of the country’s healthcare budget (CDC, 2013).
With the growing number of older adults and the increased incidence of chronic disease due to obesity the government is shifting its focus from disease management to disease prevention and health promotion. As a result, diet and exercise are at the forefront of federal, state, and community agendas and programs. This requires all agencies to improve their understanding of food choice and behavior.
Six Classes of Nutrients
Nutrition is defined as the “act or process of nourishing or being nourished…and the science or study of the nourishment of human…” (Turley & Thompson, 2013).
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minerals, and water. To survive and grow we need adequate amounts of these six
nutrients. Carbohydrates, lipids, and proteins are considered macronutrients because they provide energy for our body. Vitamins, minerals, and water are micronutrients, which serve to sustain necessary chemical processes in the body. Our needs for these six nutrients are met by food, which basically represents anything we eat that contains these nutrients.
Carbohydrates are essential for providing our body with energy and sparing the denaturation of proteins for energy. Carbohydrates are the primary source of fuel for the body and are readily available in the diet and relatively easy to consume. Carbohydrates can be found in fruits, vegetables, dairy foods, legumes, cereals, and grain products. In the United States, our intake of carbohydrates is higher than any other macronutrient due to the wide variety of carbohydrate sources (Austin, Ogden, & Hill, 2011). Carbohydrate food sources have been available, historically, in the American diet despite food
shortages and fad diets. The minimum recommended intake of carbohydrates in the diet is around 130 grams per day, with a goal of 45%-65% of daily total calories coming from carbohydrates (USDHHS, 2015).
Protein is made up of amino acids, twenty of which are recognized by the body. These amino acids serve as building blocks for all working and structural molecules, including components of many organ systems in the body. Amino acids are found in a wide variety of foods including animal products, dairy, whole grains, nuts and seeds, and vegetables. The highest sources of protein consumed in the United States are found in poultry, red meat, milk, and cured meats (Phillips et al., 2015). Current
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which equates to about 8 grams of protein for every 20 pounds of body weight (Institute of Medicine, 2005). According to the Dietary Reference Intakes (2005), 10%-35% of daily total calorie intake should come from protein. Protein intake is modified based on activity level and the presence of certain diseases. Over the past 50 years, the
consumption of protein foods, including meat, eggs, and nuts, has increased in the United States (USDA, 2015).
Lipids, also known as fats, are the most calorie dense of all the macronutrients. Fat includes three major classes: triglycerides, phospholipids, and sterols, with the majority of fat in our diet coming from triglycerides. There are multiple functions of fat in the body, including cushioning, thermoregulation, and long-term energy storage. Fat is naturally found in animal products, dairy, nuts and seeds, and some vegetables. It is also consumed when added during food preparation as a means of enhancing flavor and texture. The daily recommendation for fat intake has changed considerably over the years and more focus has been given recently to reducing the consumption of ‘bad’ fats
(USDHHS, 2015). Daily consumption of total fats should be limited to between 25%- 35% of total calories. Fats are encouraged to be consumed in low amounts due to their high calorie content and risk for poor health (USDHHS, 2015). However, lipids are essential and cannot be avoided entirely.
In the case of vitamins and minerals, there are still many details we don’t know
about safety and efficacy. Vitamins and minerals are found in a wide variety of foods including fruits, vegetables, meats, nuts, whole grains, and dairy. Fruits and vegetables are nutrient dense foods because they are rich in carbohydrates, vitamins, minerals, and fiber while also being low in total calories. Low fruit and vegetable consumption may
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result in many vitamin and mineral deficiencies, which could lead to dysfunctions in metabolism, poor cellular growth, decreased bone mineral density, fluid imbalance, impaired muscle contraction, anemia, and a depressed immune system. Daily
recommendations for vitamins and minerals are established by the Dietary Reference Intakes and vary based on age and sex. Studies of many vitamins and minerals lack sufficient scientific evidence to provide daily recommendations and will only offer Tolerable Upper Limits1. Many vitamins and minerals, consumed in excess, can produce toxic effects in the body. For example, it is understood that excessive intakes of Vitamin E can increase the risk of prostate cancer (NCI, 2015).
Food Intake Studies
Humans have always required food to maintain life and good health. But there is more to food than just nutrition and more recently the shift has been eating for enjoyment rather than survival. Humans have adapted their eating behaviors based on multiple factors. Food intake, expressed in behavioral terms, involves a complex interaction between biological, psychological, social, cultural, and environmental elements. These five groups of elements influence the nearly 200 food-related decisions made each day (Wansink & Sobal, 2007). The degree to which these influences elicit a specific food behavior is unknown. Multiple research studies have investigated food intake patterns and behaviors. Most studies collect the ages of participants to report generalizations about age groups, but do not explore period or cohort affects. Furthermore, the majority of studies lump all older adults into one category generally defined as over the age of 60.
1 Tolerable Upper Limits are the highest intake levels recommended for individuals of different ages and genders that likely pose no health risk.
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Prospective and longitudinal data collection efforts have tracked specific nutrient and food intake patterns of individuals in the United States. The Center for Disease Control and Prevention funds two noteworthy studies; the National Health and Nutrition Examination Survey (NHANES) and the Behavioral Risk Factor Surveillance System (BRFSS). Despite the fact that NHANES and BRFSS have been surveying the American population for over thirty years, neither follows the same individuals throughout
subsequent years. Current trends from NHANES data indicate that intake of energy- dense, nutrient-poor foods has increased (Block, 2004) and intake of healthy foods like fruit and vegetables falls below the recommended levels (Casagrande, Wang, Anderson, & Gary, 2007). Energy-dense, nutrient-poor foods are those that provide a large amount of calories without the added benefit of nutrient variety. Block (2004) identified sweets and desserts, alcoholic beverages, and soft drinks as specific nutrient-poor foods
consumed in high amounts among Americans.
BRFSS trends support NHANES findings but, due to the nature of the telephone survey, only data on fruit and vegetable consumption are collected. The benefit to consuming high levels of fruits and vegetables moves beyond nutrient-density to the presence of phytochemicals that are beneficial for health. The BRFSS targets fruits and vegetables due to their ability to reduce the risk of chronic disease and help individuals maintain healthy body weight (BRFSS, 2014). BRFSS data collected between the early 1990’s and 2000’s indicate that adults over the age of 65 were more likely to meet
recommended fruit and vegetable intake (Blanck, Gillespie, Kimmons, Seymour, & Serdula, 2008; Li et al., 2000). The intake of fruit and vegetables among older adults,
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while still higher than other groups, is starting to decline according to BRFSS (Serdula et al., 2004).
The National Food Consumption Survey (NFCS) and the Continuous Survey of Food Intake by Individuals (CSFII), sponsored by the United States Department of Agriculture (USDA), have also attempted to study food trends. These studies began in the early 1980’s and were repeated ten years later. The same participants were not
surveyed at both points in time, and neither study was continued after 1998. The surveys collected food intake via 24-hour recall and a food behavior questionnaire. Results indicated that total calorie and macronutrient intake levels were highest among adults aged 20-39 (USDA, 1997). Consumption trends of some foods varied among age groups. For example, adults over the age of 60 reported less change in their consumption of calorie-rich beverages compared to younger adults (Nielsen & Popkin, 2004). Differences in food intake among sex and ethnic groups were also presented by the USDA surveys. Women, as a whole, had stable fruit and vegetable intake patterns during the two survey periods (USDA, 1997). Black women had the lowest milk intake among ethnic groups while Hispanic women had higher dairy food intake (Siega-Riz & Popkin, 2001).
A small number of longitudinal studies have followed the same group of people over time, adding to the pool of information related to life span trends. The Framingham Heart Study, the Nurses’ Health Study, and the Coronary Artery Risk Development in
Young Adults (CARDIA) study include assessments of food intake and physical activity levels. All three of these research efforts include data examining the relationship
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time those data sets allow researchers to identify the development of chronic disease in relation to physical activity, food intake, and other health behaviors. Participants are recruited in limited regions of the United States and sample sizes are smaller than the previously mentioned government funded surveys.
The Framingham Heart Study was initiated in 1948 under the direction of the National Heart Institute. Little was known about heart disease and its risk factors in the 1940’s, but death rates due to cardiovascular disease were climbing (Framingham, 2016).
Approximately 5,000 men and women living in Framingham, Massachusetts were
recruited for this study. These participants returned every two years for follow-up exams and questionnaires. In 1971, the study recruited a new class of participants from the children of the original cohort. The grandchildren of the initial cohort were also recruited in 2002. Despite the inclusion of multiple birth cohorts, data have not been used for cross-cohort studies. Results from the Framingham Heart study have provided groundbreaking evidence about the risk factors for cardiovascular disease. Two risk factors identified include physical inactivity and obesity (Framingham, 2016). Food trends reported by the Framingham Heart Study indicate that intakes of total
carbohydrates have decreased over time, but intakes of total fat, sodium, and alcohol have increased (Makarem, Scott, Quatromoni, Jacques, & Parekh, 2014).
The Nurses’ Health Study began in 1976 with funding from the National Institutes for Health, with a primary focus being on women’s health and the impact of oral
contraceptives (NHS, 2013). The Nurses’ Health Study went through two revisions, in
1989 and 2010, to include larger samples of nurses and identify more women’s health issues. Each cohort completed follow-up questionnaires every two years. Several
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reported findings related to diet and health. Based on the results of the Nurses’ Health Study, high intakes of red meat increase the risk of developing colon and breast cancer (NHS, 2013). Results also suggest that high intakes of various vitamins and minerals may decrease the risk of developing colon cancer, pathological cognitive decline, and eye disease (NHS, 2013). High intakes of fruits and vegetables in non-obese young women lead to healthier weight status across the life span (He et al., 2004).
The CARDIA study, sponsored by the National Heart, Lung, and Blood Institute, began in the 1980’s with a group of 5,000 men and women aged 18-30 years (CARDIA,
2016). These participants completed a questionnaire every two years. The most recent follow-up of these initial participants and their health status was conducted in 2010-2011. The primary focus of this study was to identify risk factors in the development of heart disease. Physical activity, diet, and other lifestyle factors were collected from each participant throughout the years. Despite its focus on heart disease, the CARDIA study also discovered the relationship between diet and physical activity in the risk for
developing diabetes, nonalcoholic fatty liver, inflammation, and hypertension (CARDIA, 2016). CARDIA results highlight the food environment as being a major factor in diet quality and adherence to fruit and vegetable intake (Boone-Heinonen et al., 2011). Another major finding based on CARDIA results was that maintaining a healthy lifestyle in young adulthood would promote better cardiovascular health into middle adulthood (Liu et al., 2012).
Another study aimed at exploring the relationship between nutrition and health over chronological time is the NuAge study. This recently established longitudinal study is conducted in Quebec, Canada, and is limited to residents of that area. The NuAge
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study began in 2003 and continues to be funded by the Canadian Institutes of Health Research in Quebec, Canada. 900 men and 900 women born between 1921 and 1935 are followed every five years. The results of the initial five year assessment highlights the importance of adequate nutrition in older adults despite changes in health status and quality of life (Vesnaver, Keller, Payette, & Shatenstein, 2012). As with other longitudinal studies, NuAge is limited in the span of ages and quantity of participant enrollment. In addition, no cross-cohort or time sequential analysis is conducted.
The Five Dimensions of Food Intake
Most disciplines agree that nutrition impacts health. Research studies are often focused on a single factor contributing to the behavior; however, there are multiple factors working simultaneously. The five factors most commonly highlighted by food choice and behavior researchers fall within social, cultural, environmental, physiological, and psychological dimensions.
Social Factors. Individuals live and interact with others within a socioecological
sphere. Within an interpersonal level, individuals interact with family members, close friends, and peers. These interpersonal relationships exist within a network or
community that exhibits influence on the behavior of the individual (Bronfenbrenner, 1974; McLeroy, Bibeau, Steckler, & Glanz, 1988). Depending on where this network or community is located geographically, the influence on food intake may vary
considerably, and factors that influence one socioecological level will impact all other levels. Individuals are influenced by their network or group, social modeling, and social norms.
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Interpersonal spheres of influence will impact food intake throughout the life span. The emerging social network can be a time and age sensitive barrier or motivator of food intake. The food relationships within the social network are ever-changing constructs that are rooted in social or commensal eating. Commensal eating primarily considers a family meal but also includes meals eaten with friends of neighbors. Commensal eating episodes could be a family meal at Thanksgiving or a neighborhood picnic on the Fourth of July. Social eating2, like commensal eating, can create kinship and friendship patterns (Sobal & Nelson, 2003). Often foods prepared and presented for commensal eating episodes are shared among individuals. These shared foods encourage social interaction and a sense of belonging (Kauppinen-Raisanen, Gummerus, & Lehtola, 2013).
Food is often important at times of feasting, or even commensal and social eating, to help shape and control social behavior (Mennell, Murcott, & Vanotterloo, 1992). Social behavior may also be mediated by family roles and norms. For example, one family member’s role at the Thanksgiving meal may be to carve the turkey whereas other members assume standing roles of providing certain ‘traditional’ items ranging from
gravy to elaborate casseroles. Social norms are also expressed by the seating
arrangement of members during the meal (Russell, Firestone, & Baron, 1980; Schrieff, Tredoux, Finchilescu, & Dixon, 2010) or in the quantity of food ordered at a restaurant (Cavazza, Graziani, & Guidetti, 2011). Participation in commensal eating is not consistent across the life span. Changing family dynamics as children move towards adolescence can have profound impacts on the frequency and meanings of commensal
2 Social eating episodes occur when a group of individuals eat together while following specific social norms and eating patterns (Douglas, 1972; Douglas, 1984).
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eating. For example, older adults often prefer to eat with immediate family members in their home rather than outside their homes with friends (Sobal & Nelson, 2003).
Social modeling is also a way that interpersonal relationships can influence food intake. Social modeling creates a desire in the individual to mimic the eating patterns of those within their social network (Stroebele & De Castro, 2004). Social modeling has been widely researched in children, adolescents, and younger adults as a contributor for food choices. Within these age groups, peers, friends, and parents are all models of eating behaviors (Harris & Ramsey, 2015; Hermans, Herman, Larsen, & Engels, 2009; Houldcroft, Haycraft, & Farrow, 2014; Loth, MacLehose, Larson, Berge, & Neumark-