September/October 2016

2015–2020 Dietary Guidelines for Americans: Implications for Older Adults
By Qi Hui Wong; Elizabeth Grainger, PhD, RDN; and Steven K. Clinton, MD, PhD
Today's Geriatric Medicine
Vol. 9 No. 5 P. 20

Based on the newly developed 2015–2020 Dietary Guidelines for Americans, experts offer recommendations on dietary patterns designed for optimal nutrition among older adults.

Every five years for the last 35 years, the US Department of Agriculture (USDA) and the National Institutes of Health have chosen a committee of experts to review the scientific evidence regarding diet, nutrition, and health among Americans. This process, referred to as Dietary Guidelines for Americans (DGA), provides a scientific report that serves as a foundation for public health policy and guides regulations that will ensure access to a safe and healthy food supply. Furthermore, the guidelines provide a foundation for healthy aging (See Table 1) and serve as a starting point for those reaching the sixth decade of life and beyond.

In addition to utilizing public health guidelines to orchestrate a healthy dietary pattern, the authors appreciate that aging is associated with a greater risk of many acute and chronic illnesses that require very specific and personalized dietary and nutritional interventions. It is critical that the health care team utilize the expertise of trained experts, registered dietitians (RDs) or registered dietitian nutritionists (RDNs), to assist providers in developing personalized recommendations for common diseases such as diabetes, hypertension, dyslipidemias, and obesity. The following information will highlight some of the key messages of the new DGA 2015–2020 that are particularly relevant to the aging population. In addition, the authors discuss some of the prevalent nutritional deficiencies that practitioners must address in their elder patients.

A Healthy Dietary Pattern
The new DGA emphasizes the importance of orchestrating a dietary pattern that addresses several key principles highlighted in Table 1.1 The foundation of a healthy dietary pattern includes a diverse variety of plant food sources, such as vegetables, fruits, grains (at least one-half of which are whole grains), nuts, and legumes (See Table 2). In parallel, a healthy dietary pattern limits saturated fats, trans fats, sodium, and added sugars. Specifically, Americans are encouraged to consume less than 10% of total calories per day from saturated fats and consume as little trans fat as possible. Sodium consumption should be limited to less than 2,300 mg per day, a standard fewer than 5% of American adults currently meet.2

Finally, a major addition to the 2015–2020 DGA is the recommendation to consume less than 10% of total calories from added sugars each day. This amount is based on the concept that only 10% of discretionary calories remain if an individual is consuming a nutrient-rich healthy diet. Large cross-sectional surveys suggest that American adults consume an average of 73 g of added sugars, nearly 300 calories, each day.3 By 2018, all food manufacturers will be required to list added sugars on food labels' nutrition facts panels. Sugar-sweetened beverages (SSBs) such as soft drinks, juice drinks, sweet tea, and sports beverages are major sources of added sugars in the American diet.4 Although the prevalence of SSB consumption is lower among older adults than younger age groups,4 reducing SSB intake should be encouraged. Additional strategies include decreasing portion sizes of desserts and sweet snacks and choosing unsweetened fruit sauces and yogurts.1

Obesity
Obesity increasingly plagues the aging population and promotes many diseases of aging, impacts mobility, reduces quality of life, and adds to health care expenditures.5,6 Older adults have decreased caloric needs and a reduced metabolism, making them susceptible to weight gain. Thirty-seven percent of adults aged 60 and older are categorized as overweight (body mass index [BMI] of 25–29.9 kg/m2) or obese (BMI ≥30 kg/m2).7 Common chronic diseases of aging promoted by obesity include osteoarthritis, heart disease, diabetes, and many types of cancer.5,6 The causes of the obesity epidemic are multifaceted and involve both complex individual genetic, biologic, and behavioral factors that are impacted by societal changes in lifestyle, the built environment, and the food industry.

However, a basic understanding of obesity is very simple: It is the result of a sustained imbalance where caloric consumption from food and alcohol exceeds caloric expenditure from physical activity and metabolism. Physical activity is encouraged to promote weight loss and increase muscle strength in combination with changes in the dietary pattern, providing a modest but continuous reduction in caloric intake. Dietary patterns that support healthy weight loss include consuming nutrient-dense foods. Nutrient-dense foods include those that are rich sources of vitamins, minerals, and phytochemicals, yet have relatively few calories. Even modest weight loss of 3% to 5% in an overweight individual can produce clinical benefits in health. The DGA notes that there are many dietary patterns, such as Dietary Approaches to Stop Hypertension, the Healthy US-Style Eating Pattern, the Healthy Mediterranean-Style Eating Pattern, and the Healthy Vegetarian Eating Pattern, which can be employed to manage weight. Those needing assistance in defining strategies that are best suited to each individual will benefit from referral to a nutrition professional such as an RD or RDN.8

Clinical Assessment and Treatment
Among the different methods used to identify obesity, calculating BMI (weight in kg/height in m2) remains the most simple. BMI does not differentiate between lean and fat mass but is quick and can be useful in addition to clinical judgment. The most accurate tools to assess body composition are dual-energy X-ray absorptiometry (DEXA), CT, and MRI,9 but these tests are often cost prohibitive and unnecessary.

Sarcopenia
Sarcopenia is the loss of muscle mass, strength, and ultimately a decline in function that accompanies aging, and it may or may not be accompanied by obesity.10 Sarcopenia is estimated to affect 30% of people aged 60 and older and more than 50% of those aged 80 and older.11 Although many factors, including decreased physical activity, account for muscle mass loss in older adults, insufficient dietary protein is an important concern, and considerable evidence indicates that optimal protein intakes combined with regular exercise may help limit age-related sarcopenia.12,13

The Healthy US-Style Eating Pattern of the DGA recommends 5½-ounce equivalents of protein foods per day at the 2,000-calorie level, while the Healthy Mediterranean-Style Eating Pattern and Healthy Vegetarian Eating Pattern recommend 6½- and 3½-ounce equivalents of protein foods per day, respectively.

Some studies have reported potential benefits of higher protein intakes for older adults; however, more research is needed to provide more precise guidance. Presently, it is imperative that the current recommended intake is met with high quality meat or vegetable protein and is coupled with routine exercise to suppress, slow down, or reverse the process of sarcopenia.

Clinical Assessment and Treatment
Clinical assessment of body composition is typically adequate.14,15 Measures of physical function can be combined with clinical assessment and imaging studies. These measures are not routine in most medical clinics but are strongly related to decreased morbidity16 and the risk of falls. Performance-based measures of physical function include a four-meter gait speed test, hand grip strength, and lower extremity muscle power.14 Validated questionnaires (eg, Activities of Daily Living questionnaires)17 and assessing self-reported measures of physical function are additionally useful.18 A review of dietary habits by an RD can help ensure older adults are consuming adequate protein for optimizing muscle mass and physical performance.

Dietary Fiber
Dietary fiber is a term for complex carbohydrates, largely of plant origin, that are not completely digested by human digestive enzymes. Although there are many different types of fiber, they are generally classified into two categories: soluble and insoluble.

Soluble fibers are metabolized by colonic microflora to a much greater extent than insoluble fibers, and many water-soluble fibers have high water-binding capability that produces a viscous solution that slows gastric emptying, allowing for slower digestion and absorption.19 Dietary patterns rich in foods containing viscous soluble fiber are associated with a lower risk of cardiovascular disease because they decrease blood pressure, lower serum cholesterol, and reduce biomarkers of inflammation.20 The fiber that is partially fermented by gut microflora is beneficial for diabetics because these microflora increase satiety and improve insulin sensitivity.21

Additionally, insoluble fibers, along with adequate hydration, are important for reducing constipation, which is often a concern for older adults.21 Most older Americans consume approximately 15 to 17 g of fiber per day,22 an amount lower than the recommended adequate intake of 25 g per day for women and 38 g per day for men (or approximately 14 g/1,000 kcal/day).23

Vegetables and whole grains contribute the largest amount of fiber in the USDA Food Patterns. Fruits also provide a substantial amount of fiber.24 The DGA recommends at least one-half of all grains be consumed as whole grains.

Apart from dietary fiber, whole grains provide other protective health benefits from bioactive compounds found in bran and germ such as vitamins, minerals, and many different phytochemicals.25 Ways to increase whole grains include replacing refined grains with foods such as oatmeal; whole grain ready-to-eat cereals, pasta, and rice; and whole wheat breads, rolls, and bagels.1 Incorporating more vegetables and legumes can also significantly increase dietary fiber intake.1

Clinical Assessment and Treatment
Complaints of persistent constipation may indicate a dietary pattern low in fiber. Dietary fiber assessment is best completed by an RD using a thorough dietary recall. Because there are many different types of dietary fiber, a varied diet replete in fruits, vegetables, and whole grains is ideal, but a fiber supplement can be useful.

Bone Health: Calcium and Vitamin D
Calcium is the most abundant mineral in the body and is critical for healthy bone formation and renewal, nerve transmission, and intracellular signaling.26,27 Vitamin D plays an essential role in optimally regulating calcium homeostasis and can be synthesized in the skin in response to sunlight.28 Vitamin D and calcium work together to maintain the health of bones and other tissues.

Bone health is particularly relevant to aging individuals for whom the risk of osteopenia and osteoporosis is increased, which escalates the risk of hip and spine fractures and ultimately increases the risk of mortality.29,30 More than 53 million people in the United States either have osteoporosis or are at high risk for osteoporosis due to low bone mass.31 In addition, 1.5 million fractures are attributed to osteoporosis each year.32 The risk of bone disease increases with aging due to the decline in the endogenous production of estrogen in women and testosterone in men. Women are especially vulnerable to bone loss, because estrogen deficiency accompanying menopause generally occurs around the age of 50, whereas the decline in testosterone production in men often occurs gradually over later years.27,33

The recommended dietary allowance of calcium for men aged 51 to 70 is 1000 mg/day. For women aged 51to 70 and all adults over the age 70, that recommendation increases to 1,200 mg/day.34 Dietary calcium intake among older adults is frequently lower than the recommendations; the mean calcium intake for adults aged 60 and older is less than 1,000 mg/day.26 Calcium intake is best improved through consumption of dairy products (lower-fat dairy products recommended) or fortified foods.26 Although many vegetables such as kale and broccoli are sources of calcium, the bioavailability of calcium from these foods, compared with dairy products, is poor.35 For those not meeting the recommended calcium intake from foods, supplements are often recommended; however, careful assessment is advisable to ensure that the total combined calcium intake from food and supplements does not exceed the tolerable upper limit of 2,000 mg/day.36

Vitamin D is essential for the host to absorb and metabolize calcium and is increasingly linked to diverse health outcomes related to cognition, immune function, and muscle performance.28 The skin produces vitamin D in response to sunlight; thus, older adults are at a greater risk for deficiency because of their limited sunlight exposure coupled with a reduced dietary intake.37,38 The prevalence of inadequate vitamin D status, as defined by a blood test (25-hydroxy-vitamin D of <20 ng/mL) ) among adults over the age of 60 has been estimated to be between 30% and 50%.39,40 A chronic deficiency reduces bone mineralization28 and may increase fracture risk.34 The recommended dietary allowance of 600 IU/day (serum 25OHD concentration of 15 ng/mL or 37.5 nmol/L) has been established for adults aged 51 to 70 and 800 IU/day (serum 25OHD concentration of 20 ng/mL or 50 nmol/L) for adults over the age of 70.34 The number of vitamin D–rich foods is rather limited (fatty fish, fortified dairy products, and ready-to-eat cereals), so a dietary supplement is reasonable for those at risk of inadequate intake.

Clinical Assessment and Treatment
Circulating 25-hydroxy vitamin D can be used to assess vitamin D status in high-risk individuals. Circulating vitamin D concentration should be at least 50 nmol/L or 20 ng/mL to be considered adequate for bone and overall health in healthy individuals. Bone mineral content and density are measured by DEXA.27 Moderate physical activity (30 minutes per day) and adequate consumption of both calcium and vitamin D from diet and supplements can prevent or slow bone demineralization.41 Antiresorptive medications, such as bisphosphonates, may be considered in some individuals at high risk of fracture. See Table 3 for serum 25OHD concentrations and health status.42

Eye Health: Lutein and Zeaxanthin
Cataracts and age-related macular degeneration (AMD) are two main contributors to vision impairment and blindness with aging.43 According to the 2005–2008 National Health and Nutrition Examination Survey, the prevalence of AMD in the United States was 11.1% in adults aged 60 and older44 and accounted for 54.4% of blindness among white Americans.45 Furthermore, 50% of US adults aged 80 and older have been estimated to have cataracts,46 which are the leading cause of low vision.45

It has long been appreciated that vitamin A plays a key role in eye health and remains a major health issue in developing nations. A growing body of evidence provides a plausible role for the carotenoids lutein and zeaxanthin, which both accumulate in the human lens47,48 and may provide protection by reducing light-initiated oxidative damage.48,49 Adequate intake of antioxidant nutrients vitamin E and vitamin C as well as omega-3 fatty acids are being investigated to improve eye health, but more evidence-based consensus to define optimal intake is required. In general, studies support the role of lutein and zeaxanthin in preventing AMD, though after diagnosis, benefits of carotenoid supplementation studies are less consistent. Rich sources of dietary lutein and zeaxanthin are found in green leafy vegetables such as kale, collard greens, and spinach. Ongoing research will allow expert committees to evaluate the potential benefit lutein and zeaxanthin have on eye health in order to establish possible Dietary Reference Intakes for these carotenoids.

Summary
The 2015–2020 DGA provides recommendations based on current scientific and medical knowledge that aim to promote overall maintenance of good health and prevention of disease. The DGA is designed to focus on foods and dietary patterns that promote health for all individuals aged 2 and older, and it also serves as a basic framework for healthy aging. For aging individuals with specific diet-related concerns, it is advisable to obtain nutrition support from RDNs for a thorough dietary assessment and personalized treatment plan.

— Qi Hui Wong is a student in the division of medical dietetics of the School of Health and Rehabilitation Sciences at the Ohio State University in Columbus.

— Elizabeth Grainger, PhD, RDN, is a nutrition researcher in the Laboratory of Nutrition and Cancer Prevention at the Ohio State University Comprehensive Cancer Center.

— Steven K. Clinton, MD, PhD, is a medical oncologist at the Ohio State University James Cancer Hospital. A program leader in the Ohio State Comprehensive Cancer Center, he served on the 2015–2020 US Dietary Guidelines Advisory Committee.

References
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