How Dietary Needs Change with Aging

Dietary needs change with aging in several ways:

• People become less active, their metabolism slows, their energy requirement decreases, all of which mean that they need to eat less.
• Recent research demonstrates that because older adults’ abilities to absorb and utilize many nutrients become less efficient, their nutrient requirements (particularly as a function of body mass) actually increase. Tucker mentioned that the last set of nutrition recommendations issued by the Institute of Medicine (IOM) include separate recommendations for people age 70 and above for this reason (IOM, 2006).
• Tucker noted that as some of the previous speakers had discussed, chronic conditions and medications can affect nutrition requirements. For example, in addition to drug-nutrient interactions affecting drug metabolism, some drug-nutrient interactions are also nutrient wasting. This is especially true of the B vitamins.

Maintaining a nutrient-dense diet is critically important for older adults because of the impact of food intake on health. Years of research have demonstrated that diet quality has a huge effect on physical condition, cognitive condition, bone health, eye health, vascular function, and the immune system. Yet, this can be challenging to achieve for several reasons:

• As Pelchat discussed, aging is often accompanied by a loss of appetite and changes in taste and smell, all of which can lead to more limited food choices and lower intake of healthful foods.
• As Jensen discussed, aging is also often accompanied by general oral health decline and a reduced ability to swallow, which can affect food choice and intake.
• Many older adults experience mobility constraints, which make it difficult to shop for food, lift heavy jars, open containers, etc.
• As both Wellman and Kinsella mentioned, low income is prevalent in aging populations, making it difficult for many older adults to access high quality foods (i.e., because those foods tend to be more expensive).

A Modified Food Guide Pyramid for Older Adults

Because of the changing dietary needs of older adults, Tucker’s colleagues at the Jean Meyer USDA HRNCA developed what they termed the Modified Food Pyramid for older adults (Russell et al., 1999) (Figure 5-1). Key modifications to the original USDA Food Guide Pyramid include placement of water at the bottom of the pyramid because many older adults do not drink enough water to stay hydrated, and placement of a flag at the top of the pyramid indicating the need for calcium, vitamin D, and vitamin B₁₂ supplements because many older adults do not get enough of these nutrients in a standard diet. After an update to the Food Guide Pyramid took place for the general population, Tucker’s colleagues also created a new Modified MyPyramid for older adults with illustrated examples of healthful foods in each food group (Lichtenstein et al., 2008) (Figure 5-2). Key modifications to the original MyPyramid include the addition of examples of physical activity at the bottom of the pyramid. Greater physical activity allows for intake of larger quantities of food, which in turn increases the likelihood that all of the necessary nutrients will be consumed. Also, physical activity helps maintain muscle mass with aging.

FIGURE 5-1

The original Food Guide Pyramid and the modified Food Guide Pyramid for adults more than 70 years of age. SOURCE: Russell et al., 1999.

FIGURE 5-2

A modified MyPyramid for adults more than 70 years of age. SOURCE: Lichtenstein et al., 2008.

Dietary Patterns of Older Adults

Of course, not all older adults follow the guidelines of the modified MyPyramid. Tucker discussed the variety of ways that older adults eat. She and her colleagues have been examining dietary patterns in older adults as part of the Baltimore Longitudinal Study on Aging.¹ They identified five eating patterns: “white bread” (people that obtain considerably more energy intake from white bread [16 percent, on average] relative to other patterns), “healthy” (higher energy intake from fruit, high fiber cereal, and whole grain bread), “meat” (higher energy intake from meat and potatoes), “alcohol” (higher energy intake from alcohol), and “sweets” (higher energy intake from baked sweets) (Newby et al., 2003). As just one example of how diet affects health, she showed data on waist circumference. Generally, as people age, their weight increases with the rate of increase slowing down over time; most of the gained weight is deposited in the central area of the body. Tucker and her colleagues found that older adults in the “white bread” group experienced a significantly greater increase in weight circumference than older adults in the other eating groups. The “healthy” group showed the least gain in weight circumference.

Dietary Variety

In conclusion, Tucker said that “one of the most important things we can do for the aging population” is ensure good dietary intake. Important risk nutrients include protein; omega-3 fatty acids; dietary fiber; vitamins B₆, B₁₂, and E; calcium; magnesium; and potassium. Many older adults are not getting enough of these nutrients. On the other hand, too many older adults are getting too much folate and sodium. She remarked the best way to ensure good dietary intake is by increasing intake of whole grains, fruits and vegetables, fish, nuts, lean protein sources, and low-fat dairy and decreasing intake of refined grains and highly processed foods. Tucker emphasized the importance of complexity in the diet and referred to a study suggesting higher dietary variety is associated with overall better nutritional status and better health outcomes in frail elderly people (Bernstein et al., 2002). The challenge is getting good quality foods to this population.

What Is a Functional Food?

Barnes explained that functional foods were not specifically defined in the Federal Food, Drug, and Cosmetic (FDC) Act of 1938. Instead, he referred to a 1994 IOM definition of functional food: a “food or food ingredient that may provide a health benefit beyond the traditional nutrients it contains” (IOM, 1994). Many functional foods are conventional foods, that is, foods that were foods even before the concept of a functional food was generated; often they contain specific GRAS (Generally Recognized as Safe) components with known benefits. However, anytime a health-promoting claim is made about an item that is not related to the item’s “nutritive” value, the item is considered a supplement and thereby falls under the provisions of the Dietary Supplement Health and Education Act (DSHEA). If a claim is made that relates to disease treatment or prevention, the item is considered a drug.

Barnes’s interest in functional foods stemmed from his interest in soy and the fact that the chemistry of isoflavones varies among different types of soy foods. In Asia, soy is consumed largely in the form of miso, which is a fermented form of soybean; and soymilk and tofu, which are extracted from heated soybean. In the United States, on the other hand, soy is consumed largely in the form of textured vegetable protein, which is processed differently than the common Asian soy foods and therefore has a different composition (i.e., it is processed through dry heat, not fermentation or hot water extraction). In fermented and hot water extracted products, the soy isoflavones are not only converted into readily absorbable forms of genistein (i.e., 6-hydroxy and 8-hydroxy genistein), they also contain added chemical groups that make them more bioactive. With dry heat, on the other hand, the isoflavones are converted into an acetyl glucoside form of genistein that is not absorbed very well until it reaches the lower gut. Barnes questioned whether the benefits of fermented or hot water extracted soy functional foods exist with these other dry heat products.

In addition to isoflavonoids in soy (and also kudzu), some of the other most common bioactive components of functional foods include fiber (in whole grains), carotenoids (in carrots, tomatoes and green vegetables), allicin (in garlic), flavonoids (in fruits and green tea), sulforaphane (in broccoli sprouts), and omega-3 fatty acids (in wild fish).

Functional Foods for Aging Populations

Barnes stated that these and other bioactive compounds could be used to create functional foods for older adults that improve or maintain taste and smell, digestion, brain health, the immune system, bone and joint health, cardiovascular health, gut flora (i.e., probiotic foods), and eye health. A recent survey indicates that many older adults are in fact eating more fruits and vegetables as they age because of these and other potential health-promoting (i.e., functional) benefits (Shatenstein et al., 2003). As for dietary supplements, the top 20 sellers in 2008 are listed in Table 5-1.

TABLE 5-1

Top-Selling Dietary Supplements in 2008.

Barnes emphasized the importance of considering whether foods are in a form that older adults can actually digest. Not only do many older adults not have adequate teeth, they could be experiencing problems related to impaired acid production (e.g., due to medications that interfere with acid production), or other physiological changes such as those discussed in Chapter 3.

Bioavailability: Absorption, Distribution, Metabolism, and Excretion (ADME) in Older Adults

Barnes recalled how once, as a student, he had entered a pub late in the evening and observed a group of “little old ladies” knitting and drinking stout. He realized later that the women were probably not drinking the stout to drink stout, but rather because stout is very nutritious for older adults. A pint of stout has only 200 calories, is low in sodium, and is rich in vitamin B₆, iron, and flavonoids. He described stout as a “very good soup.” Moreover, it is easy to digest. Stout is a great example of how physical form matters. He stated that foods are generally much better than dietary supplements in terms of bioavailability, because the bioactives are generally much more dispersed among the food particles and therefore more likely to be absorbed by the body. Bioavailability of purified compounds (i.e., a dietary supplement) is very dependent on the physical properties of those compounds, and many dietary supplements are simply not very well absorbed.

He used flavonoids in foods to illustrate how bioavailability is impacted by the physiology of the gastrointestinal (GI) tract, beginning in the oral cavity where pre-hydrolysis (i.e., pre-digestion) dissolves some fats and sends signals to the rest of the GI system that “food is coming.” Then, in the stomach, there may be some hydrolysis, although Barnes is unsure to what extent. Small intestine metabolism, however, is definitely very important, with lactase and other intestinal enzymes preparing (hydrolyzing) the flavonoid glycosides⁷ for enterohepatic circulation (i.e., the compound passes through either the small intestine or large intestine wall, enters the liver where other metabolic processes occur, and then reenters the small intestine). Flavonoids not absorbed in the small intestine are metabolized by microflora in the colon, where they undergo considerable structural modifications. In the colon, bioavailability is impacted by transit time and bacterial composition, with a faster transit time leading to less enterohepatic circulation (and therefore less metabolism and absorption) and the presence of certain bacterial populations also affecting metabolism. Changes in any of these organs, as well as changes in kidney or renal function, can impact bioavailability. Importantly, drug interactions could occur at any point along this pathway, also impacting bioavailability.

Conclusion

In conclusion, Barnes echoed what other speakers had emphasized: Optimizing nutrition is important. In fact, that is the rationale for functional foods. However, depending on what type of processing methods are used to make the functional food, some of the potential health benefits may not be as great as they are in other, differently processed foods because of reduced bioavailability. In other words, not all soy products are necessarily alike with respect to their health-promoting benefits, because of how different processing technologies alter bioavailability of the compounds that confer those benefits. Moreover, the fact that aging alters the properties of all of various organs that handle bioactive compounds in food creates another major challenge to formulating and providing health-promoting functional foods to older adults. With respect to drug-food interactions, which could occur at any point along the GI pathway and impact bioavailability, Barnes said that is “something we don’t know enough about.”

Is Aging Preventable?

While aging is not preventable, there are interventions that can slow it. The best characterized of these is caloric restriction (CR) without malnutrition. Fontana said hundreds of studies in yeast, worms, and mice and rats have shown that CR can slow aging, with about 10 percent CR increasing maximal life span by as much as 50 percent. As an example, Fontana showed data from Weindruch and Walford (1982) and Weindruch and Sohal (1997) indicating the impact of CR on the lifespan of rodents (Figure 5-3).

FIGURE 5-3

Survival of rodents placed on ad libitum versus calorie restricted diets. This evidence suggests that long term caloric restriction without malnutrition may extend healthspan and maximal lifespan in rodents. SOURCES: Weindruch and Walford, 1982; Weindruch (more...)

Murine models of longevity include

• Ames and Snell dwarf mice,
• growth hormone receptor knock-out (KO) mice,
• insulin-like growth factor-1 (IGF-1) receptor deficient mice,
• klotho overexpressing mice,
• fat insulin receptor KO mice,
• insulin receptor substrate 1 KO mice,
• brain insulin receptor substrate 2 KO mice,
• ribosomal S6 protein kinase 1 KO mice,
• p66shc KO mice,
• type 5 adenylyl cyclase KO mice, and
• Ang II type 1 KO mice.

Are Chronic Diseases Associated with Aging Preventable?

Despite the current “epidemic of obesity” in the United States and associations between excessive adiposity and cardiovascular disease mortality (Calle et al., 1999), cancer mortality (Hu et al., 2004) and other conditions (Willet et al., 1999), Fontana said that his interest in CR is not weight loss. Rather, he is interested in what a 20 or 30 year old man or woman who wants to live a longer and, more importantly, healthier life, can do. He defined healthy aging as the ability of human beings to remain physically and mentally healthy, happy and creative, empowered, active, contributing, and independent for as long as possible. His questions are (1) What interventions, even among lean individuals, promote healthy aging?, and (2)Are chronic diseases associated with aging preventable?

Data from CR in animals suggest that not only do calorie restricted animals live longer lives, they also are more likely to die without any pathologies. In one study, none of the CR animals showed any signs of pathological lesions upon autopsy, whereas only six percent of the animals on a typical diet (i.e., non-CR diet) showed no signs of pathology (Shimokawa et al. 1993). Subsequently, Colman et al. (2009) suggested that CR “works” not only in mice and rats but also in primates. Rhesus monkeys fed a 30 percent CR diet starting in middle age demonstrated a 50 percent reduction in cardiovascular disease mortality and a 50 percent reduction in cancer mortality. Fontana said that the implications of this study are “huge,” because both the CR and control animals were fed a very healthful diet. As far as extension in maximal life span goes, the researchers will not know for another 10 years if CR animals live longer.

He mentioned another study demonstrating even among lean animals with the same body weight, only those fed a CR diet had an extended maximal life span (Holloszy, 1997). Exercise did not increase maximal life span; it only increased average life span, presumably by preventing excessive adiposity and the type of metabolic alterations that typically accompany excessive adiposity (e.g., type 2 diabetes). Only CR slowed down “intrinsic aging.”

Then he discussed a study that he has been involved with for the past two years, where he and his colleagues are examining the effects of CR without malnutrition in a group of healthy volunteers between the ages of 35 and 82. The CR participants (n = 32) are eating 100 percent of their Reference Daily Intake (RDI) for each nutrient and approximately 1800 calories daily. They have been doing this for eight years, on average. The first control group (n = 32) is a group of age and sex-matched U.S. athletes that are equally lean because they are running about 50 miles a week and eating about 2,000 calories daily. The second control group (n = 32) is a group of matched sedentary individuals eating a typical American diet. The researchers are examining the effects of these three different diets (i.e., CR participants, exercisers, and sedentary participants) on body mass index, body fat, hormone levels, glucose tolerance and insulin action, cardio-metabolic risk factors, carotid artery thickness, and arterial elasticity. Only published data are presented here. Fontana et al. (2004) found that CR practitioners had significantly lower serum concentrations of several risk factors, including lower total and low-density lipoprotein (LDL) cholesterol, fasting glucose, C-reactive protein, and blood pressure.

Fontana et al. (2009) found that both CR and exercisers had significantly lower fasting glucose and insulin levels than the sedentary group. Insulin is a risk factor for cardiovascular disease and cancer, and it has been implicated in aging. However, when challenged with a glucose load, the athletes did much better than the CR individuals, suggesting that exercise is much more powerful than CR in preventing type 2 diabetes.

Fontana remarked that clearly hormones and growth factors play a major role in modulating aging in humans. The same changes that have been observed in humans (i.e., reduction in inflammation, insulin, and total testosterone) also occur in mice, rats, and primates, with one important difference. In rats, long-term CR reduces serum IGF-1 concentration by 40 percent (Breece et al., 1991). In humans, however, long-term CR does not reduce serum IGF-1 concentrations (Fontana et al., 2008). IGF-1 is a risk factor for premenopausal breast cancer, prostate cancer, and colon cancer, so the higher the IGF-1 concentration, the greater the risk of developing these cancers (Chan et al., 1998; Hankinson et al., 1998). Not only is IGF-1 a major player in cancer, Fontana said that it is also probably important in the aging process itself.

The Importance of Protein

While CR may not reduce serum IGF-1 concentration in humans, moderate protein restriction does. Fontana and his colleagues realized this when they observed that a group of strict vegans in the study described in Fontana et al. (2008) had significantly lower IGF-1 than either controls or people on a CR diet. The average American obtains about 15 to 16 percent of calories from protein. People on the CR diet had a very high protein diet, obtaining about 24 percent of calories from protein. The vegans obtained only about 10 percent of calories from protein. During the course of the study, Fontana asked some of the CR individuals to go on reduced protein diet, after which their IGF-1 serum levels dropped 25 percent, suggesting that protein restriction is more important than calories in reducing IGF-1.

Noting that the Recommended Dietary Allowance (RDA) for protein is 0.83 g/kg per day and that many people are consuming much more than this (Rand et al., 2003), Fontana challenged workshop participants to consider that while nitrogen balance data may be suggesting that older adults need more protein, not less, IGF-1 data suggest otherwise. Fontana and colleagues are currently studying protein restriction (not just CR) in both animals and humans.

Conclusion

In conclusion, Fontana stated that other factors besides CR, and possibly protein restriction, also affect aging. For example, exercise is very important. Likewise, phytochemical intake may impact antiaging pathways independent of CR and other interventions. Moreover, CR is not necessarily always beneficial. Too much restriction can have detrimental effects and may even lead to death. Plus, various factors such as age, sex, and genetic predisposition might also make a difference. For example, Fontana said that starting a CR diet at the age of 65 is probably not a good idea. CR should be started at an earlier age to control body weight and avoid increased abdominal fat, though Fontana did not specify an age range.

Product Development

Product development—that is, translating aging consumers’ needs into products on the shelf—is a very complex, time-consuming process. It involves everything from “culinary creation” (i.e., making a food that tastes good) to ensuring microbiological stability and regulatory compliance. Kirkwood said that everything that goes into product development can be broken down into four essential “elements”:

• Form (i.e., channel, product form, and package configuration). Form is a key element of the decision-making that goes on around how a product is going to be formulated. For example, will the product be refrigerated, frozen, or shelf stable? Is it something that consumers will want to carry with them? Is it something that people will enjoy preparing for their grandchildren? With respect to package configuration, will the product be single-serve? For aging boomer consumers, ease of use and legibility of preparation instructions are additional considerations (e.g., Kirkwood referred to Brody’s description of the packaging industry’s efforts to develop new types of easy-to-open packages).
• Function (i.e., safety, benefit delivery, and nutritional delivery). Function is another key consideration, with the primary goal being to ensure that a product is safe regardless of consumer need. With respect to benefit delivery, if a product is designed to deliver a specific benefit, that benefit must be validated by science and the necessary ingredient(s) put into the product in a way that ensures bioavailability and that the product is delivering what the package/company claims that it is delivering. For older adults, this means that the health benefit is validated with the targeted age group and that the products actually deliver those benefits specifically to older adults. Nutritional delivery refers to the fact that benefits aside, foods deliver nutrients; therefore, the product in question should be delivering the nutrients it is supposed to be delivering, particularly those nutrients with intake levels that are of greatest concern among older adults.
• Appeal (i.e., taste, texture, and appearance). If a product does not taste or look good, people will not eat it, regardless of its contents. Product development involves extensive sensory work to ensure that the intended benefits are delivered. For aging boomer consumers, additional considerations include vibrancy, potency, and consistency. Vibrancy is the way a food is experienced, for example, its appearance or mouthfeel. Potency refers to a taste profile that hits the “sweet spot” for older adults, especially given that the sense of taste changes with aging. Consistency refers to the texture of a food and the need to develop foods that are not, for example, too crunchy or too hard.
• Affordability (i.e., raw materials, manufacturability, distribution). This is a huge concern, especially in today’s economic climate and especially for aging boomer consumers. Product developers must determine an acceptable price point for the target audience and then design development so that the product can meet that price point. They do this by optimizing raw material usage, working with suppliers to ensure a cost-effective supply chain, and minimizing manufacturing and distribution costs. Also, unit size is important. As people age, they tend to cook only for themselves (i.e., two-people households).

Recommended Maximum Daily Intakes

An audience member asked whether there was any sort of “fudge factor” in Dietary Reference Intakes (DRI) to compensate for variation in sensitivity. The questioner expressed concern about communicating some of the statistics about nutrient intake. For example, if 92 percent of the population has a less than adequate intake of a particular nutrient, how can that information be communicated in such a way that people will not automatically think that they are probably among that 92 percent and therefore are probably going to suffer the consequences? Tucker explained that the RDA is designed to meet the estimated requirement for almost all healthy individuals, which means that many people do not need to meet the RDA. DRI values also contain an Estimated Average Requirement (EAR) which can be used to assess prevalence of inadequacy. She suggested that when 70 percent or more of a group has values below the EAR that there may be reason for concern.

The Importance of Protein in Older Adults’ Diets

Another audience member asked Tucker if she was aware of any studies on associations between amino acids, specifically branched-chain amino acids, and sarcopenia. Tucker replied that most of her work was with whole foods and that she was unaware of any studies on specific amino acids. Barnes remarked that he had recently attended a session on food peptides at a World Food Congress and that, while largely ignored in the United States, many Asian scientists are studying bioactivity of specific amino acids and peptides in foods.

The Mechanism of the Effect of Caloric Restriction on Longevity

Fontana was asked about his thoughts on the mechanism of CR’s effect on improved health and life expectancy. Fontana replied that there is a great deal of research focused on identifying and understanding which mechanisms are mediating the antiaging effects of CR without malnutrition. While data from genetic animal model studies on longevity are filling some gaps in knowledge, he stated that the major mechanisms are unknown. So far, six different animal models for longevity suggest that the IGF-1 pathway is important. Animals with low IGF-1 live longer, healthier lives than animals with high IGF-1, causing Fontana to call IGF-1 “the new frontier.” But other animal models of longevity indicate that there are other factors at play, such as catecholamine signaling and angiotensin activity.

Drug-Nutrient Interactions

Finally, Barnes was asked to elaborate on a parenthetical comment he had made before he began his presentation about disagreeing with Greenblatt’s view on drug-nutrient interactions. Barnes said that he believes there is much more to drug activity than metabolism and the interaction between a drug and a single metabolizing enzyme. By examining only the way that a drug interacts with “your favorite enzyme” and not, for example, how that drug is transported through the body, results in a “rather narrow viewpoint.” Moreover, he emphasized the importance of examining drug-nutrient interactions under the type of stressful physiological conditions that many older adults typically experience.