Providing Healthy and Safe Foods As We Age Workshop Summary (2010) / Chapter Skim
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3 Physiology and Aging
3 Physiology and Aging
Pages 39-60
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From page 39... ...
at Tufts University, Boston, Massachusetts, who spoke about changes in the immune system that accompany aging and the importance of considering underlying genetic variation in immunity when evaluating nutrition in aging populations. Meydani emphasized the distinction between incidence of infectious disease and severity of illness resulting from infection.
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For example, when a food poisoning episode occurs in a nursing home, the younger caregivers can usually recover, but the elderly people often suffer greater complications that may result in death. To illustrate the impact that aging has on the severity of infectious disease, Meydani described a Salmonella typhimurium study that she and her colleagues conducted using a murine model system (Ren et al., 2009)
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In humans, any of a number of T cell-mediated functions could be contributing to the link between aging and infectious diseases (as well as between aging and cancer) , including decreased antibody production, a decreased delayed-type hypersensitivity (DTH)
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Meydani also suggested that micronutrient status in older adults could be a determinant of susceptibility to infectious disease. Taken together, all of these changes that occur with aging raise the question: Can something be done to prevent age-associated immune dysfunction and/or viral evolution?
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Upper respiratory infections tend to be viral, whereas lower respiratory infections tend to be bacterial. However, in these various studies, not all of the older adults who received vitamin E supplementation showed improvements in immune response.
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The next step is to determine whether zinc supplementation in older adults with initially low serum zinc levels actually reduces the incidence of pneumonia. She also mentioned that this high level of zinc deficiency is not unique to nursing home residents; in another study, she and her colleagues found that 22 percent of independently living older adults had low serum zinc levels.2 Vitamin B Meydani described a study that she conducted in collaboration with Rob Russell (Meydani et al., 1990)
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From page 45... ...
or a high-level fish oil diet (0.54 percent of calories) for six months and showed that, yes, diets enriched with fish-derived polyunsaturated fatty acids significantly reduced production of PGE2 as well as production of the pro-inflammatory cytokines interleukin 1β, TNF, and interleukin 6 (Meydani et al., 1993)
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When fish oil alone is administered to older adults, delayed-type hypersensitivity (DTH) levels decrease.
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; participants were exposed to either 10 percent or 30 percent reduced calorie diets; and DTH was used as an indicator of immune response and measured at both baseline and after 6 months. Among other findings, the study showed that both the 10 percent and 30 percent reduced calorie diets led to significant improvements in immune responses based on DTH measurements.
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The most important clinically relevant changes that occur in healthy older adults are in the oropharynx, with poor oral health being associated with poor diet quality, micronutrient deficiencies, involuntary weight loss, and an increased risk of cardiovascular disease. Oropharynx Some of the most important changes that occur with aging and that impact nutritional status occur in the oropharynx.
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Finally, gastric emptying tends to become delayed with mixed or solid meals but not with liquid meals, although a clinically significant delay usually reflects an underlying disease condition (e.g., diabetes)
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While lactase activity declines, sucrase and maltase activities are unaffected. By and large, small intestinal integrity remains largely intact in healthy older adults, with normal mannitol absorption measurements.6 While decreased nutrient absorption is exhibited with aging, Jensen reiterated that significant changes in absorption of any nutrient usually reflect an underlying pathology.
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Other typical changes include an increased pressure threshold for eliciting a sense of rectal filling, decreased rectal elasticity, a thickening of the internal anal sphincter, and impairment in anal canal resting and maximal squeeze pressures. While older adults, especially women, report an increased frequency of fecal incontinence, this is usually associated with colorectal surgery or disease.
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are likely to be assimilated. • Oral health in older adults, however, is a critical concern, with poor oral health leading to poor diet quality, micronutrient deficiencies, and involuntary weight loss.
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. For example, the National Geographic Smell Survey, a classic study conducted in the 1980s, demonstrated higher thresholds among older adults for several different odorants (Wysocki and Gilbert, 1989)
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Figure 3-3, editable tends to decline "across the board," making it a little easier to increase palatability through odorant supplementation. In a more recent epidemiological study, the Beaver Dam Study, which was mostly focused on hearing but also involved collecting olfactory data, over 60 percent of the people involved in the study over the age of 80 years had impaired sense of smell, and close to 25 percent of people over the age of 50 years were affected (Murphy et al., 2002)
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On the other hand, most flavorings are combinations of odorants, tastes, and irritants, and therefore adding more irritant can have an unpleasant burning effect unless the intensities of other flavor compounds are increased as well. Most Older Adults Enjoy Eating Despite chemosensory losses, most older adults nonetheless enjoy eating.
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Because of something known as negativity bias, people pay more attention to harmful experiences than to potentially beneficial experiences. So the effect of chemosensory loss is much greater for unpleasant flavors, which leads to a potential loss in what are known as gate-keeping functions, for example the ability to detect spoiled food or salt.
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Both animal (rodent, primate) and human studies showed that fish oil must be combined with vitamin E in order to avoid the adverse effects associated with cell-mediated immunity.
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If so, how might this impact public policy around nutrition in aging populations? Meydani replied, "That is an excellent question." She said that she is considering that question in her own research, specifically how nutrition during early fetal life and during childhood could impact the development of chronic and infectious diseases later in life.
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Prospective studies have found that people with severe olfactory loss develop more memory deficits in general, even if they do not develop Alzheimer's per se. However, she noted, "it is much more common to have a loss of sense of smell than to have Alzheimer's!
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