N of subjects
Flynn 2014 
Karagiannis 2014 
Steele 2013 
Karagiannis 2011 
Foley 2008 
Loeb 2003 
Whelan 2001 
Goulding 2000 
Garon 1997 
Groher 1987 
The benefit of texture-modified foods and/or alteration of fluid viscosity was evaluated in five RCT [40, 84–87] and one quasi-experimental study . Although four [40, 84, 85, 87] of five RCT studies evaluated pneumonia, it was difficult to meta-analyze the overall benefit due to heterogeneity of interventions, timing and duration of therapy and conditions of study population. Sample sizes across studies were small, ranging from 20  to76  and the event rates for pneumonia were low. In one trial , the simultaneous manipulation of solid textures and fluid viscosities makes it difficult to establish which component (solid or liquid) was associated with pulmonary benefit. In summary, although modifications in dietary textures and fluid viscosities are common interventions there is scant empirical evidence of their medical effectiveness.
29.6 Impact of the Consistency of Food Substances on Aspiration Pneumonia
29.6.1 A Prompt Report from our Study
The importance of oral intake versus enteral tube feeding is widely understood from the physical, mental, social and ethical aspects. It is recognized that oral intake can improve the organic response to stress and thus facilitate the recovery of patients after surgery . Recently, clinicians have been attempting to promote oral intake. However, once oral intake is achieved, less attention has been paid to the consistency of food and to returning from modified-texture foods to regular solid food. It is hypothesized that regular food which requires mastication should promote masticatory function, salivary secretion and lower risk of dental diseases, and consequently promotes nutritional status and development of resistance against infections. Thus, a study considering the relationship between the consistency of food substances and the incidence of pneumonia in elderly people living in a welfare facility was conducted and presented briefly .
The subjects were 154 residents (29 males and 125 females; age, mean 87.9 years, range, 69–102 years). The following data were obtained from the facility’s records: consistency of food substances, their caloric intake, their general health status (BMI and history of pneumonia), oral health (number of teeth, oral function, dental diseases, and amounts of ten specific microorganisms in the oral cavity). As results, solid food eaters were found to have a lower incidence of pneumonia (11.4 %) than paste food eaters (44.4 %) and those fed liquids through a gastrostomy tube (55.6 %) (χ 2, P < 0.001). This may be because of the higher calorific intake (mean ± SD; 1513.0 ± 135.3 kcal) of regular food eaters compared to paste food eaters (1362.2 ± 178.8 kcal) and those receiving nutrition through a gastrostomy tube (9056.6 ± 176.5 kcal) (ANOVA, P < 0.001). Regular food eaters had better oral function (χ 2, P < 0.001) and fewer microorganisms (ANOVA, P < 0.001). Since this was a cross-sectional study, it was not possible to ascertain causal relationships. However, the results suggest that the consistency of food substances which require mastication has some influence in lowering the incidence of aspiration pneumonia among the elderly.
29.6.2 Advantage of Mastication of Food
22.214.171.124 Promoting Physical Activity
Mastication promotes the production of saliva. Saliva plays a vital role in food oral processing and antimicrobial function . Human saliva consists of electrolytes, mucus, glycoproteins, enzymes, and antibacterial compounds such as secretory IgA and lysozyme . Functions are protection and lubricant (coating oral mucosa to protect from trauma), digestion (moistening foods and helping to create a food bolus, containing enzymes to digest starches and fats), antimicrobial function (a mechanical cleansing action and a specific, e.g., IgA, and a non-specific immunologic action e.g., lysozyme, lactoferrin and myeloperoxidase), pH maintenance (containing various ions which act as a buffer), remineralization of teeth, a taste mediation . Promoting saliva production results in better oral hygiene and improvement of digestions.
Physiologically, oropharyngeal colonization by pathogenic organisms is prevented by the mechanical clearance provided by chewing and swallowing .
Helping Enzymes for Digestion
Mastication breaks the food into smaller pieces, increasing efficiency of the digestive enzymes by creating more surface area on food particles for attachment of enzymes.
Using organs, disuse syndromes can be prevented. A physical can prevent disuse syndrome. Physical inactivity predictably leads to deterioration of many body functions. Regular food requires more chewing time than modified-texture foods, thus it is expected to activate related organs. Though there is insufficient evidence concerning the elderly, gum chewing decreases time to flatus and first defecation after surgery  and chewing and a fiber rich diet is suggested to help development in children .
Although this theory is not confirmed in humans, the relationship between mastication and cognitive impairment has been studied in various animal models [95, 96]. Three mechanisms explaining these animal studies were proposed to relate to a neurogenesis in the part of the brain that is associated with cognition: an increase in corticosterone and a decrease of hippocampal glucocorticoid associated with stress, a disruption of cholinergic neurotransmitter system associated with learning ability, and spatial memory . In humans, though several studies have been undertaken, there is insufficient substantial evidence to demonstrate the relationship .
126.96.36.199 Better Nutrition
Although it is widely believed that altering the consistency of foods and fluids can help individuals with dementia and swallowing difficulty more safely and more efficiently, the use of modified-texture foods, particularly pureed diets, has been implicated in the high prevalence of undernutrition . There is little clinical evidence to explain how the use of modified-texture foods causes undernutrition, but previous studies have found that modified-texture foods, specifically pureed types, offer poor nutritional value compared with regular foods [99–101]. The modified-texture foods may also lead to dehydration and malnutrition. It can be unpalatable and the choice of food that is recommended may be limited [102, 103]. One study reported that if the consistency of food was changed from paste to soft solid food which requires mastication, people improved through the intervention (n = 13) by gaining weight .
A result of satisfaction survey among residents in long-term care indicates that food is the topic with the most variability, reflecting not only a high level of interest in this important daily activity, but also a range in satisfactions . They may resist consuming modified texture foods instead of appealing the texture and taste because they are often unappealing in their appearance, texture, and taste . Some studies have shown that patients may be embarrassed eating pureed foods in front of other people, resulting in their social isolations . Niezgoda et al.  reported several issues and challenges in relation to modified-texture foods.
29.6.4 Consideration of Modified-Texture Foods for the Elderly
Assessment of eating ability and adapting modified-texture foods has not been standardized in clinical settings . One study indicated that among nursing home residents, 91 % of nursing home residents with modified-texture foods were placed on overly restrictive diets . Only 5 % of these patients were identified to be on an appropriate diet level matching their swallowing ability and 4 % of patients were placed on diets above their clinically measured swallowing ability. Furthermore, low acceptability and resulting poor adherence to modified-texture food/liquids can contribute to increased risk of inadequate nutrition in elderly patients with dysphagia.
The phenomenon of elderly persons not eating is observed daily in clinical practice. However, assessment of the causes is highly complex and providing proper care is difficult. If caused by dysphasia from stroke or dementia, the risk from diseases and comorbidity should be carefully taken into consideration and provide medical treatment. If caused by poor oral conditions such as losing teeth or edentulism [110, 111], dental treatment should be the first choice. If caused by the physiological changes that occur with aging, such as decreased sense of taste, hunger, and appetite, or fatigue after hospitalization, promoting functions may be taken into consideration to avoid disuse syndromes. Thus, it is important to keep personal history records and watch individuals carefully as well as to carry out further researches which will develop standardized care.
29.7 What Further Research Needs to be Done?
Review articles referred in this part concluded that there is a clear and pressing need for high-quality research to identify effective treatments. In the hierarchy of research designs , ‘high-quality research’ may indicate high-quality RCTs, which are considered to be evidence of the highest grade as “gold standard”. However, is sufficient evidences provided by RCTs for better clinical practice? The demerits of RCTs are well-known, as well as their advantages. Black  discussed many limitations and explained the necessity of observational studies. The issues of limitations of external validity is important. The RCTs are designed to maximize their internal validity to produce similar groups by random allocation. Usually, participants have been selected using strict inclusion and exclusion criteria, consequently characteristics of a study population were limited. In addition, other issues include difficulty in studying rare events, ethical problem, narrowing of the studied question, costs and time .
Two studies published in The New England Journal of Medicine in 2000 found that observational studies (with either a cohort or a case–control design) do not overestimate the magnitude of the effects of treatment as compared with those in RCTs [114, 115]. In addition, the range of the point estimates for the effect was wider for RCTs than for the observational studies, possibly due to the limitations of external validity.
As to compensate for the RCTs, comparative effectiveness research (CER) is proposed. CER is the direct comparison of existing health care interventions to determine which work best for which patients and which pose the greatest benefits and harms in the real world. Horn and Gassaway  extend the concept to develop practice-based evidence for clinical practice improvement (PBE-CPI) study methodology. PBE-CPI incorporates natural variation within data from routine clinical practice to determine what works, for whom, when, and at what costs. It uses the knowledge of front-line caregivers, who develop study questions and define variables as part of a transdisciplinary team. Its comprehensive measurement framework provides a basis for analyses of significant bivariate and multivariate associations between treatments and outcomes, incorporating patient differences, such as severity of illness . PBE-CPI studies can uncover better practices more quickly than RCTs or sophisticated statistical methods, while achieving many of the same advantages .
Open Access This chapter is distributed under the terms of the Creative Commons Attribution Noncommercial License, which permits any noncommercial use, distribution, and reproduction in any medium, provided the original author(s) and source are credited.
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