Dietary Habits and Caries Prevalence in Older Adults. A Review

1. Introduction

The older population is significantly increasing worldwide, facing multiple socio-medical and dental needs. Aging is associated with physiological changes that can affect nutrient absorption, metabolism, and overall health status. Therefore, maintaining a healthy diet becomes paramount for promoting longevity and reducing the risk of chronic diseases among older adults.

Even though caries prevalence in the Western world seems to decrease, two age groups continue to record a high prevalence of caries: children and older adults. These two groups are similar in that they depend on carers for their oral health and diet habits. Despite progress in oral health prevention, oral disease is still common in older people due to multiple barriers and risk factors. The prevalence and severity of dental caries vary among different age groups, with older adults often exhibiting a higher burden of untreated caries compared to younger populations (1). Several factors contribute to this disparity, including cumulative exposure to cariogenic risk factors over a lifetime, compromised oral hygiene due to physical or cognitive impairments, and barriers to accessing dental care services (2). Epidemiological studies have consistently demonstrated a high prevalence of dental caries among elderly individuals, particularly those residing in long-term care facilities or experiencing socioeconomic disadvantage (1,2).

Nevertheless, the older adults are known to be a mixed group of three subgroups. Firstly, there are the younger, active people living in the community and taking care of themselves. They are genuinely of good general health, and medical practitioners do not treat them differently than any other adult. Secondly, there is a partially dependent group -they could receive support, but they mainly choose their lifestyle (including diet and oral hygiene). Finally, the third group (older old) can also be frail and depend on carers who dictate their food choices and provide oral care. It is mainly the third group and then the second group that faces the problem of dental caries [1,2].

Caries is prevalent amongst older adults, as there are several aggravating factors such as the decrease of the ability to self-care and, by extension, insufficient oral hygiene, a carious diet, limited exposure to fluoride, xerostomia, receding gums, limited access to dental care, etc. Dietary factors, particularly the consumption of fermentable carbohydrates and sugars, are primary contributors to the development of dental caries. Fermentable carbohydrates in various foods, including bread, cereals, fruits, and starchy vegetables, serve as substrates for acid-producing bacteria in dental plaque, leading to localized demineralization of enamel and subsequent cavity formation. Likewise, sugars, such as sucrose, glucose, and fructose, are metabolized by cariogenic bacteria, producing acidic by-products that promote enamel erosion and caries progression. In addition, removable prosthetic works, which are not carefully cleaned, increase the concentration of dental microbial plaque and create conditions for caries. Root caries is prevalent in the elderly due to gingival recession and root exposure to the oral environment [3,4]. Older adults today tend to retain more of their natural teeth, with edentulism decreasing [5,6]. This means that caregivers (dentists and nursing personnel) of old individuals will have to be trained for treatment in old age and oral hygiene since there is an increasing risk of oral diseases, including dental caries.

The aim of this study was to identify any dietary habits that influence the prevalence of caries (either root caries or coronal caries) and the way that these dietary habits could be different amongst the different groups of the elderly.

2. Methodology

Design and eligibility criteria

To identify the role of the diet of the elderly in the caries process, a scoring review was performed. A scoping review approach was chosen because it allowed the synthesis of information from diverse sources, including theoretical reviews and qualitative and quantitative research. We included scientific papers in English reporting information that answers our question. Reviews, systematic reviews, clinical studies, in vitro studies, and studies in animals were included.

Sources of information and search strategy

Systematic research of the literature was conducted using the following electronic databases, MEDLINE and Scopus, from inception to February 2024. Keywords used for the search included “elderly,” “old people,” “diet,” “caries,” “root caries,” and “older adults” (for example, “elderly AND diet AND caries”). Reference listings of selected articles were hand-searched to identify other possible studies to be included. Two reviewers (GG and CR) independently selected the studies by title and abstract and then by full text according to the eligibility criteria. If there was a discrepancy, a consensus was reached.

Data charting process

One reviewer (GG) extracted relevant data from eligible studies, and an additional reviewer (CR) checked the information for accuracy. An Excel form was then created with information extracted from each article, including authors and journal, year, study objectives, type of the study, and conclusions of the study.

3. Results

The search identified a total of 664 articles, and after they were screened by title and abstract and 56 abstracts because the original article was not in English, more than 575 were removed because of lacking relevance (Figure 1). A total of 33 articles were retrieved and assessed for eligibility. 3 of them were removed because we could not permit the full text, and out of the 30 remaining, 11 were excluded after reading the full text because they were irrelevant to the topic of the search.

3. Discussion

Dental caries

Dental caries is the localized destruction of dental hard tissues (enamel and dentine). It is a dynamic process with repeated circles of demineralization and remineralization of dental hard tissues related to pH alterations of the biofilm. The process is defined as a chemical dissolution caused by acid production by biofilm, frequently exposed to sugars. Literature links the quality of saliva to its increased viscosity, with reduced salivary clearance and, therefore, a more significant time interval in which pH stays below 6.7, which is the critical point for dentine demineralization [7,8]. Dental caries might be the result of lifelong exposure to a dietary risk factor (i.e., free sugars), which means that the influence of carbohydrates is cumulative; we expect people of old age to be more affected because the teeth are exposed for a much more extended period in the dietary risk factors.

Xerostomia

One of the first common symptoms of deterioration in the oral health of older people is xerostomia [9,10,11,12]. Xerostomia or dry mouth is a common symptom, with a wide prevalence range with increasing age [13,14]. The proportion of individuals experiencing xerostomia will continue to rise as the older population grows. The symptom is multicausal and is mainly related to salivary gland disorders, medication use, and various medical conditions [13,15,16,17].

Women seem to have high xerostomia prevalence in comparison to men, mainly after the age of 50 [18]. Also, there is a large amount of literature on the relationship between diabetes and xerostomia [19,20,21]. Medication use is the most common cause of xerostomia [22,23,24,25,26]. As xerostomia is an increasing caries risk, dentists should encourage their patients to increase their water consumption [3]. Also, it is widespread for older people to suck candies or sweets for the relief of the symptoms of dry mouth. This has deteriorating outcomes for teeth, causing caries due to the sugar added in the candies and the frequency of the intake [27].

Diet

The prevalence of coronal and root caries in the older population varies between different studies but is relatively high in the Western world (Table 1).

The increased use of sugar intake that started in the 1970s in these countries determined the prevalence of dental caries. Studies show that risk factors for root caries in older adults include a high intake of sugars (both in a liquid or a solid form), an alteration of their composition preference in this age group, and lower consumption of vegetables and dairy products [31,37,42]. Older people tend to prefer a softer diet, which means that softer food could get stuck more easily in the root areas of the teeth. This preference is because they lose the ability to chew due to lack of teeth but also due to masticatory muscle weakness caused by old age or comorbidities. Any sugars that dental plaque bacteria can utilize as an energy source contribute more or less to the virulence of the microbiota and thus have a cariogenic potential. Sucrose is not only rapidly fermented to acidic end products, but it is also the only dietary carbohydrate that can be transformed into polysaccharides in the plaque. Thus, it is considered the most cariogenic carbohydrate in the human diet [37]. The frequency of carbohydrate intake also plays a crucial part in caries risk in the elderly [34]. It seems that as the frequency increases (regardless of whether they are in a beverage or food), the risk of caries increases with an extreme cariogenic risk when it is above six consumptions per day [28].

Restricting sugar intake is highly recommended by the American Heart Association and the World Health Organization [45]. The American Diabetes Association agreed on a low-carbohydrate diet in 2008 [46]. Similar dietary restrictions are recommended in some European countries, such as Sweden. The Nordic Nutrition Recommendations warn that added sugar intake should be limited from sugar-sweetened beverages and sugar-rich foods to reduce the risk of diabetes, weight gain, and dental caries. These guidelines also clarify that a limitation of such products is necessary to ensure an adequate intake of essential nutrients and dietary fiber [47]. Those dietary recommendations provide a starting point for an optimum diet for preventing dental caries and improving periodontal health.

The primary impact of nutrition on dental caries is understanding that refraining from carbohydrates consumed in solid or liquid form translates into an absence of dental caries [35,41]. The literature shows us that populations living on a diet low in carbohydrates develop dental caries to a shallow extent [48]. Caries process is a consequence of the intake of monosaccharides and disaccharides, including sucrose, glucose, fructose, lactose, maltose, and starch, that are broken down by microorganisms of dental biofilm, which then release acidic end products, with lactate and acetate playing a significant role. Among the different carbohydrates, there is only a tiny variation in acid production ability [39]. This means the local dietary effects depend on what is consumed at a specific time. Many factors influence the intra-oral environment, such as dietary habits, biofilm composition, saliva, and fluoride. Thus, the effect of diet on caries can vary from one individual to another but also from one tooth to another. The enamel will start demineralizing if the pH is lowered below the critical pH level of 5.5– 5.7. Still, when not covered by enamel, a tooth’s dentine or root surfaces have a higher critical pH (around pH 6.2) due to their lower organic content. This occurs after consuming most of the sugars found in candy, soft drinks, fruit juices, or the sugars added to coffee or tea. Complex carbohydrates found in whole foods such as potatoes, rice, cereals, and bread contribute to the caries of the dentine [31,49]. In studies mainly made in animals and in vitro, it is reported that such carbohydrates do not appear significantly cariogenic. However, depending on the frequency of the meals and if sucrose is also present in some form in the diet, they become cariogenic [30,31]. In the in vitro studies, there seems to be a similar pH drop after sucrose or starch solutions, but there is a substantial delay in the demineralization process [29]. When the pH drops slowly, the fluoride ions in the saliva find time to remineralize the tooth structure [40]. The latter could be beneficial when addressing older people because we know that with age, the ion exchange between saliva and tooth is reduced [50,51]. Thus, even these types of carbohydrates could contribute to caries development.

Therefore, the relationship between carbohydrates and dental caries may change during a lifetime as the root surface becomes exposed with age, as periodontitis occurs. This is why older people must get diet recommendations different from those for children and adolescents [38].

The acid-producing Streptococcus species form extracellular polysaccharides in the presence of sucrose but also from fructose and glucose. The energy-rich glycosidic bond between the glucose and fructose parts supplies the energy needed to synthesize polysaccharides. Glucose homopolysaccharides are called glucans, while fructose homopolysaccharides are called fructans. Glucosyltransferases produce glucans, while fructosyltransferases produce fructans. Producing large quantities of polysaccharides from sucrose is essential to S. mutan’s cariogenicity [37].

Dental caries, which is known to be linked to social and behavioral factors, is described as a significant public health problem among older people. Depression is a psychiatric disorder in which appetite and hygiene habits could be affected, often for an extended period, and is particularly common in older, especially those living in nursing homes (late-life depression) [52,53]. In a review held in 2003, it is stated that depression is linked with a more cariogenic diet, containing more carbohydrates than usual and in a softer form that could be stuck into areas of roots, inducing root caries [33]. In addition, oral hygiene and hygiene in general is commonly low on these patients; the risk of root caries is increased [33].

Older people today retain more teeth than earlier generations, often maintaining a so-called “functional dentition,” defined as the presence of at least 20 natural teeth, many of which may be heavily restored with fillings, crowns, and bridges [54,55]. As more teeth are present in the mouth, they are susceptible to oral disease at a more severe and high rate. Root recession, caused either by periodontitis or by wear and is more common in old age, dramatically increases the risk of developing root caries since it is a biological factor necessary for the onset of the disease [55,56,57,58]. Coronal and root surface caries are highly prevalent among old-age populations worldwide, and severe dental caries and periodontal disease are the primary reasons for tooth extractions [54].

Concerning all these, caries risk assessment is an integral part of modern dentistry since more and more people suffer from a disease that could be potentially preventable and manageable. Therefore, early identification of relevant factors affecting older people that could increase caries risk is essential [52]. Higher morbidity associated with chronic disease, the use of medications with xerostomic side effects, frequent carbohydrate intake, and heavy restoration of dentition are additional risk factors that challenge older people. Because of the heterogeneity of the elderly population and the broad spectrum of factors that affect this chronic disease, those at risk can benefit from individually designed preventive programs. Recent dental research in risk assessment has examined new and advanced methods for diagnosing and early predicting caries [60].

A longitudinal study in 2020 revealed no increase in the prevalence of dental caries lesions in older people, indicating that good oral health can be preserved among older adults, resulting in altering the effects of carbohydrate intake [61]. The highest risk for dental caries lesions was among participants with inadequate oral hygiene routines (toothbrushing once a day or less and seldom using interproximal devices) and in need of help in daily living, emphasizing the importance of oral hygiene and collaboration between dental services and community-based health care [61]. Oral diseases, especially dental caries, periodontal disease, and tooth loss, affect general health and can impair quality of life [62].

Alongside the reduction of consumption of sugary foods and drinks, it is also necessary to reduce the consumption of any medicinal products containing sugar that could be prescripted or delivered over the counter to older people and replace them with other, less cariogenic ones [32,34,63]. For example, a very recent clinical study shows that a milk–based nutritional supplement with 8% sucrose used for cases of malnutrition in the elderly increases the risk of coronal and root caries [44]. Also, there are a lot of energy-inducing medicinal products containing carbohydrates [63]. Diet modification may be more difficult in medically burdened elderly whose underlying diseases require frequent meals, i.e., type 2 diabetes, or medicine that should be taken frequently during the day with a full stomach [34,63]. Also, in a recent review, it was concluded that malnutrition affects oral diseases in various ways [43]. It seems that malnutrition, which can be easily reached in the elderly with a low intake of proteins, can induce caries by affecting the saliva glands and, therefore, saliva consistency and quantity [43]. Another way that protein-energy malnutrition can affect caries risk is by increasing enamel solubility [43]. Thus, it is safe to say that maintaining a healthy diet can be beneficial in older people for more than one reason.

In a 2021 study of a Japanese elderly population, it was found that an increase in sugar in beverages and a lower milk consumption led to an increase in the prevalence of caries [64]. The authors attributed this alteration in the diet of older people to taste alterations of old age [64]. In some other studies, it is attributed to economic boundaries, but they all increase caries prevalence [65]. In another study of an Indian population, there was a similar finding that diet alterations with high added sugars lead to more carious lesions [66]. Also, a study in 1995 specifies that coronal caries and root caries have a similar etiology: an increase in sucrose consumption [67].

Root caries

As previously stated, when root surfaces are exposed to the oral cavity due to periodontitis, they become prone to becoming demineralized because the roots are dentine, and exposed organic materials can be degraded by host-derived proteases contained in saliva [68]. We ought to identify root caries risks to set prevention strategies, a field studied in a large part of the literature.

Socioeconomic factors

As a vulnerable group, the elderly population’s oral health status seems to be worsening because of social and economic inequalities [69,70].

Schwendicke et al. reviewed that those with lower educational levels, occupational backgrounds, or incomes were more likely to have a higher risk of caries lesions or experience [71]. Many studies describe the influence of low socioeconomic status and dental caries [72,73,74]. Hobdell et al. (2003) strongly associate oral diseases with socioeconomic status [75]. Studies have shown that people with a low socioeconomic status have poorer oral health status than those with a higher socioeconomic status [76,77]. A study in 2017 in China in a population of elderly also showed a caries prevalence increase with low socioeconomic status, with household income playing a more critical role than education [74]. It could be safe to assume that income alterations can bring barriers to medical and dental care access. Still, some authors also assume that there are alterations in the diet, with a differentiation in the carbohydrates used and a reduction of fibers, proteins, and dairy products due to economic reasons [70].

Household income and educational level are significantly associated with periodontitis and edentate status in older people [77]. It is stated that social status could influence diet due to a total change in oral health perception [66].

Institutionalized patients and frailty

Institutionalized patients could depend on caregivers for their diet and oral hygiene depending on the facility, which also correlates with the patient’s socioeconomic status. This could be why, in some studies, the prevalence of dental caries is increased in institutionalized patients, mainly in cases where they depend on caregivers [78,79]. In other studies, in which the patients are standardized but not frail, there is no increase [4].

Frailty and the physical and mental decline associated with aging significantly impact personal oral hygiene practices [52]. Older people and their caregivers should be informed that the need for caries preventive measures increases with age and get a complete analysis of those.

Caries risk appears to be greater in frail and standardized patients, who tend to feed with even softer food or even supplements. A study from 2014 showed that caries prevalence was higher in patients with oropharyngeal dysphagia, which should be recognized as a significant geriatric syndrome as its prevalence is very high in elderly patients and leads to multiple diseases and risk factors [80].

In extreme frailty conditions, patients could be fed with nursing bottles and medicinal products that would provide proteins and energy to the suffering patient. This means that, more often than not, these products are full of carbohydrates. The method of delivering this product – through nursing bottles is also known to contribute to the increase of dental caries by studies conducted by children [2].

4. Conclusions

Even though diet is a very well-known risk factor for caries (both coronal and root caries), there are very few studies to understand the specific alterations that could prevent the burden of this disease.

Because people live longer and retain more natural teeth than previous generations, oral health care providers must remain attentive to caries risk factors and effectively manage caries throughout the lifespan.

As older adults often refrain from dental care due to various socioeconomic reasons, the role of primary health care professionals in identifying elders needing dental care is crucial.

Dental caries is closely linked to socioeconomic status and, hence, disproportionally affects the poorer and more marginalized groups in society.

It is safe to say that population-wide strategies to reduce free sugar consumption are a critical public health approach that should be a high and urgent priority. Because dental caries results from lifelong exposure to a dietary risk factor (i.e., free sugars), even a slight reduction in the risk of dental caries in the early years is significant in later life. Therefore, to minimize the lifelong risk of dental caries, free sugar intake should be as low as possible from as early as possible.

Population-wide prevention interventions must be universally available and accessible. Such interventions include the use of fluoride and comprehensive patient-centered essential oral health care.