Association between oral health, dietary intake, saliva and nutritional status

  • Danielle Logan

Student thesis: Doctoral ThesisDoctor of Philosophy


BACKGROUND: Older adults are living longer and this may place an increased economic burden on the healthcare system in terms of chronic disease management. A healthy diet and optimal nutritional status should be encouraged, as this may prevent or improve many age-related diseases and conditions. However, there are a number of factors which may affect dietary intake. Oral health status may be an important factor influencing diet in terms of food choice and eating behaviour. This is because older adults with tooth loss may experience reduced masticatory function and chewing ability, which can lead to the avoidance of foods difficult to eat. If nutritional intake is inadequate or excessive this can contribute to suboptimal nutritional status and may lead to malnutrition, encompassing both under and overnutrition. The current full nutritional assessment in the United Kingdom (UK) is a rather complex and invasive process, involving the collection of a blood sample to assess nutritional state and inflammation. There is a need within the healthcare system for a non-invasive, timely and cost-effective method to provide a biological sample which could help assess nutritional status and support traditional dietary assessment methods. This is where saliva has been suggested as a potential biological fluid that may be used to assess nutritional status and/or dietary intake.

AIMS: The aims of this thesis were to firstly explore the utility of saliva as a biological matrix in the measurement of biomarkers of nutritional status and/or dietary intake. The second aim was to explore the relationship between weight change and inflammatory salivary biomarkers. The third aim was to investigate the associations between oral health status, diet, nutritional status and health outcomes.

METHODS: The aims were achieved by addressing five objectives. This involved: 1) Systematically review existing studies in participants of all ages which had nutrient(s) measured in whole saliva and/or gland specific or glandular saliva, in relation to a nutritional status and/or dietary intake outcome, 2) Exploring whether kits developed for serum could be used to measure levels of the same nutritional biomarkers in saliva samples in a Northern Irish population, 3) Exploring the effect of weight change on inflammatory salivary biomarkers in Northern Irish adults participating in a community-based health programme, 4) Investigating whether oral health status, defined as the number of natural teeth and subsequent prosthodontic rehabilitation, was associated with dietary intake and diet quality in older men, after an average time period of 13 years in the PRIME study, and 5) Exploring associations between oral health status, dietary patterns, body composition, frailty and health outcomes in a cross-sectional pilot study of Northern Irish older adults.

RESULTS: The systematic review on existing nutritional salivary biomarkers, found that a number of potential salivary biomarkers were identified primarily in whole saliva collected from different age groups. The strongest evidence, although still inconclusive and inconsistent in terms of the direction of the biomarker change in relation to nutritional status, suggested that total protein, albumin, glucose, iron, prealbumin, ferritin and total antioxidant status (TAS) may be potential salivary biomarkers of nutritional status and/or dietary intake (Chapter 2). Total protein, albumin, glucose and iron were explored in saliva samples collected from four different studies. The exploratory analysis found that the use of the serum-based kits were not appropriate with the nutritional salivary biomarkers chosen, due to low levels in samples and the high saliva inter- and intra-assay coefficient of variations (CVs) indicating the assays had poor reproducibility (Chapter 3). Different saliva samples, collected in adults, were then tested for inflammatory salivary biomarkers using a customised magnetic Luminex assay. This exploratory analysis found some significant correlations between weight change and changes in inflammatory salivary biomarkers, but they were not consistent across time points and did not remain statistically significant after adjusting for age and gender (Chapter 4). The secondary data analysis of the PRIME study found that having 21 or more natural teeth remaining positively affected future dietary intake of fruit, vegetables, and nuts, and higher diet quality scores including: Mediterranean Diet Score (MDS) and Dietary Diversity Score (DDS), compared to older men with severe tooth loss (i.e. 1-20 teeth or edentate) (Chapter 5). Prosthodontic rehabilitation was suggested to be beneficial for dietary intake and diet quality, especially, in those with at least 21 or more natural remaining teeth (Chapter 5). However, in an exploratory pilot cross-sectional study, no significant association was found between oral health status and MDS in older adults (Chapter 6). The study found that total bone mass, fat free mass and lean muscle, significantly differed according to oral health status (Chapter 6).

CONCLUSIONS: A number of potential nutritional salivary biomarkers have been measured in saliva, but the evidence has proved conflicting, inconsistent and weak, due to many of the studies being of poor/fair quality. The utility of saliva in the measurement of nutritional biomarkers was limited by the current methodology available. To advance this area of saliva research, the development of specific saliva-based kits are required to detect nutritional biomarkers. No significant correlations were found between changes in weight and inflammatory salivary biomarkers, after adjustment for age and gender. Oral health status was associated with future dietary intake and diet quality in older adults in the PRIME study.
Date of AwardJul 2020
Original languageEnglish
Awarding Institution
  • Queen's University Belfast
SupervisorGerry McKenna (Supervisor) & Jayne Woodside (Supervisor)

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