- Title
- Biological markers in assessing dietary intake in adults
- Creator
- Clarke, Erin Drury
- Relation
- University of Newcastle Research Higher Degree Thesis
- Resource Type
- thesis
- Date
- 2021
- Description
- Research Doctorate - Doctor of Philosophy (PhD)
- Description
- Polyphenol-rich diets, containing large amounts of vegetables and fruits are showing promise in prevention of chronic conditions such as cardiovascular disease and type 2 diabetes. However, the assessment of polyphenol intake relies on dietary assessment methods such as 24-hour recalls and food frequency questionnaires that are linked to limited food composition databases in order to estimate intake. These self-reported dietary assessment methods can provide detailed information on the amount, type and timing of intakes. However, these methods are at risk of systematic, random and differential errors. Urinary polyphenol metabolites are promising biomarkers that could be used to help determine measurement error related to self-reported polyphenol intakes. Limited research has been undertaken to determine the strength of the relationship between dietary polyphenol intakes and urinary polyphenols, particularly using spot urine samples. Therefore, the aim of this thesis is to explore the strength of the relationship between self-reported dietary polyphenol intake and spot urine polyphenols. Four studies were undertaken to address thesis aims. The first study was undertaken to explore the benefits of consuming a diet high in vegetables and fruits. This was done by undertaking a pre-post study to determine whether there are sex differences in anthropometric outcomes amongst participants asked to consume a diet high in vegetables and fruit. This study did not identify any differences between males and females in regard to anthropometric outcomes. However, it did identify that males had a greater reduction in their energy intake while females had a greater reduction in intakes of energy-dense, nutrient-poor foods. Findings from this study identified the potential of differential error occurring as participants were aware of the study aims from the outset. This may have resulted in over-reporting of vegetable and fruit intakes. The risk of differential errors raised the question of how could the inclusion of a biomarker that reflects intakes of vegetables and fruits improve future studies? A scoping review was then undertaken to summarise which urinary metabolites have been used to evaluate dietary intakes. Reliable biomarkers were identified for wholegrains (alklyresorcinols), soy (isoflavones) and sugar (sucrose and fructose) intakes. Polyphenol metabolites appeared to be promising biomarkers of polyphenol-rich foods, however few polyphenol metabolites had been consistently used in the literature. Secondly, the review concluded that spot urine samples appeared to be a lower burden, and promising as an alternative to 24-hour urine samples. Again, limited research had been undertaken to evaluate the application of spot urine samples. Next, the relationship between spot urinary polyphenols and intakes of polyphenols from vegetables and fruit were explored in a study in adults with overweight and obesity, in which participants were asked to consume a diet high in vegetables and fruits. Significant relationships were identified between total urinary polyphenols and intakes of total polyphenols (rs=0.47) and fruit polyphenols (rs=0.38), however these correlations were not significant across all study time points (baseline, week 2 and week 10). Hippuric acid was significantly correlated with vegetable polyphenols (rs=0.39) at baseline only. Linear mixed models identified that intakes of total polyphenols, but not vegetable and fruit polyphenols, explained the concentrations of total urinary polyphenols. These models showed that for every 1mg increase in total polyphenol intakes there was an increase in total urinary polyphenols concentrations by 16.3nMol/g creatinine. Therefore, spot total urinary polyphenols may be a better biomarker of polyphenols intakes from all polyphenol-rich food sources. Following on from the previous study the strength of the relationship between spot urinary polyphenols and polyphenol intakes from a variety of polyphenol-rich food sources was explored in young adults. Total urinary polyphenols were consistently correlated with total polyphenol intakes which supports their continued use as a biomarker of total polyphenol intakes. Hippuric acid on the other hand was moderately correlated with total polyphenol intakes and tea and coffee polyphenol intakes but other food group specific polyphenols showed inconsistent findings. These findings were consistent with other literature. Stronger relationships were observed between polyphenol intakes and total urinary polyphenol metabolites and hippuric acid in this chapter compared to the previous chapter, the differences observed may be explained by the differences in age and BMI between the two studies. Further research is required to validate both total urine polyphenols and hippuric acid as biomarkers of polyphenol intakes in adults with overweight and obesity and young adults. In conclusion, this thesis identified a relationship between spot total urinary polyphenols and total polyphenol intakes. However, inconsistencies in the strength of the relationship between spot urinary polyphenols and dietary polyphenol intakes across time points was evident. Future research should further explore the application of 24-hour vs. spot urine samples to gain greater insights into the application of spot urine samples. Further research into the effects of fasting and the influence of the food matrix on the half-life of urinary polyphenol metabolites will also help provide more insight into the ideal timing and application of spot urine samples. Additionally, studies should test the utility of repeat spot urinary polyphenols collected across the day, rather than one spot urine sample to determine the strength of the relationship with intake. Overall, further research examining spot urinary polyphenols time-response relationship with intake, robustness and reliability as a biomarker is required to validate spot urinary polyphenols before they can be used to assess measurement error within free-living intervention studies.
- Subject
- polyphenol metabolites; biomarkers; dietary intake; adults; thesis by publication
- Identifier
- http://hdl.handle.net/1959.13/1504676
- Identifier
- uon:55563
- Rights
- Copyright 2021 Erin Drury Clarke
- Language
- eng
- Full Text
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| View Details Download | ATTACHMENT01 | Thesis | 82 MB | Adobe Acrobat PDF | View Details Download | ||
| View Details Download | ATTACHMENT02 | Abstract | 286 KB | Adobe Acrobat PDF | View Details Download |