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    An investigation of risk factors for the later development of Type 2 Diabetes Mellitus, using HbA1c as a measure of glycaemia in a group of Auckland school children : a thesis presented in partial fulfilment of the requirements for the degree of Master of Science in Nutrition and Dietetics, Massey University, Albany, Auckland, New Zealand
    (Massey University, 2017) Lawgun, Donna
    Background: A glycated haemoglobin (HbA1c) test is recommended in diagnosing type 2 diabetes mellitus (T2DM) and to identify prediabetics. This test is advocated over other methods due to ease of application and processing. Few studies have examined associations between HbA1c levels and T2DM risk factors (RFs) in children. Aim and hypotheses: To investigate the relationship between HbA1c levels and selected RFs associated with T2DM risk in a group of Auckland children. It is hypothesized that ethnicity and waist circumference (WC) will be reliable indicators of later T2DM risk. Body fat percentage (%BF) will likely be positively correlated with HbA1c level. Study design: A cross-sectional study involving children aged 8-11 years from six Auckland primary schools. Physical measures included weight, height, WC and %BF. A finger-prick blood test was collected for HbA1c levels. Ethnicity, gender, age, usual beverage intake and physical activity (PA) behaviours were assessed by self-completed questionnaires. Stepwise multiple linear regression analysis was used to explore which independent variables best predicted variance in HbA1c level. Results: When children (n=451, 10.4+0.6 years) were classified by glycaemic status, 71 children (15.7%) had HbA1c levels indicative of prediabetes. This was greatest in Pacific (n=29) and South Asian (n=13) children. Maori and Pacific children had higher BMI than European children (p<0.0001). For HbA1c, Pacific and South Asian children had higher levels than European (p<0.0001), as did Maori children (p<0.05). Asian children exhibited high %BF for a low BMI. In regression analysis to explain the variance in HbA1c, WC was the most significant predictor for South Asian, Pacific and Asian children. Conclusion: Ethnicity and adiposity (both central and overall) are key RF for T2DM risk. Waist circumference, waist-to-height ratio (WtHR) and BMI may all be used as measures in screening for T2DM risk. Glycated haemoglobin was a useful screening tool alongside RFs and not dependent on obesity.
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    Six months exclusive breastfeeding : a relational behaviour influenced by actual and virtual social networks : a thesis presented in fulfilment of the requirements for the degree Doctor of philosophy in Midwifery, Massey University, Manawatu, New Zealand
    (Massey University, 2017) Alianmoghaddam, Narges
    Despite widespread consensus regarding the health benefits of six months exclusive breastfeeding for mothers and infants, the prevalence of six months exclusive breastfeeding is very low in developed countries including New Zealand. This research contributes to the literature nationally and internationally through documenting influencing factors among New Zealand women and their family that relate to the practise of six months exclusive breastfeeding. This research is a qualitative study involving face to face postpartum interviews with 30 mothers who prior to the birth of their infants were characterised as highly motivated to breastfeed exclusively for six months. The research participants were recruited from the lower North Island of New Zealand. Initial data were collected using a short questionnaire administered before the birth to record demographic information and to establish an antenatal intention to breastfeed exclusively. An initial postpartum face to face interview was conducted at around six weeks. Each participant was then followed via short monthly audio-recorded telephone interviews until giving up exclusive breastfeeding or until six months after the birth. Social construction is was used as the epistemological framework underpinning the research. A range of social theories, linked to the central theory of social constructionism, were used to highlight the importance of social relationships, social interactions and social support. The theory of “planned behaviour” proposed by Icek Ajzen (1991), the theory of stress, coping strategies and social support proposed by Thoits (1995), theories of “governmentality” and “biopower” developed by Michel Foucault (1972), arguments about the "strength of weak ties” proposed by Mark Granovetter (1973) and theories related to “landscapes of care” suggested by Milligan and Wiles (2010), were used in this thesis to illuminate the findings that resulted from the thematic analysis of the qualitative data. The research was reviewed and approved by the Massey University Human Ethics Committee. The central finding of this research is that six months exclusive breastfeeding practice is not limited to the intentions or actions of the mother-infant dyad; it is socially constructed by actual and virtual social networks around the mother as well as the other relational influences such as historical, geographic, socioeconomic and social contexts of the mother’s life. Additional findings of this research related to the quality of breastfeeding support through social media such as Facebook, Skype and smartphone apps, makes a significant contribution to the New Zealand and international literature in this area.
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    The development and testing of a contextual model for healthcare quality improvement using Lean and the Model for Understanding Success in Quality (MUSIQ) : a thesis presented in partial fulfilment of the requirements for the degree of Master of Quality Systems at Massey University, Palmerston North, New Zealand
    (Massey University, 2017) Wilson, William James
    This study developed a new theoretical model of quality improvement (QI) contextual factors, for QI activity undertaken at the healthcare microsystem level. The Model for Understanding Success in Quality (MUSIQ) (Kaplan, Provost, Froehle, & Margolis, 2012), was aligned with Lean improvement activity using the Toyota Way framework. The aim of the research was to improve the effectiveness of healthcare quality improvement initiatives by providing more understanding of the associations, relative importance and precise functioning of critical contextual factors. A new survey instrument, based on the literature, was developed to collect data and the hypothesised theoretical relationships were tested using the partial least squares path modelling (PLSPM) technique. QI practitioners at a large New Zealand District Health Board were surveyed on a range of contextual factors hypothesised to influence improvement outcomes. All survey participants had recently completed a small-scale improvement project using Lean, or were participants in training programmes that introduced them to Lean thinking and methods. Some participants worked autonomously on improvements of their own selection; others were part of a wider training programme derived from the National Health Service’s (UK) ‘productive ward’ programme. In the healthcare organisational context, the majority of these improvement initiatives were carried out at the microsystem level – initiated and delivered by the teams responsible for the work processes being modified. Survey responses were first analysed via principal components analysis (to examine the dimensionality of the scales) and then PLSPM. The defined contextual factors for ‘Teamwork’, ‘Respect for People’, ‘Lean Actions’ and the influence of negatively motivating factors all reached significance. Defined contextual factors for ‘Previous Experience’ and the influence of positive motivating factors did not reach significance at 5% level. The final model showed a statistically significant, moderate predictive strength, with an overall adjusted R2 of 0.58. This result was an encouraging validation of the microsystem-level layer of the MUSIQ model using Lean as the QI method (context). The relative influence of ‘Teamwork’, ‘Respect for People’, Motivation’, and a mediating mechanism for making process changes (in this instance, Lean) were measured and found to be consistent with the MUSIQ model. Identifying more detailed causal mechanisms (the present model was intentionally parsimonious due to the time frame allowed and the resources available for the research), refining the operational definitions, and developing and testing predictive models for the defined contextual factors are the proposed next steps in the research.
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    'On the path, off the trail' : the relational work of nurses in outreach health : a thesis presented in partial fulfilment of the degree of Masters of Philosophy in Nursing at Massey University, Wellington, Aotearoa New Zealand
    (Massey University, 2017) Martin, Garrick
    This research study draws on the practice reflections of nurses working with people who are homeless and experiencing mental health problems to explore engagement as a core nursing practice in this setting. Therapeutic relationships and engagement are at the heart of nursing practice, and this is especially so in mental health nursing. Homeless and hard-­‐ to-­‐reach clients are an underserved population for mental health services. This research seeks to ‘make visible’ the ways in which mental health nurses uniquely and successfully engage with people experiencing homelessness and marginalisation, which in turn contributes to improved health and social outcomes for those people. Eight New Zealand registered nurses were interviewed and critical thematic analysis used to interpret the resulting data. The research findings were that nurses practicing in this specific homeless health context value relationships as a core nursing intervention. The work of engagement was described as uncertain. The research participants echoed the nursing theory and literature that argues nurses’ relational work is often unseen and undervalued within health systems. Relational work is described as a defining concept for mental health nursing yet the lack of visibility of this skilled work adds to nurses’ experience of uncertainty. The recommendations suggest ways to render visible and hold central the nursing work of engagement.
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    Effect of Faecalibacterium prausnitzii on intestinal barrier function and immune homeostasis : a dissertation presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Nutritional Science, Massey University, Manawatū, New Zealand
    (Massey University, 2017) Maier, Eva
    Various gastrointestinal (GI) diseases, for example inflammatory bowel disease, are linked to impaired barrier function, chronic inflammation and dysbiosis of the resident microbiota. Faecalibacterium prausnitzii, an abundant obligate anaerobe of the healthy human microbiota, has reduced abundance in the GI tract of people with these diseases, and has been suggested to exert beneficial effects. Only a few studies have investigated its mechanisms of action, partly due to the difficulty of co-culturing live obligate anaerobes with oxygen-requiring human cells. The novel apical anaerobic co-culture model used in this study allows this co-culture through the separation of anaerobic and aerobic compartments. This model was used to investigate the effects of live F. prausnitzii (strains A2-165, ATCC 27768 and HTF-F) on intestinal barrier integrity, measured by transepithelial electrical resistance (TEER) of the intestinal epithelial cell line Caco-2, and on immune homeostasis, specifically on Toll-like receptor (TLR) activation. Method development was required to adapt these assays to the novel model and to optimise the growth of F. prausnitzii co-cultured with Caco-2 cells and TLR-expressing cell lines while maintaining their viabilities. Firstly, the optimised co-culture conditions were used to determine the effect of the three F. prausnitzii strains on barrier integrity of healthy and tumour necrosis factor alpha (TNF-α) treated Caco-2 cells. Live and growing F. prausnitzii did not alter the TEER across healthy Caco-2 cells. However, under TNF-α mediated inflammatory conditions, dead F. prausnitzii decreased TEER, whereas live bacteria maintained TEER. Secondly, the TLR activation assay was adapted to be carried out in the novel model. Using the adapted assay conditions it was determined that live F. prausnitzii induced greater TLR2 and TLR2/6 activation than dead F. prausnitzii. Collectively, these results indicate greater immuno-stimulatory effects of live F. prausnitzii, via TLR2 activation, and this effect is potentially linked to its barrier maintaining properties, because previous research showed enhancement of barrier integrity induced by TLR2 signalling. This new knowledge contributes to the understanding of how F. prausnitzii may maintain immune homeostasis in the GI tract. Unravelling the biological mechanisms used by prevalent species of the human microbiota, such as F. prausnitzii, will ultimately allow better comprehension of microbial regulation of GI function.
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    Dimeric procyanidins as modulators of airway inflammation in the context of allergic asthma : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy (PhD) in Human Physiology at Massey University, Manawatū, Palmerston North, New Zealand
    (Massey University, 2017) Coleman, Sara L
    Procyanidins are polyphenolic compounds that have come to be known as biologically active in the context of promoting human health. Epidemiological evidence suggests that populations that consume diets rich in procyanidins are less susceptible to inflammatory diseases. Allergic asthma is an inflammatory lung disease with an estimated 100 million affected individuals worldwide, with New Zealand having the world’s second highest rate. Inflammation at the airway epithelium and infiltration of immune cells, specifically eosinophils, into the lung tissue are two central characteristics of allergic asthma. Thymic stromal lymphopoietin (TSLP) and eotaxin isoforms, eotaxin-1 (CCL11) and eotaxin-3 (CCL26), are three biomarkers of airway inflammation produced by the epithelium. Cell culture models were successfully optimized for CCL11 and CCL26 production in A549 cells. Investigation of procyanidins effect on epithelial TSLP production was not possible because TSLP production in A549 cells was undetectable. Data suggests that dimeric A-type linked procyanidin A2, but not B-type linked procyanidin B1 or B2, is capable of inhibiting IL-4-induced CCL11 production when incubated on A549 cells prior to an inflammatory insult. Co-incubation of A549 cells with procyanidin A2 and procyanidin B2 demonstrated no evidence of a synergistic relationship for inhibiting cytokine-induced CCL11 production. Similarly, A549 cells exposed to procyanidin A2, and to a lesser extent procyanidin B2, had reduced production of cytokine-induced CCL26 production. An inhibition time course demonstrated procyanidin A2 had greatest inhibition efficacy on cytokine-induced CCL26 production when incubated for 2 h prior to an inflammatory insult. Comparison of procyanidin A2 inhibition to the known CCL26 inhibitor, IFN , demonstrated that procyanidin A2 and IFN did not share the same temporal inhibition patterns. Furthermore, experiments investigating concomitant incubation of procyanidin A2 and IFN demonstrated that procyanidin A2 could interfere with IFN –mediated CCL26 inhibition. Two possible mechanisms responsible for the procyanidin A–mediated inhibition of cytokine-induced CCL11 and CCL26 were investigated: the modulation of cytokine receptor expression, and modulation of plasma membrane fluidity. However, there was no evidence to support either of these modes of action. The data presented in this thesis collectively demonstrate the ability of procyanidin A2 to inhibit cytokine-induced eotaxin production from the lung epithelium in vitro and support further investigation of procyanidin A2 as a preventative approach for managing airway inflammation.
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    Molecular epidemiological studies of Campylobacter isolated from different sources in New Zealand between 2005 and 2015 : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy at Massey University, Manawatu, New Zealand
    (Massey University, 2017) Nohra, Antoine
    Campylobacteriosis is one of the most important food-borne diseases worldwide, and a significant health burden in New Zealand. C. jejuni is the predominant species worldwide, accounting for approximately 90% of human cases, followed by C. coli. The first study evaluated whether the time elapsing from sampling to culture has an impact on the recovery rate of Campylobacter, and explored whether some sequence types are more likely than others to be missed due to delayed culture. The study revealed that, whereas delayed culture may affect the recovery rate of Campylobacter, there was no evidence of a bias due to specific sequence types being under detected. The second study aimed to analyse the differences in the Campylobacter viable counts and in population genetic structure between chicken drumsticks and whole carcass meat for retail sale. The results indicate that the Campylobacter population genetic structure did not differ between the two types of retail chicken meat. However, the difference in Campylobacter viable counts suggest that consumption of different chicken meat products may pose different risks of campylobacteriosis associated with an exposure to different infection doses. In the third study, we genotyped C. coli isolates collected from different sources between 2005 and 2014, to study their population structure and estimate the contribution of each source to the burden of human C. coli disease. Modelling indicated ruminants and poultry as the main sources of C. coli infection. The fourth study aimed to genotype C. jejuni isolates collected between 2005 and 2015 from different sources, to assess changes in the molecular epidemiology of C. jejuni following the food safety interventions implemented by the New Zealand poultry industry in 2007/2008. Modelling indicated that chicken meat from ‘Supplier A’ was the main source of C. jejuni human infection before the interventions; but after the interventions, ruminants became the main source of infection, followed by chicken meat from Supplier A. This thesis has made us aware of the aetiology of C. coli infections and the change in the attribution of C. jejuni infections. These findings should be used in developing further strategies to reduce the total burden of human campylobacteriosis.
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    Occupational leptospirosis in New Zealand : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy at Massey University, Institute of Veterinary, Animal and Biomedical Sciences, Palmerston North, New Zealand
    (Massey University, 2016) Sanhueza Frigolett, Juan Manuel
    Although a decreasing trend of human notifications was observed from 2001 to 2014 (Chapter 1), the incidence of human leptospirosis in New Zealand continues to be higher than in other high-income countries and affecting predominately people occupationally exposed to livestock (i.e. abattoir workers and farmers). Additionally, evidence suggests that leptospirosis may have a higher detrimental effect on production in deer compared with beef cattle or sheep. It was also observed that vaccination against Leptospira of not previously infected animals reduce the risk of urinary shedding of leptospires after challenge, and that there is limited evidence supporting or disproving that maternally derived antibodies interfere with the effect of vaccination when animals are vaccinated at a young age. When sero-positivity was defined as a serum microscopic agglutination test (MAT) titre of ≥48, 6.6% of farmers (Chapter 2) and 5.1% of veterinarians (Chapter 3) were sero-positive to at least one of five Leptospira serovars (Hardjo-bovis, Pomona, Copenhageni, Ballum, Tarassovi). Veterinarians had a higher risk of being seropositive when they slaughtered cattle or pigs at home or worked in a mixed animal practice. Assisting calving of cattle or deer, farming deer alone or in combination with cattle and/or sheep, flat terrain on farm, and abundance of wild deer on farm, increased Leptospira sero-positivity of farmers. Apart from vaccinating farmed livestock, increased awareness of such risk factors and the use of protective equipment may reduce the human leptospirosis incidence in these occupational groups. Similar to earlier observations in abattoir workers, Leptospira sero-prevalence of farmers and veterinarians was associated with the recall of influenza-like illness of sampled individuals. Using the estimated incidence of influenza-like illness attributable to Leptospira infection (population attributable risk) of veterinarians (0.05%), farmers (1.3%) and abattoir workers (2.7%), we quantified the burden of human leptospirosis in terms of disability-adjusted life years (DALYs) and economic cost of infection; the latter including the cost of vaccination, which is primarily used in dairy cattle (Chapter 4). Annual DALYs were estimated to be 0.43 per 100,000 people in New Zealand, and 16.76 per 100,000 people when only considering the occupationally-exposed population (abattoir workers, farmers, veterinarians). This ranks leptospirosis in New Zealand’s high-risk population similar to worldwide estimates of DALYs for rabies and dengue. The total annual cost of leptospirosis due to human disease (i.e. treatment and absence from work); production loss in deer, beef cattle, and sheep; and the cost for vaccinating them was estimated to be NZ$25.36 million. One third of this total was attributed to vaccination of dairy cattle. The annual cost of human treatment and workplace absence due to severe and mild leptospirosis was NZ$4.49 million. Total lost production cost was NZ$11.31 million, half of which was attributable to reproductive and growth reduction in deer. No estimates are currently available from any other country for the public health burden and the overall economic loss including farmed livestock for this disease. Since vaccination of livestock is currently regarded as the most effective means of preventing human exposure, the literature on the efficacy of Leptospira vaccines for preventing urinary shedding was systematically reviewed (Chapter 5). The metaanalysis of vaccination trial results, using articles with sufficiently detailed data, resulted in a pooled vaccine efficacy estimate of 82% when shedding was assessed by culture. The findings of this thesis contribute towards a better understanding of the public health burden, economic cost, infection sources for humans, and the efficacy of vaccination for reducing the risk of Leptospira urinary shedding in domestic livestock
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    Exploring body composition and metabolic health amongst NZ European, Pacific Island and Māori women participating in the women's EXPLORE study : a thesis completed as part of the requirements for Master of Science in Nutrition and Dietetics at Massey University, Albany Campus, Auckland, New Zealand
    (Massey University, 2017) Whitford, Amanda
    Background: In New Zealand, 31.6% of adults are obese. Significant ethnic health inequalities exist; Pacific Islanders and Māori have the highest rates. Objectives: To investigate the body composition and metabolic health profiles of healthy NZ European, Pacific and Māori women participating in the women’s EXPLORE study. Methods/Design: Cross sectional design investigating 233 European, 91 Pacific and 84 Māori women. Different body mass index (BMI) and body fat % (BF%) defined body composition profiles were analysed for anthropometric measurements, body fat location, and metabolic biomarkers. Results: Obese (BF%) Māori women had higher android fat mass than obese (BF%) Europeans (2.53kg vs 2.23kg) with no difference in waist circumference (WC). Non-obese (BMI) Māori had higher WC than non-obese (BMI) NZ Europeans (78cm vs 73.5cm) with android fat differences. Regardless of body composition grouping, no ethnic differences were found for BF%. Obese Pacific women had higher HOMA-IR (5.12-5.45) and insulin (24.28- 23.28mU/L) than obese Europeans (2.10-2.61 and 10.07-11.24mU/L respectively), as did obese Māori (3.64-4.35 and 16.76-19.41mU/L respectively). Body composition measures with highest sensitivity across all biomarkers assessed were BF% ≥30 for Europeans, both BF% ≥30 and BMI ≥25 for Pacific, and BMI ≥25 for Māori. Conclusion: Māori and Pacific women had significantly higher glucose metabolism markers than NZ Europeans despite no differences in BF%. When comparing Māori to NZ Europeans, a higher WC was not always related to a higher android fat mass or vice versa, suggesting that WC may not be an accurate representation of abdominal fat for Māori. In spite of ethnic differences, BF% ≥30 and BMI ≥25 appear most sensitive to detect high biomarkers compared to abdominal measurements.
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    An investigation into the link between vitamin D status, erectile dysfunction and cardiovascular risk factors in ageing men in New Zealand : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Nutritional Science at Massey University, Palmerston North, New Zealand
    (Massey University, 2016) Quilter, Merrin Louise
    Background Cardiovascular disease (CVD) is the leading cause of death worldwide, particularly amongst ageing males. Prevention and/or early identification and effective intervention are essential in the fight against CVD. Erectile Dysfunction (ED) is a prevalent and multi-factorial condition that is now accepted to be an early marker of subclinical CVD: the common denominator is endothelial dysfunction. Both the enzymatic capability for bioactivation of Vitamin D and the vitamin D receptor (VDR) are expressed in endothelial cells and vitamin D may play a role in endothelial function. Vitamin D deficiency (serum 25-hydroxyvitamin D (25(OH)D) concentrations ˂50 nmol/L) is a worldwide pandemic and serum 25(OH)D levels ˂75 nmol/L may result in metabolic and vascular deterioration leading to endothelial dysfunction, ED and CVD. Assessment of erectile function can be used to identify otherwise asymptomatic men at high risk of developing clinical CVD, at a time when effective intervention may prevent, delay or reverse its progression. Vitamin D status may be associated with ED and CVD risk and could help improve erectile function and vascular health. Objectives The aim of this research was to investigate the postulated link between vitamin D status, ED, and CVD risk factors. The objectives were (1) to assess the prevalence of ED (using the 5-item International Index of Erectile Function (IIEF-5)) and its associated sociodemographic, lifestyle, and medical correlates in New Zealand (NZ) men aged 40-70 years; (2) to investigate the relationship between vitamin D status (serum 25(OH)D concentration), ED and other CVD risk factors in men aged 40-70 years living in the Manawatu region of NZ; and (3) to examine the impact of common VDR gene (VDR) polymorphisms on this relationship. Method Two thousand men aged 40-70 years were randomly selected from the NZ Electoral Roll and sent an anonymous postal survey designed to assess the prevalence of ED and its sociodemographic, lifestyle, and medical risk factors. Six hundred men aged 40-70 years living in the Manawatu region were randomly selected from the NZ Electoral Roll and invited to participate in an observational study designed to provide a comprehensive health profile of self-reported healthy men and investigate the relationship between vitamin D status, ED, and a range of CVD risk factors. Eligible participants (n=100) completed a comprehensive health assessment including a medical history, anthropometric and cardiovascular assessment, fasting blood sample, computer-based questionnaire, a submaximal fitness test and a handgrip iv strength test. Blood samples were assessed for four common VDR polymorphisms (rs11568820 (Cdx2), rs10735810 (FokI), rs1544410 (BsmI) and rs731236 (TaqI)) using polymerase chain reaction-high resolution amplicon melt (PCR-HRM) analysis. Results The survey showed 38.4% of respondents presented with ED (IIEF-5 ≤21). Older age, non-European ethnicity and current smoking were significant independent predictors of an increased risk of ED, while a high household income and regular vigorous physical activity (PA) were deemed protective. The observational study showed 30 men presented with ED and a further 37 men had <75 nmol/L 25(OH)D. There was a weak positive correlation between IIEF-5 scores and 25(OH)D levels (rs=0.238, p=0.017). Men with <75 nmol/L had lower IIEF-5 scores compared to men with ≥75 nmol/L 25(OH)D (22(7) vs. 24(3), p=0.001). Men with ED had lower 25(OH)D levels compared to men without ED (74.5(34) vs. 84.5(24), p=0.062). Every 1 nmol/L of 25(OH)D predicted a 2% decrease in the age-adjusted risk of ED (age-adjusted OR=0.98 [0.96-1.00], p=0.046). The PCR-HRM analysis showed that the Cdx2, FokI and BsmI polymorphisms were all significantly associated with an adverse cardiovascular risk profile. The Cdx2 G allele was associated with lower IIEF-5 scores compared to the A allele (23(4) vs. 24(2), p=0.008) and the GA and GG genotypes were predictors of an increased age-adjusted risk of ED (age-adjusted OR=18.78 [1.98-178.60], p=0.011 and 8.53 [1.00-72.73], p=0.050 respectively). However, Cdx2 was not found to modify the age-adjusted association between 25(OH)D levels and ED (multi-adjusted OR=0.97 [0.95-1.00], p=0.032). Conclusions These results suggest that over a third of NZ men aged 40-70 years suffer from ED and it is associated with sociodemographic, lifestyle and medical factors similar to CVD. Low serum 25(OH)D is associated with the presence and severity of ED in a self-reported healthy population. Common VDR polymorphisms are also associated with ED; however, they do not modify the association between serum 25(OH)D and ED. A randomised placebo-controlled human intervention trial is warranted to investigate whether improving vitamin D status in men with vitamin D deficiency and ED ameliorates symptoms and reduces the risk of CVD.