PhD Studentship in Nutrient interaction and carotenoid skin colour: a signal of human health

Further to their work relating skin colour to health and attractiveness, the Perception Lab at St Andrews, headed by Dave Perrett,  would like to advertise a PhD studentship for applicants with a background in Psychology, Biological Sciences or cognate discipline.

A 4-year BBSRC studentship is available from September 2016. The studentship offers the opportunity to work in an academic setting on a project pertinent to health, and will lead to a PhD degree in Psychology from the University of St Andrews.

Supervisor 1:              Professor David Perrett, School of Psychology & Neuroscience

Supervisor 2:              Dr Gozde Ozakinci, School of Medicine

The student

You will have a good (at least 2.1 or equivalent) undergraduate degree in psychology, biology or a cognate discipline. An interest in face perception, biological underpinnings of health, and application of research is desirable. You will have some responsibility in communicating findings and are likely to have opportunities for public engagement and Knowledge Transfer.

The Project: Nutrient interaction and carotenoid skin colour: a signal of human health

Background. Consumption of carotenoid pigments via fruit and vegetable intake has a visible impact on human skin colour (Whitehead et al. 2012). Carotenoid-based colouration of skin is seen as healthy and attractive across different ethnicities, and visualisation of its impact can motivate long-lasting dietary improvement (Whitehead et al. 2014). As antioxidants, carotenoids may contribute to health by their capacity to neutralise reactive oxygen species associated with disease and ageing. Skin carotenoids may signal health because they reflect particular aspects of healthy diet and are expended during illness.

While carotenoids are obtained exclusively from fruit and vegetables, the impact of other nutrients on skin carotenoid levels is unknown, as are interactive effects between nutrients. High glycaemic index foods increase oxidative stress through post-prandial glucose elevation. Oxidative stress may reduce the availability of endogenous antioxidants, reduce the prevalence of carotenoids in skin and impair health by predisposing insulin tolerance. Dietary fat may have more complex effects, aiding carotenoid absorption at low levels, while at high levels having adverse consequences due to excess energy intake. Lifestyle factors such as exercise may increase endogenous antioxidant capacity and ameliorate the adverse impact of high glycaemic index foods. Conversely, high body fat may exacerbate the adverse impact of these foods (Vincent et al. 2007).

Aims. We will explore how different aspects of diet (e.g. energy dense foods, fats, fruit and vegetables) affect oxidative balance, carotenoid levels and indices of health. We will examine how individual differences in glucose tolerance/ insulin resistance and lifestyle (exercise, body fat levels) moderate the impact of dietary components on carotenoid levels.

Hypotheses. We predict that (a) fruit and (b) vegetable consumption make independent positive contributions to skin carotenoids; (c) high glycaemic index foods producing high post-prandial blood sugar levels will negatively impact on skin carotenoids; and (d) fats will enhance carotenoid levels at low levels but detract at high levels. Superimposed on these relations (e) habitual exercise will ameliorate and (f) body fat levels will exacerbate the impact of (c) energy dense foods on oxidative stress and carotenoid levels.

Methods. A cross-sectional survey will be prepared for a young adult Caucasian population (n>200). Skin carotenoid levels will be measured with reflectance spectrometry (carotenoids characteristically absorb at 450-500 nm wavelengths). Levels of melanin pigment will also be estimated via spectrometry allowing control for skin lightness. Diet composition will be measured with validated food frequency questionnaires and phone-app image records. Body Mass Index and lifestyle variables (habitual exercise levels, smoking) will be recorded. A subset of participants (n=100) will be followed with measures of blood glucose pre- and post- (8h overnight) fasting; and pre- and 2h post-prandial following a standardised meal. Total antioxidant status and oxidative stress levels will be measured for these individuals. Data analysis will include multiple regression (for linear and quadratic terms) of the impact of the distinct major dietary components on skin carotenoid levels controlling for lifestyle factors. Structural equation modelling will examine the role of blood glucose homeostasis and oxidative capacity in mediating or moderating the dietary effects on skin carotenoids.

As effects of dietary components become clear (years 1-2) we will conduct a longitudinal intervention study in year 3 to investigate interactions between dietary components in increasing skin carotenoids and producing health benefits. For example, we will compare the impact of diets combining high fruit and vegetables with low glycaemic index carbohydrate to control diets, elevating only fruit and vegetables. Outcome variables here will be change in skin carotenoid levels and psychological indices of wellbeing (e.g. self-reports of concentration, mood, health, and sickness frequency) and biomarkers of cardiovascular risk (c-reactive protein, cholesterol).

Training. The student will receive training in behavioural measurements of diet, physiological measurement of biomarkers and research ethics. Statistical training will be provided to support modelling of the pathways between dietary composition, physiological mediators and skin carotenoid levels with the moderating influences of lifestyle. Training on relevant health psychology models of behaviour change (e.g., in diet) will be provided. Ongoing collaborations with Macquarie University, Australia may present the opportunity for a joint international study of carotenoids during the studentship.

Impact. The project will aid understanding of how dietary components interact in their influences on psychological wellbeing and biomarkers of health, including carotenoid skin colour.


  1. Vincent, H.K., Innes, K.E. & Vincent, K.R. (2007) Oxidative stress and potential interventions to reduce oxidative stress in overweight and obesity. Diabetes, Obesity and Metabolism 9, 813–839.
  2. Whitehead, R.D., Ozakinci, G., & Perrett, D.I. (2014). A randomized controlled trial of an appearance-based dietary intervention. Health Psychology, 33, 99-102.
  3. Whitehead, R.D., Re, D., Xiao, D., Ozakinci, G., & Perrett, D.I. (2012). You are what you eat: within-subject increases in fruit and vegetable consumption confer beneficial skin-color changes. PloS one, 7(3), e32988.

The environment

The project will be conducted within the Perception Lab in the School of Psychology & Neuroscience at St Andrews University. Collaborative work will involve health psychology supervised by Dr Gozde Ozakinci in the School of Medicine. The School of Psychology & Neuroscience has been given consistently high ratings in the 2014 REF, 2008 RAE and all previous research assessments. The School has similarly been graded as ‘excellent’ in each teaching review. The Lab is internationally recognised for its work on face perception, computer graphics and attraction. The Perception Lab has seen 4 Case and 16 other PhD students graduate (100% successful completion rate all on time). Career progression has been notable for all postgraduates and post-docs from the Lab.


This research project is eligible for the EASTBIO Doctoral Training Partnership, It is one of a number of projects available at this institution, and is in competition for funding with one or more of these projects. Usually the project which receives the best applicant will be awarded the funding. Some projects, which are funded by charities or by the universities themselves may have more stringent restrictions.

This opportunity is only open to UK nationals (or EU students who have been resident in the UK for 3+ years immediately prior to the programme start date) due to restrictions imposed by the funding body.

How to apply & further information

Please follow the instructions on how to apply at:

For informal enquiries, please contact Dave Perrett,

Application deadline: 5pm on 14th December 2015