For the past 10 years, Alan's primary research focus has been nutrition in older age, and he has conducted a series of trials to determine the effectiveness of nutrition interventions for the maintenance of health and function in later life. Alan is the principal investigator of the OPAL study which is a randomised controlled trial designed to determine the effect of daily supplementation with n-3 long-chain polyunsaturated fatty acids on cognitive and retinal function in older people, and of the OPEN study which is a randomised controlled trial designed to determine the effect of daily vitamin B12 supplementation on neurocognitive function in older people. He is a co-investigator in a cost-effectiveness evaluation of the national programme of nutritional supplementation in older people in Chile (CENEX-Chile), and worked on a project to defined the minimum income for healthy living in older people in the UK. Alan also led the team reviewing the available evidence on the nutrient composition and nutrition-related health benefits of organic foods, and conducted a landscape analysis on advocacy for undernutrition in Europe.

An increasing focus of Alan's research is the interaction between the environment, agriculture, nutrition and health and Alan is part of the inter-disciplinary team behind the Leverhulme Centre for Integrative Research on Agriculture and Health (LCIRAH). The Centre conducts inter-sectoral research on: poverty and development; globalisation and food quality; sustainability, environment and climate change; food-borne and zoonotic diseases; and common metrics for agricultural research and evaluation. In partnership with other LCIRAH academics, Alan leads the intervention research pillar of the DFID-supported research consortium Leveraging Agriculture for Nutrition in South Asia (LANSA).

Alan also leads Wellcome Trust-supported Our Planet, Our Health projects on sustainble and healthy diets in India, and on the impact of multiple environmental stressors on food and nutrition security.