Materials and methods
This paper is a secondary analysis of data from two studies conducted at the Medical Research Council (MRC) Human Nutrition Research (HNR), Cambridge, UK, and MRC Keneba, Keneba, The Gambia. The first study (study 1) was conducted in Cambridge (n = 30) and Keneba (n = 30) in 2005; the second study (study 2) was conducted in Cambridge (n = 30) in 2011 and Keneba (n = 31) in 2010. All procedures were conducted under the same standard operating procedures.
Ethical approval was given by the Cambridge Local Research Ethics Committee and the Gambian Government/MRC Laboratories Joint Ethics Committee. Informed written consent was obtained from all subjects. The research was performed in line with the principles outlined by the Declaration of Helsinki.