Surrey1 The effects of single doses of anhydrous caffeine (250 mg and 500 mg) and placebo on physiological, psychological measures and subjective feelings were studied in a doubleblind, cross-over study in nine healthy subjects who had abstained from caffeine-containing beverages for 24 h before each occasion. 2 Caffeine and caffeine metabolites in plasma and urine were assayed. Peak plasma concentrations were observed at 1 to 2 h with an approximate half-life of 5 h. The concentrations of the metabolite 1,7-dimethylxanthine increased during the 5 h. The major urine metabolite was 1-methyluric acid. 3 The EEG showed a dose-related decrease in log 'theta' power and a decrease in log 'alpha' power. Other dose-related effects were an increase in skin conductance level (sweat-gland activity) and self rating of alertness. Ratings of headache and tiredness were decreased by the caffeine. 4 The study illustrates the complexities of studying a drug which is widely taken and which is often associated with withdrawal effects.

For the past 40 years, the dominant ‘policy’ on cooking energy in the Global South has been to improve the combustion efficiency of biomass fuels. This was said to alleviate the burdens of biomass cooking for three billion people by mitigating emissions, reducing deforestation, alleviating expenditure and collection times on fuels and increasing health outcomes. By 2015, international agencies were openly saying it was a failing policy. The dispersal of improved cookstoves was not keeping up with population growth, increasing urbanisation was leading to denser emissions and evidence suggested health effects of improved stoves were not as expected. A call was made for a new strategy, something other than ‘business as usual’. Conventional wisdom suggests that access to electricity is poor in Sub-Saharan Africa (SSA), that it is too expensive and that weak grids prevent even connected households from cooking. Could a new strategy be built around access to electricity (and gas)? Could bringing modern energy for cooking to the forefront kill two birds with one stone? In 2019, UK Aid announced a multi-million-pound programme on ‘Modern Energy Cooking Services’ (MECS), specifically designed to explore alternative approaches to address cooking energy concerns in the Global South. This paper outlines the rationale behind such a move, and how it will work with existing economies and policies to catalyse a global transition.

1 A large body of research on the demography of caffeine use and its potential health consequences has been undermined by the absence of empirical data on the reliability of retrospective self-reports of caffeine consumption. 2 The principal aim of the present study was to use standard bioanalytic methods to assess the reliability of subjects' self-reported caffeine use. Saliva samples were obtained from 142 first-and second-year medical students and assayed for caffeine and paraxanthine. 3 Self-reported caffeine use was found to be significantly correlated with salivary caffeine (r = 0.31, P < 0.001) and paraxanthine (r = 0.42, P < 0.001), thereby providing qualified support for the use of questionnaires to estimate patterns of caffeine consumption. 4 A secondary aim of the study was to extend previous research concerning the symptomatology of caffeine use by examining the association between caffeine exposure and a variety of measures of somatic and psychological health. Caffeine consumption was reliably associated with the self-reported occurrence of somatic symptoms, but not psychological well-being.

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Forty normal subjects (mean age 36) had their caffeine intake estimated by keeping a diary (n=40) and also by analysing provided samples of tea and coffee (n=28). A test dose of caffeine (500 mg) was given and a series of salivary samples analysed to estimate pharmacokinetic measures of the rate of caffeine metabolism. They then underwent 48 h of placebo substitution using double-blind procedures. A wide range of physiological, psychological and subjective measures were taken on successive days during withdrawal and resumption of caffeine. On withdrawal, 27 subjects reported tiredness and 18 developed headache. Electroencephalograph, skin conductance and blood pressure changes were apparent. Sleep improved on withdrawal but subjects reported feeling less alert and more tired. The higher the usual caffeine intake, the greater the unpleasant feelings on withdrawal and the more marked the reversal of feelings on resumption. The faster the metabolism of caffeine, the less the drop in anxiety during withdrawal and the less its return on resumption. These correlations were, however, rather weak and sporadic.