Black tea improves attention and self-reported alertness.

Tea has previously been demonstrated to better help sustain alertness throughout the day in open-label studies. We investigated whether tea improves attention and self-reported alertness in two double-blind, randomised, placebo-controlled, crossover studies. Participants received black tea (made from commercially available tea bags) in one condition and placebo tea (hot water with food colours and flavours) similar in taste and appearance to real tea in the other condition. Attention was measured objectively with attention tests (the switch task and the intersensory-attention test) and subjectively with a self-report questionnaire (Bond-Lader visual analogue scales). In both studies, black tea significantly enhanced accuracy on the switch task (study 1 p<.002, study 2 p=.007) and self-reported alertness on the Bond-Lader questionnaire (study 1 p<.001, study 2 p=.021). The first study also demonstrated better auditory (p<.001) and visual (p=.030) intersensory attention after black tea compared to placebo. Simulation of theanine and caffeine plasma time-concentration curves indicated higher levels in the first study compared to the second, which supports the finding that tea effects on attention were strongest in the first study. Being the second most widely consumed beverage in the world after water, tea is a relevant contributor to our daily cognitive functioning.

The combination of L-theanine and caffeine improves cognitive performance and increases subjective alertness.

The non-proteinic amino acid L-theanine and caffeine, a methylxanthine derivative, are naturally occurring ingredients in tea. The present study investigated the effect of a combination of 97 mg L-theanine and 40 mg caffeine as compared to placebo treatment on cognitive performance, alertness, blood pressure, and heart rate in a sample of young adults (n = 44). Cognitive performance, self-reported mood, blood pressure, and heart rate were measured before L-theanine and caffeine administration (i.e. at baseline) and 20 min and 70 min thereafter. The combination of moderate levels of L-theanine and caffeine significantly improved accuracy during task switching and self-reported alertness (both P < 0.01) and reduced self-reported tiredness (P < 0.05). There were no significant effects on other cognitive tasks, such as visual search, choice reaction times, or mental rotation. The present results suggest that 97 mg of L-theanine in combination with 40 mg of caffeine helps to focus attention during a demanding cognitive task.

A critical analysis of the rabbit eye irritation test variability and its impact on the validation of alternative methods.

Determining the validity of alternative methods as replacements for the rabbit eye irritation tests is a goal of the scientific, regulatory and political communities and is being evaluated in several studies. The results from the Draize rabbit eye test are used as a standard against which to compare the performance of the in vitro methods. However, the quantitative performance of the modern Draize eye test is unknown. This paper is a review of the findings of a previous study to estimate the historical variability and a comparison with more contemporary data in order to estimate the performance of the modern methods. The question of whether it is practical to obtain an accurate description of in vivo variability of the modern Draize test is considered by calculating the size of the interlaboratory study that would be required to determine whether variability had changed since 1971. The impact that in vivo variability has on the validation of alternative methods is then discussed. The authors conclude that validation studies have a greater chance of success if the alternative methods are soundly based on mechanisms of toxicity operating in vivo, the Draize data are well defined with regard to their variability, the goals of the study are realistic and the customers of the study are in broad agreement with the study design and the in vivo data used as the reference test set.