Time for tea: mood, blood pressure and cognitive performance effects of caffeine and theanine administered alone and together
Although both contain behaviourally significant concentrations of caffeine, tea is commonly perceived to be a less stimulating drink than coffee. At least part of the explanation for this may be that theanine, which is present in tea but not coffee, has relaxing effects. There is also some evidence that theanine affects cognitive performance, and it has been found to reduce blood pressure in hypertensive rats.
To study the subjective, behavioural and blood pressure effects of theanine and caffeine administered alone and together, in doses relevant to the daily tea consumption of regular tea drinkers.
Materials and methods
In a randomised, double-blind, placebo-controlled study, healthy adult participants (n = 48) received either 250-mg caffeine, 200-mg theanine, both or neither of these. They completed ratings of mood, including anxiety, and alertness, and had their blood pressure measured before and starting 40 min after drug administration. Anxiety was also assessed using a visual probe task.
Caffeine increased self-rated alertness and jitteriness and blood pressure. Theanine antagonised the effect of caffeine on blood pressure but did not significantly affect jitteriness, alertness or other aspects of mood. Theanine also slowed overall reaction time on the visual probe task.
Theanine is a physiologically and behaviourally active compound and, while it is unclear how its effects might explain perceived differences between tea and coffee, evidence suggests that it may be useful for reducing raised blood pressure.
KeywordsCaffeine Theanine Tea Coffee Blood pressure Mood Alertness Anxiety Cognition
- Cornelis MC, El-Sohemy A (2005) Coffee, caffeine, and coronary heart disease. Curr Opin Lipidology 18:13–19Google Scholar
- Dubick MA, Omaye ST (2006) Grape wine and tea polyphenols in the modulation of atherosclerosis and heart disease. In: Wildman REC (ed) Handbook of nutraceuticals and functional foods, second edition. Taylor and Francis, London, pp 101–130Google Scholar
- Food Standards Agency (2004) Survey of caffeine levels in hot beverages. Food Survey Information Sheet 53/04. http://www.food.gov.uk/multimedia/pdfs/fsis5304.pdf
- Haskell CF, Kenedy DO, Milne AL, Wesnes KA, Scholey AB (2005) Behavioural effects of caffeine and theanine alone and in combination. J Psychophamacol 19(suppl):A45Google Scholar
- Heatherley SV, Mullings EL, Tidbury MA, Rogers PJ (2006a) Caffeine consumption among a sample of UK adults. Appetite 47:266Google Scholar
- Heatherley SV, Mullings EL, Tidbury MA, Rogers PJ (2006b) The Dietary Caffeine and Health Study: administration of a large postal survey in Bristol. Appetite 47:266Google Scholar
- Howell DC (1997) Statistical methods for psychology. Duxbury Press, Belmont, CAGoogle Scholar
- Hughes RN (1996) Drugs which induce anxiety: caffeine. New Zeal J Psychol 25:36–42Google Scholar
- James JE, Rogers PJ (2005) Effects of caffeine on performance and mood: withdrawal reversal is the most plausible explanation. Psychopharmacology 182:1–8Google Scholar
- Lovibond SH, Lovibond PF (1995) Manual for the Depression Anxiety and Stress Scales. Psychology Foundation of Australia Inc., Sydney, AustraliaGoogle Scholar
- MacLeod C, Mathews A (1988) Anxiety and the allocation of attention to threat. Q J Exp Psychol 40:653–670Google Scholar
- Nantz MP, Rowe CA, Azeredo A, Marano LE, Bukowski JF, Percival SS (2007) A standardized green tea formula lowers serum amyloid alpha and blood pressure. FASEB J 21:225.3Google Scholar
- Rogers PJ, Dernoncourt C (1998) Regular caffeine consumption: a balance of adverse and beneficial effects for mood and psychomotor performance. Pharmacol Biochem Behav 59:1039–1045Google Scholar
- Spielberger CD (1991) State-Trait Anger Expression Inventory: professional manual. Psychological Assessment Resources Inc., Odessa, FLGoogle Scholar
- Umezara K, Kobayashi K, Muramoto K, Kawahara M, Mitzutani A, Kakuda T, Kuroda Y (1995) Theanine, a glutamate analog, stimulates NMDA-receptors but suppresses excitatory effect of caffeine on cortical neurons. Society for Neuroscience 21:835(abstract)Google Scholar