The effect of caffeine, green tea and tyrosine on thermogenesis and energy intake.
OBJECTIVE
To investigate the effect of three different food ingredients tyrosine, green tea extract (GTE) and caffeine on resting metabolic rate and haemodynamics, and on ad libitum energy intake (EI) and appetite.


METHODS
Twelve healthy, normal weight men (age: 23.7 +/- 2.6 years, mean +/- s.d.) participated in a four-way crossover, randomized, placebo-controlled, double-blind study. Treatments were administered as tablets of 500 mg GTE, 400 mg tyrosine, 50 mg caffeine, or placebo, and were separated by >3-day washout. The acute thermogenic response was measured in a ventilated hood system for 4 h following ingestion. Blood pressure, heart rate (HR), and subjective appetite sensations were assessed hourly and ad libitum EI 4 h post-dose.


RESULTS
Caffeine induced a thermogenic response of 6% above baseline value (72 +/- 25 kJ per 4 h, mean +/- s.e.) compared to placebo (P<0.0001). The thermogenic responses to GTE and tyrosine were not significantly different from placebo. Tyrosine tended to increase 4-h respiratory quotient by 1% compared to placebo (0.01 +/- 0.005, P=0.05). Ad libitum EI was not significantly different between treatments but was reduced by 8% (-403 +/- 183 kJ), 8% (-400 +/- 335 kJ) and 3% (-151 +/- 377 kJ) compared to placebo after intake of tyrosine, GTE and caffeine, respectively. No significant difference in haemodynamics was observed between treatments.


CONCLUSIONS
Only caffeine was thermogenic in the given dose and caused no haemodynamic side effects. The sample size was probably too small to detect any appetite suppressant properties of the treatments. Further investigations are required.
Belza
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Department of Human Nutrition, Faculty of Life Sciences, University of Copenhagen, Copenhagen, Denmark. anbe@life.ku.dk
Toubro
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Astrup
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D000328:Adult; D001066:Appetite / Q000187:drug effects; D001481:Basal Metabolism / Q000187:drug effects; D001794:Blood Pressure / Q000187:drug effects; D001835:Body Weight / Q000187:drug effects; D002110:Caffeine / Q000494:pharmacology*; D028241:Camellia sinensis; D000697:Central Nervous System Stimulants / Q000494:pharmacology*; D018592:Cross-Over Studies; D004311:Double-Blind Method; D002149:Energy Intake / Q000187:drug effects*; D006339:Heart Rate / Q000187:drug effects; D006801:Humans; D008297:Male; D050177:Overweight / Q000188:drug therapy; D008517:Phytotherapy; D010936:Plant Extracts / Q000494:pharmacology*; D012119:Respiration / Q000187:drug effects; D013662:Tea; D022722:Thermogenesis / Q000187:drug effects*; D014443:Tyrosine / Q000494:pharmacology*; D055815:Young Adult
D000697:Central Nervous System Stimulants; D010936:Plant Extracts; D013662:Tea; D002110:Caffeine; D014443:Tyrosine