Benefits
Blood Pressure: A Brief Acute Dip, No Lasting Drop
A single 700 mg dose lowered blood pressure at 1 hour in 24 healthy women, and 4 weeks at 500 mg/day slightly lowered central augmentation index, a measure of arterial wave reflection. Daily use did not lower resting blood pressure: 12 weeks at 450 mg/day changed neither systolic nor diastolic pressure, and a cocoa drink supplying 979 mg/day for 3 weeks raised 24-hour systolic pressure by 3.2 mmHg versus placebo.
Alertness and Mood Compared With Caffeine
Theobromine is cleared more slowly than caffeine but did not raise alertness the way caffeine did in three controlled trials. In 24 women, caffeine 120 mg raised alertness while theobromine 700 mg did not and lowered calmness at 3 hours. In 24 men, 100 to 400 mg did not consistently change mood or vigilance. In 80 adults, 250 mg had limited effects while higher doses worsened mood and raised heart rate.
HDL Cholesterol: Raised in Two Trials, Not in a Third
Two randomized trials found an HDL rise: 850 mg/day for 4 weeks raised HDL by 0.16 mmol/L in 152 adults aged 40 to 70, and 450 mg/day for 12 weeks with a low-calorie diet raised it by 1.72 mg/dL in 72 adults with metabolic syndrome. A 4-week crossover at 500 mg/day in 44 adults with low HDL found only a trend and no change in HDL subclasses. LDL fell in both 4-week trials but not in the 12-week trial.
Weaker Stimulant Signature Than Caffeine, But Not Calming
Theobromine shows a smaller stimulant effect than caffeine in controlled trials, but that is not the same as a calming effect. The one trial that measured calmness found 700 mg reduced it at 3 hours, and the 80-person dose-ranging trial found worse mood at the higher doses, so the data do not support describing it as a smoother lift than caffeine.
Mechanism of action
Adenosine Receptor Binding
Like caffeine, theobromine crosses into the brain and binds adenosine receptors. It enters the brain less readily than caffeine and is a weaker phosphodiesterase inhibitor, which fits its much smaller effect on alertness in trials.
Effects on Artery Diameter and Wave Reflection
In a 4-week trial at 500 mg/day, theobromine widened the brachial artery after a meal and lowered augmentation index, but did not improve endothelial function measured by flow-mediated dilation. Resting blood pressure did not fall over 3 to 12 weeks of daily use.
Airway and Cough Effects Not Shown in a Trial
Theobromine was tested as a cough product: in 289 adults with persistent cough, twice-daily use for 14 days did not significantly improve the cough quality-of-life endpoint, cough severity or pulmonary function compared with placebo.
Clinical trials
Randomized crossover study comparing theobromine 700 mg, caffeine 120 mg, the combination, and placebo on mood, psychomotor performance and blood pressure measured up to 3 hours post-dose. (Mitchell et al. 2011, Physiol Behav)
24 healthy female adults, randomized crossover design.
Theobromine 700 mg lowered blood pressure relative to placebo at 1 hour and decreased self-reported calmness at 3 hours. Caffeine, not theobromine, raised self-reported alertness at 1, 2 and 3 hours and contentedness at 1 and 2 hours, and caffeine raised blood pressure at 1 hour. There was no treatment effect on Digit Symbol Substitution Test performance in any arm. Combined theobromine and caffeine matched caffeine's mood effects but lost the blood-pressure-lowering signal, suggesting partly independent peripheral and central mechanisms.
Within-subjects placebo-controlled study of oral theobromine 250, 500 and 1,000 mg with caffeine 200 mg as active control, with subjective and cardiovascular measures over several hours. (Baggott et al. 2013, Psychopharmacology (Berl))
80 healthy adults, within-subjects placebo-controlled design.
Caffeine produced expected alertness and cardiovascular changes. Theobromine effects were dose-dependent: limited subjective effects at 250 mg and negative mood effects at the higher doses, not only the top dose, and heart rate rose as the dose rose. The data clarify that theobromine has a different and milder psychopharmacological profile than caffeine.
Two-center, double-blind, randomized, placebo-controlled factorial trial of a daily drink with cocoa, 850 mg pure theobromine, both, or neither for 4 weeks. (Neufingerl et al. 2013, Am J Clin Nutr)
152 healthy men and women aged 40 to 70.
Theobromine raised HDL cholesterol by 0.16 mmol/L and apolipoprotein A-I and lowered apolipoprotein B and LDL cholesterol. Cocoa alone had no significant effect. The trial was run by Unilever researchers.
Double-blind, placebo-controlled 3-period crossover trial of dairy drinks with placebo, cocoa with 106 mg theobromine, or cocoa enriched to 979 mg theobromine, each for 3 weeks. (van den Bogaard et al. 2010, Hypertension)
42 adults aged about 62 with office blood pressure of 130 to 159 / 85 to 99 mmHg.
The primary outcome, 24-hour ambulatory systolic blood pressure, was 3.2 mmHg higher with theobromine-enriched cocoa than placebo. Two hours after a drink, central systolic pressure was 4.3 mmHg lower. The natural-dose cocoa changed neither.