Theobromine

At extreme doses, theobromine contributes to cardiovascular stimulation. A case report documented sinus tachycardia in a patient consuming approximately 180 g of dark chocolate nightly for 2 weeks, representing cumulative methylxanthine load. Individuals with pre-existing tachyarrhythmias or cardiac conduction disorders should avoid high-dose theobromine supplementation.

A randomized controlled trial demonstrated that theobromine at 500 mg/day for 4 weeks produced unfavorable postprandial glucose and insulin responses without affecting fasting lipid levels. Individuals with impaired glucose tolerance or diabetes should exercise caution with high-dose theobromine supplementation (>400 mg/day). Dietary chocolate consumption at normal levels is unlikely to reach this threshold.

Theobromine is teratogenic in animal studies at high doses — rats showed delayed osteogenesis at >50× typical human consumption, and rabbits showed developmental variations at 125–200 mg/kg/day by gavage. No adequate controlled human data exist. Dietary chocolate at normal consumption levels has not been associated with adverse developmental outcomes. High-dose theobromine supplementation during pregnancy should be avoided as a precaution, consistent with caffeine pregnancy guidance (limit 200–300 mg/day).

CYP1A2 contributes partially to theobromine metabolism. Potent CYP1A2 inhibitors — including fluvoxamine, ciprofloxacin, and cimetidine — may decrease theobromine clearance and increase plasma concentrations. No clinical drug interaction studies specific to theobromine have been published; this interaction is inferred from metabolic enzyme involvement (Gates & Miners 1999). Individuals on potent CYP1A2 inhibitors should be aware of potentially prolonged theobromine effects at supplement doses.