Beneficial Cardiovascular Effects of Cocoa Flavanols Are Enhanced by Methylxanthines

  • Cocoa (Theobroma cacao, Malvaceae)
  • Flavanols
  • Methylxanthines
  • Cardiovascular Function

Cocoa (Theobroma cacao, Malvaceae) flavanols (CFS) have been shown to exhibit beneficial cardiovascular effects. The authors suggest that other compounds in foods that contain flavanols, such as methylxanthines, could also help improve vascular functions. In cocoa, the main methylxanthines are theobromine and caffeine. Conducting 4 randomized, double-masked, controlled studies, the authors investigated the potential role of methylxanthines in modulating the cardiovascular effects of CFS in humans.

Between February 2011 and December 2014, the authors recruited healthy young men aged 25 to 30 years to participate in the 4 studies. In all studies, the study days were separated by at least 1 week to avoid any carryover effects. Baseline characteristics were similar among the 47 subjects recruited for the studies. No adverse effects were reported during any of the studies.

The drinks used in studies 1-3 were fruit-flavored nondairy drinks containing CFS (0-820 mg) and methylxanthines (0-220 mg), individually or combined. The drink in study 4 contained food-grade epicatechin isolated from cocoa (Mars Inc.; McLean, Virginia), food-grade theobromine (AHD International LLC; Atlanta, Georgia), and caffeine (Perrigo; Allegan, Michigan) added to 1% fat milk.

Study 1, the main proof-of-concept study, examined the interactions of CFS and methylxanthines in modulating cardiovascular function, including flow-mediated vasodilation (FMD), arterial stiffness, blood pressure (BP), circulating angiogenic cells (CACs), and brachial pulse wave velocity (bPWV). The acute, 3-arm, single-center, randomized, double-masked, crossover study with 12 subjects was conducted at Heinrich-Heine-University Düsseldorf (HHUD) in Düsseldorf, Germany. The test drinks consumed by the subjects provided either 820 mg CFs, 125 mg cocoa methylxanthines, or both CFS and methylxanthines. On 3 study days, cardiovascular function tests were conducted at baseline, before consumption of the drink, and 2 hours after intake.

The authors report that ingestion of both the drink containing CFS only and the drink containing CFS and methylxanthines resulted in a significant increase in FMD 2 hours after intake compared with baseline (P<0.05). The FMD increase was more significant after consumption of the drink containing both CFS and methylxanthines than after consumption of the drink containing only CFS (P<0.05). No changes in FMD were observed after consumption of the drink containing methylxanthines only. The CF-only drink resulted in significant positive changes in CACs (P<0.001) and bPWV (P=0.011), but no changes in diastolic BP. Positive changes in CACs (P<0.001) and decreases in bPWV (P=0.011) and diastolic BP (P=0.011) were seen after consumption of the drink containing CFS and methylxanthines, and those changes were greater than those observed after consumption of the CF-only drink. “In summary, the intake of CFS acutely improved multiple functional markers of vascular health, and, notably, the co-ingestions of CFs with methylxanthines enhanced the effect of CFS on the vascular function biomarkers investigated … .,” write the authors.

Study 2, which assessed the effect of methylxanthines consumed with CFS in varying amounts, was a single-center (HHUD), randomized, double-masked, crossover study. Twenty-four subjects were randomly assigned to 4 groups of 6 each. The subjects consumed test drinks during 10 (groups 1 and 2) or 8 (groups 3 and 4) study visits and underwent FMD measurements at baseline and 2 hours after ingestion of the drink.

The groups were assigned drinks as follows:

  • Group 1―increasing amounts of CFS (0, 102, 205, 410, and 820 mg)
  • Group 2―increasing amounts of CFS as in group 1 along with 122 mg methylxanthines
  • Group 3―increasing amounts of methylxanthines (0, 61, 122, and 244 mg)
  • Group 4―increasing amounts of methylxanthines as in group 3 along with 820 mg CFS.

The authors report the 6 subjects in group 1 showed a significant increase in FMD at 2 hours after intake of >105 mg CFS compared with baseline (P<0.01). In the 6 subjects in group 2 who consumed drinks with increasing amounts of CFS along with methylxanthines, a CF intake-dependent increase in FMD was seen after 2 hours. No changes in FMD were seen in the 6 subjects in group 3 who consumed methylxanthines only. In group 4, the consumption of CFS and increasing amounts of methylxanthines resulted in a methylxanthine intake-dependent increase in FMD.

In study 3, the authors investigated how methylxanthines might modulate the plasma and urinary levels of structurally related (−)-epicatechin metabolites (SREMs) and the effect on FMD. Conducted at HHUD, the randomized, double-masked, 2-arm, crossover study included 5 subjects who consumed test drinks and provided blood and 0- to 24-hour urine samples. Levels of SREMs were assessed at baseline and hourly for 5 hours after consumption of the following test drinks: 1 containing 820 mg CFS (including 112 mg epicatechin) and 1 containing the same amount of CFS plus 122 mg methylxanthines (including 111 mg theobromine and 11 mg caffeine).

The authors report that the consumption of both drinks significantly increased the FMD response (P<0.05), with the greatest response observed 2 hours after consumption. Consumption of the drink with both CFS and methylxanthines resulted in a significantly higher peak plasma concentration of SREMs when compared with intake of the CF-only drink (P<0.05). Urinary levels of SREMs were similar in all subjects at baseline and 2 hours after consumption of the test drinks.

The effects of pure theobromine and caffeine consumed with epicatechin on plasma and urinary levels of SREMs were examined in study 4, a single-center, randomized, double-masked, crossover study conducted at the University of California, Davis. Six subjects consumed 75 mg epicatechin either with or without 400 mg theobromine and 26 mg caffeine on 2 different days. Blood samples were drawn at baseline and at 1, 2, and 4 hours after consumption of the drinks. Baseline and 24-hour urine samples were collected.

The authors report the consumption of both drinks significantly increased peak plasma concentration of SREMs (P<0.05), with the greatest increases observed at 2 hours after intake. Those increases were greater after consumption of the drink containing theobromine, caffeine, and epicatechin than after the intake of the drink containing only epicatechin (P<0.05).

“The intake of test drinks containing CFS either with or without methylxanthines resulted in acute improvements of established functional cardiovascular biomarkers in healthy adults. … [T]he intake of methylxanthines alone did not mediate acute changes in the biomarkers assessed … .,” state the authors, suggesting that “the amounts of methylxanthines administered herein or the matrix in which they were consumed were not conducive for mediating the effects on the observed parameters.”

“[O]ur results demonstrate a significant interaction between cocoa methylxanthines and CFS in which methylxanthines, likely by affecting CF absorption, enhance the vascular effects commonly ascribed to CF intake with cocoa,” conclude the authors.

Mars Inc. provided financial support and the test drinks used for these studies. Two of the authors (Ottaviani and Schroeter) are employed by Mars Inc., and 4 of the authors (Spencer, Crozier, Kelm, and Heiss) received unrestricted research grants from Mars Inc.