Short-term administration of dark chocolate is followed by a significant increase in insulin sensitivity and a decrease in blood pressure in healthy persons

Am J Clin Nutr. 2005 Mar;81(3):611-4. doi: 10.1093/ajcn/81.3.611.


Background: Numerous studies indicate that flavanols may exert significant vascular protection because of their antioxidant properties and increased nitric oxide bioavailability. In turn, nitric oxide bioavailability deeply influences insulin-stimulated glucose uptake and vascular tone. Thus, flavanols may also exert positive metabolic and pressor effects.

Objective: The objective was to compare the effects of either dark or white chocolate bars on blood pressure and glucose and insulin responses to an oral-glucose-tolerance test in healthy subjects.

Design: After a 7-d cocoa-free run-in phase, 15 healthy subjects were randomly assigned to receive for 15 d either 100 g dark chocolate bars, which contained approximately 500 mg polyphenols, or 90 g white chocolate bars, which presumably contained no polyphenols. Successively, subjects entered a further cocoa-free washout phase of 7 d and then were crossed over to the other condition. Oral-glucose-tolerance tests were performed at the end of each period to calculate the homeostasis model assessment of insulin resistance (HOMA-IR) and the quantitative insulin sensitivity check index (QUICKI); blood pressure was measured daily.

Results: HOMA-IR was significantly lower after dark than after white chocolate ingestion (0.94 +/- 0.42 compared with 1.72 +/- 0.62; P < 0.001), and QUICKI was significantly higher after dark than after white chocolate ingestion (0.398 +/- 0.039 compared with 0356 +/- 0.023; P = 0.001). Although within normal values, systolic blood pressure was lower after dark than after white chocolate ingestion (107.5 +/- 8.6 compared with 113.9 +/- 8.4 mm Hg; P < 0.05).

Conclusion: Dark, but not white, chocolate decreases blood pressure and improves insulin sensitivity in healthy persons.

Publication types

  • Clinical Trial
  • Randomized Controlled Trial
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Analysis of Variance
  • Area Under Curve
  • Blood Glucose / analysis
  • Blood Glucose / drug effects*
  • Blood Pressure / drug effects*
  • Cacao / chemistry*
  • Candy*
  • Cross-Over Studies
  • Dose-Response Relationship, Drug
  • Female
  • Flavonoids / administration & dosage*
  • Flavonoids / pharmacology
  • Flavonols / administration & dosage
  • Flavonols / pharmacology
  • Glucose Tolerance Test
  • Homeostasis
  • Humans
  • Insulin / metabolism*
  • Insulin Resistance
  • Male
  • Phenols / administration & dosage*
  • Phenols / pharmacology
  • Polyphenols


  • Blood Glucose
  • Flavonoids
  • Flavonols
  • Insulin
  • Phenols
  • Polyphenols