By Seema Gupta, MD, MSPH

Clinical Assistant Professor, Department of Family and Community Health, Joan C. Edwards School of Medicine,
Marshall University, Huntington, WV

Dr. Gupta reports no financial relationships relevant to this field of study.

SYNOPSIS: Chocolate consumption may improve liver enzymes and protect against insulin resistance.

SOURCE: Alkerwi A, Sauvageot N, Crichton GE, et al. Daily chocolate consumption is inversely associated with insulin resistance and liver enzymes in the Observation of Cardiovascular Risk Factors in Luxembourg study. Br J Nutr 2016 May;115:1661-1668.

Cardiovascular disease (CVD) is the leading global cause of death. In the United States, CVD is the cause of more deaths than cancer, chronic lower respiratory diseases, and accidents combined, accounting for almost one out of every three deaths. Modifiable risk factors for CVD include metabolic disorders such as obesity, diabetes, hypertension, and hypercholesterolemia. Previous population-based studies clearly have demonstrated that compared with non-diabetics, patients with type 2 diabetes have a higher cardiovascular morbidity and mortality as well as increased all-cause mortality.1 However, there is evidence suggesting that even in non-diabetic individuals, hyperinsulinemia is associated with an increased cardiovascular risk and a number of other conditions, including hypertension, dyslipidemia, and a central adiposity.2 Dietary intake is one of the key lifestyle factors involved in the prevention and control of these cardiometabolic disorders.

Cocoa products containing polyphenols have shown encouraging potential in the prevention of cardiometabolic disorders.3 Recent studies suggest chocolate consumption positively influences human health, with antioxidant, antihypertensive, anti-inflammatory, antiatherogenic, and antithrombotic effects as well as an influence on insulin sensitivity, vascular endothelial function, and activation of nitric oxide.4 Researchers believe such health benefits might be linked, at least in part, to plant-derived polyphenols and their flavonoids subclasses. Interestingly, evidence suggests cocoa, especially dark chocolate, is more beneficial to health than teas and red wine in terms of its antioxidant capacity due to higher concentrations of flavonoids per serving.5 Previously, a small 15-day dark chocolate consumption study demonstrated a lowering of blood pressure and increased insulin sensitivity in glucose-intolerant, hypertensive subjects.6

Alkerwi et al hypothesized that chocolate consumption may produce a beneficial effect on insulin sensitivity and liver enzymes. Researchers analyzed data from 1,153 patients, aged 18 to 69 years, enrolled in the Observation of Cardiovascular Risk in Luxembourg study, the first nationwide survey on heart disease risk factors. Chocolate consumption information was obtained from a semiquantitative, self-administered questionnaire. Researchers used blood glucose and insulin levels for the homoeostasis model assessment of insulin resistance (HOMA-IR). Hepatic biomarkers such as serum gamma-glutamyl transpeptidase (GGT), serum aspartate transaminase (AST), and serum alanine transaminase (ALT) were assessed using standard laboratory assays. Subjects taking antidiabetic medications were excluded, and results were adjusted for age, sex, education, lifestyle, and dietary confounding factors, including intakes of fruits and vegetables, alcohol, polyphenol-rich coffee, and tea. Researchers found that daily consumption of 100 grams of chocolate was associated with a reduction of HOMA-IR by 0.16 (P = 0.004), of serum insulin levels by 0.16 μg/l (P = 0.003), and of liver enzymes (GGT, ALT) by > 0.10 mg/L (P = 0.009 and 0.004, respectively). Researchers did not detect any statistically significant associations of fasting plasma glucose or HbA1c with chocolate consumption.

The authors concluded that there is an independent inverse relationship between daily chocolate consumption and levels of insulin, HOMA-IR, and liver enzymes in adults, suggesting chocolate consumption may protect against insulin resistance and improve liver enzymes.

COMMENTARY

This is great news for chocoholics. Those who aren’t should strongly consider these results, as this research adds to the growing body of evidence that daily consumption of approximately 100 grams of chocolate seems to lower insulin resistance while improving liver enzymes. Research into the health effects of cocoa has received significant attention over the past few years. However, it is important to note that while this study has generated critical insight into the issue, the limitations of demonstrating a cause and effect relationship rest in its cross-sectional design. Further studies with well-designed, randomized, controlled trials are needed to confirm these findings as well as better understand the mechanisms behind the components in chocolate that provide benefit with regard to insulin resistance and cardiometabolic disorders.

Diseases associated with modifiable risk factors are the leading cause of illness and death in the United States. Research consistently demonstrates that a healthy diet and physical activity are associated with benefits in significant health outcomes, including reductions in CVD and all-cause mortality. However, despite this convincing evidence, adults continue ignoring these healthy diet and physical activity recommendations.7 This study provides interesting insight into the benefits of daily chocolate consumption among apparently healthy adults, a recommendation that may be easier to follow. I often write my patients prescriptions for exercise and more vegetable and fruit consumption. While I won’t be writing any prescriptions for chocolate anytime soon, I surely won’t tell patients not to eat it either. The best bet is to stick with dark chocolate in moderation.

REFERENCES

  1. Gu K, Cowie CC, Harris MI. Diabetes and decline in heart disease mortality in US adults. JAMA 1999;281:1291-1297.
  2. Balkau B, Eschwège E. Insulin resistance: An independent risk factor for cardiovascular disease? Diabetes Obes Metab 1999;1(Suppl 1):S23-31.
  3. Corti R, Flammer AJ, Hollenberg NK, et al. Cocoa and cardiovascular health. Circulation 2009;119:1433-1441.
  4. Buitrago-Lopez A1, Sanderson J, Johnson L, et al. Chocolate consumption and cardiometabolic disorders: Systematic review and meta-analysis. BMJ 2011;343:d4488.
  5. Lee KW, Kim YJ, Lee HJ, et al. Cocoa has more phenolic phytochemicals and a higher antioxidant capacity than teas and red wine. J Agric Food Chem 2003;51:7292-7295.
  6. Grassi D, Desideri G, Necozione S, et al. Blood pressure is reduced and insulin sensitivity increased in glucose-intolerant, hypertensive subjects after 15 days of consuming high-polyphenol dark chocolate. J Nutr 2008;138:1671-1676.
  7. Lin JS, O’Connor EA, Evans CV, et al. Behavioral counseling to promote a healthy lifestyle for cardiovascular disease prevention in persons with cardiovascular risk factors: An updated systematic evidence review for the U.S. Preventive Services Task Force [Internet]. Rockville (MD): Agency for Healthcare Research and Quality (US); 2014. Report No.: 13-05179-EF-1.