Previous randomized clinical trials have shown that drinking chocolate, especially chocolate enriched with flavonoids in dark chocolate, lowers systolic and diastolic blood pressure levels and generally has a beneficial effect on the state of the cardiovascular system. In addition, in observational studies, an inverse relationship was found between the use of chocolate and the risk of developing cardiovascular disease. The purpose of this prospective cohort study was to identify the relationship between chocolate consumption and the likelihood of heart failure.

The study involved 31,823 women aged 48 to 83 years included in the Swedish mammography cohort, who did not have diabetes at the start of the study and had no history of heart failure or myocardial infarction. The Swedish mammographic cohort is made up of women born between 1914 and 1948, living in two districts in central Sweden. All study participants completed questionnaires, which included questions about health status, lifestyle and also about the frequency of food. In addition, an analysis was made of other indicators that may contribute to the development of heart failure (use of other food products, BMI, level of physical activity, especially family history, etc.).

In order to assess the diet, the questionnaire submitted included food and drink (96 points in total), for each of which it was necessary to indicate the frequency of consumption in the previous year. For chocolate, 8 categories were graded from lack of chocolate to 3 or more times a day. General physical activity was assessed in the following categories: occupation, regular exercise or sedentary lifestyle. Women who consumed a large number of calories and did not complete more than half the questionnaire, with a history of heart failure, MI, diabetes mellitus and cancer pathology, were excluded from the study.

The women were followed from January 1998 to December 31, 2006, taking into account the frequency of hospitalizations and deaths due to heart failure based on data from the Swedish register of causes of hospitalization and death.

The average age of the participants was 62, BMI - 25 kg / m²; more than half of the respondents never smoked, a quarter smoked in the past and another quarter of the respondents smoked at the time of the study. 70% of the participants were single, half of the participants took hormonal drugs in the postmenopausal period.

During nine years of medical observation, the morbidity and mortality due to the development of heart failure were 15.1 per 10,000 person-years. In 419 women, heart failure was recorded, of which 379 were hospitalized, 40 died. Compared to irregular chocolate consumption, the multivariate odds ratio for developing heart failure was 0.74 (95% CI, 0.58-0.95) for women who consumed one to three servings of chocolate per month , 0.68 (95% CI, 0.50-0.93) for those who consumed one to two servings per week, 1.09 (95% CI, 0.74-1.62) for those who consumed 3 to 6 servings per week, and 1.23 (95% CI, 0.73-2.08) for those who consumed more than one serving per day (p = 0.0005 for quadratic dependence). The adjusted risk of developing heart failure over a nine-year follow-up period decreased by 26% among women who consumed one to three servings of chocolate per month, and by 32% among those who consumed one or two servings per month week.

These chocolate effects are determined by its type. Flavonoids, which mainly cause positive cardiovascular effects, are concentrated in dry cocoa residues (so-called "pure" chocolate which does not contain cocoa butter). Therefore, the higher the cocoa concentration, the more pronounced the positive effect of consuming chocolate. Although the chocolate used in Sweden is mainly milk, it fully complies with European recommendations, since the amount of cocoa it contains is around 30%. Compared to some varieties of dark chocolate used in the United States, a pure cocoa residue of up to 15% is allowed; Swedish chocolate is much healthier.

At the same time, the problem remains the high calorie content of chocolate due to sugar and fat, as well as the fact that chocolate displaces vegetables and fruits from the diet, which also have a favorable cardio and vasoprotective effect. The question of the positive effect of chocolate in men also remains open in this study. According to data in the literature, the effect of chocolate on blood pressure and other indicators in women and men is similar. Therefore, there is no serious reason to believe that the effects of chocolate will in any way differ in men. However, for greater certainty, it would not be useless, according to the researchers, to conduct a similar study in humans.

Thus, in the population studied, regular consumption of chocolate in moderation contributed to a decrease in the frequency of hospitalizations and deaths due to the development of heart failure. However, with more than one serving of chocolate per day, no similar protective effect was obtained.