Eat chocolate to avoid dying from second heart attack?

By David Liu (davidl@foodconsumer.org)

A new study finds that men and women who had one heart attack, but ate chocolate were three times less likely to die from second heart attack.  

News media reported the study suggesting that eating chocolate may cut the risk of dying from heart attack. But the study results could be misleading.

The study was conducted by Janszky from the Karolinska Institute in Stockholm, Sweden and colleagues and published in the journal of Internal Medicine. The researchers wanted to know if chocolate consumption may affect the risk for heart disease.  

Previous research already suggested that antioxidants like flavanol in cocoa could help lower blood pressure and improved the flow of the blood in the body.

Janszky and colleagues followed up 1,169 men and women aged 45 to 70 who had had at least one heart attack for eight years. At the beginning of the study, participants were questioned about their dietary habits.

They found a link between fatal heart attacks and the amount of chocolate eaten. That is, those who ate more chocolate were less likely to die from heart attack.

The association was still significant even after other factors such as obesity, smoking and alcohol consumption were considered, according to the study.

Readers need to be aware that the study is not a trial, that is, a causal relation between chocolate consumption and risk of death from heart attack was not established, meaning that eating chocolate does not necessarily lead to a lower risk.

A couple of factors may have affected the results. 

First, we do not know what the participants ate during the 8-year follow-up. And second, those who had more serious cardiovascular conditions might have quit eating chocolate prior to enrollment in the study due to the concern about their health status.

In any case, no one should jump eating lots of chocolate as a measure to reduce their risk for heart disease or heart attack. Chocolate should be used as a food largely for pleasure and it should not even be used as a major energy source because of high levels of saturated fat in the food.

As a matter of fact, an Australian trial has demonstrated that eating dark chocolate, which contains large amounts of flavanol, did not lower high blood pressure, a risk factor for cardiovascular morbidity and mortality.

Ried K, Frank O. R. and Stocks N. P. from the University of Adelaide in Australia published the trial results in the July 2009 issue of BMC Complement Alternative Medicine.

Here is how they conducted the trial cited in verbatim from the study Abstract:

Our trial consisted of two phases: a randomised controlled three-group-parallel trial over 12 weeks (phase 1) followed by a crossover of the two active treatment arms over an additional 12-week period (phase 2). Group 1 received a 50 g daily dose of dark chocolate with 70% cocoa containing 750 mg polyphenols, group 2 were allocated one tomato extract capsule containing 15 mg lycopene per day, and group 3 received one placebo capsule daily over 8 weeks followed by a 4-week washout period. In phase 2 the active treatment groups were crossed over to receive the alternative treatment. Median blood pressure, weight, and abdominal circumference were measured 4-weekly, and other characteristics including physical activity, general health, energy, mood, and acceptability of treatment were assessed by questionnaire at 0, 8 and 20 weeks. We analysed changes over time using a linear mixed model, and one time point differences using Kruskal-Wallis, Fisher's-Exact, or t-tests. 

Below is what they found cited in verbatim from the study Abstract:

Thirty-six prehypertensive healthy adult volunteers completed the 6-month trial. Blood pressure changes over time within groups and between groups were not significant and independent of treatment. Weight and other characteristics did not change significantly during the trial. However, a marked difference in acceptability between the two treatment forms (chocolate or capsule) was revealed (p < 0.0001). Half of the participants allocated to the chocolate treatment found it hard to eat 50 g of dark chocolate every day and 20% considered it an unacceptable long-term treatment option, whereas all participants found it easy and acceptable to take a capsule each day for blood pressure. 

The authors concluded that “Our study did not find a blood pressure lowering effect of dark chocolate or tomato extract in a prehypertensive population. Practicability of chocolate as a long-term treatment option may be limited.”