Thursday, April 1, 2010

Does chocolate lower blood pressure and thus help with heart disease?

Unfortunately this seems to be another example where poor quality research with weak findings is hyped up in the media.

Dr Ray's comments do give you an idea of the statistical jiggery-pokery that all too often is used to try and create the false impression that some significant effect has been observed.

Until there are properly randomised double-blind trials carried out, there really is no evidence of anything.

We'll have to keep on eating chocolate for the only good reason for which there is in fact strong evidence - it tastes good and we like it.

The chocolate wheelbarrow of Meneer Buijsse

I have finally tracked down the latest wisdom on chocolate from Brian Buijsse, who is something of a chocolate evangelist, it would seem. I reproduce the journal abstract below. The only praise I have for it is the last sentence in it.

The article is basically nonsense. They not only found an effect too tiny to support causal inferences but they found it only by comparing extreme quartiles, which is the statistics of desperation. In other words, they arrived at their conclusion by leaving out half of the data! I could say more (correlation is not causation etc.) but I think it is time Meneer Buijsse found another wheelbarrow to push. Buijsse thinks chocolate is good for your heart but the poverty of his results is more consistent with saying that it has no effect at all

Chocolate consumption in relation to blood pressure and risk of cardiovascular disease in German adults

By Brian Buijsse et al.

Aims: To investigate the association of chocolate consumption with measured blood pressure (BP) and the incidence of cardiovascular disease (CVD).

Methods and results: Dietary intake, including chocolate, and BP were assessed at baseline (1994–98) in 19 357 participants (aged 35–65 years) free of myocardial infarction (MI) and stroke and not using antihypertensive medication of the Potsdam arm of the European Prospective Investigation into Cancer and Nutrition. Incident cases of MI (n = 166) and stroke (n = 136) were identified after a mean follow-up of ~8 years. Mean systolic BP was 1.0 mmHg [95% confidence interval (CI) −1.6 to −0.4 mmHg] and mean diastolic BP 0.9 mmHg (95% CI −1.3 to −0.5 mmHg) lower in the top quartile compared with the bottom quartile of chocolate consumption. The relative risk of the combined outcome of MI and stroke for top vs. bottom quartiles was 0.61 (95% CI 0.44–0.87; P linear trend = 0.014). Baseline BP explained 12% of this lower risk (95% CI 3–36%). The inverse association was stronger for stroke than for MI.

Conclusion: Chocolate consumption appears to lower CVD risk, in part through reducing BP. The inverse association may be stronger for stroke than for MI. Further research is needed, in particular randomized trials.

Media article here

Posted via email from Garth's posterous

1 comment:

Maya said...

If you decide to try to incorporate chocolate into your battle against high blood pressure, keep in mind that the chocolate must still have the flavonoids in it for it to have any possible cardiovascular benefits. Most commercial chocolates are so processed they no longer have the flavonoids so be sure to check the label before you buy. Even then the possible benefits will be very small and you only need to eat a little square.
As the authors of this study noted, increasing nitric oxide in the blood stream can be a very effective way to help control your blood pressure. Exercise is a great way to increase nitric oxide. Another fantastic way to lower blood pressure naturally is with an isometric handgrip therapy device called the Zona Plus.