CHOCOLATE AND CARDIOVASCULAR DISEASE
With Easter approaching, you might be wondering about the impact of enjoying chocolate on your health.
Many studies have been published looking at the health effects of
chocolate, but the findings have been inconsistent. With the aim of
better understanding the association between chocolate intake and
chronic disease risk, a group of European researchers recently published
a systematic review and meta-analysis of relevant studies. They
combined the findings of 27 studies, including more than 1 million
participants, looking at the association between all-cause mortality,
coronary heart disease, colorectal cancer, heart failure, hypertension,
stroke and type 2 diabetes.
The researchers found a
small inverse relationship between chocolate consumption and risk of
coronary heart disease and stroke. For each 10g/day increase in intake,
the risk of coronary heart disease was reduced by 4% and stroke by 10%.
No relationship was seen for the other chronic diseases or all-cause
mortality (death).
However, they also point out that
limitations with many of the studies mean that the credibility of
evidence for a relationship between chocolate intake and chronic disease
risk is low. One important factor is the failure of studies to
distinguish between intakes of dark and milk chocolate.
Chocolate
has been found to contain a range of antioxidants, in particular
flavanols, which are also found in fruits, vegetables, tea and red wine,
and which may help in the prevention of some chronic diseases. In fact,
cocoa has more flavanols than other sources such as wine and green tea.
There is some evidence that cocoa flavanols might help to protect
against heart disease and stroke by lowering blood pressure and
improving the health of blood vessels - reducing inflammation,
increasing blood flow and helping blood vessels to dilate. They may
also reduce the ‘stickiness’ of the blood and reduce some of the
inflammatory markers which are associated with an increased risk of
heart and blood vessel disease. However, dark chocolate contains much
higher levels of antioxidants than milk chocolate and this is an
important consideration when looking at the research and something the
authors of this recent paper say needs to be considered in future
studies.
So, what does all of this mean when it comes
to enjoying a few chocolate Easter eggs? Despite the possible health
benefits, chocolate doesn’t belong in a class with other healthy foods
such as fruit, vegetables and wholegrains. Chocolate is high in fat and
consequently energy so is best eaten in small amounts, particularly if
you are watching your weight. The key is to choose good quality dark
chocolate, stick to small amounts and take your time to eat and enjoy
it! And to support cocoa farmers and their families, choose Fairtrade chocolate.
Read more:
- Chocolate and risk of chronic disease: a systematic review and dose-response meta-analysis.
- The emerging role of flavonoid-rich cocoa and chocolate in cardiovascular health and disease.
Kate Marsh is an is an Advanced Accredited Practising Dietitian, Credentialled Diabetes Educator and health and medical writer with a particular interest in plant-based eating and the dietary management of diabetes and polycystic ovary syndrome (PCOS).
Contact: Via her website www.drkatemarsh.com.au.
THE INTERNATIONAL STANDARD FOR GI TESTING METHODOLOGY – 10th ANNIVERSARY
It’s been 10 years since the International Standards Organisation first ‘gazetted’ the ISO Standard for glycemic index testing methodology (ISO 26642:2010). The creation of the Standard was a truly global affair, involving committees from Australia, Canada, France, South Africa, and other countries. It was an important milestone in the history of the GI because it helped ensure that laboratories around the globe used the exact same process, and that the values published were truly comparable (comparing like-with-like).
The Standard requires that at least 10 volunteers are tested using a 50 g available carbohydrate portion of the test food (25 g can be selected if there are concerns about the physical size of the portion). What’s critically important is that the standard reference food (usually glucose) is tested a minimum of 2 times and preferably 3 times. This is because a person’s glucose tolerance varies from day-to-day in ways that are difficult to predict. For example, person A might have an ‘area under the curve’ to 50 g glucose of 100 units on one day and 150 units on the next. On average, it might be 125 units and that’s the value that will be used for comparison with the test food.
Reliable GI values can only be generated when standardised in vivo methodology is used. Last year, Dr Tom Wolever and colleagues compared the operation of the ISO standard for GI methodology in 3 different labs (Australia, Canada and France). Six foods were tested by each lab and compared. There were no differences between labs but the standard deviation (a measure of the range of values) was different for each food, ranging from as low as 2 to as high as 7. The findings indicate that the ISO method is sufficiently precise to distinguish foods that have a low GI (55 or less) from those with a high GI (70 or more) with a very high probability (97-99%).
Unfortunately, the relevance of the GI to health continues to be debated. One reason is that some consider that the GI is too variable between people, or that each individual has a unique physiology that means the average ranking of high to low GI foods is not applicable to them. After many years of testing the GI of hundreds of foods on a daily basis in thousands of individuals, we believe there is no such thing as an ‘individual GI’. Day-to-day variability in glucose tolerance is a more likely explanation for unexpected differences in glycemia.
This year will also see the publication of a 2020 version of the international tables of GI. These were first published by our group in the American Journal of Clinical Nutrition in 1995. Although they proved very popular, the tables included values that were actually not entirely reliable, e.g. a GI value for carrots was obtained using only 5 people (and to this day, many people think carrots are a high GI food!). Those tables made it easier to code food composition tables with the GI values of carbohydrate foods and facilitated targeted research. Suddenly, carbohydrate nutrition was not just about sugars vs starches, but high vs low GI. A second set of tables were published in 2002 and a third set in 2008. It is pleasing that they remain amongst the most widely cited articles in nutrition science.
Read more:
- ISO 26642:2010 Food products — Determination of the glycaemic index (GI) and recommendation for food classification
- Glycemic Index and Insulinemic Index of Foods: An Interlaboratory Study Using the ISO 2010 Method
Professor Jennie Brand-Miller holds a Personal Chair in Human Nutrition in the Charles Perkins Centre and the School of Life and Environmental Sciences, at the University of Sydney. She is recognised around the world for her work on carbohydrates and the glycemic index (or GI) of foods, with over 300 scientific publications. Her books about the glycemic index have been bestsellers and made the GI a household word.
