Home/Comet assay news/Can cocoa reduce DNA damage?

Can cocoa reduce DNA damage?

Scientists believe that nutrient excess and unbalanced diets can result in overproduction of reactive oxygen species (ROS), which are associated with oxidative stress.  Researchers at the University of Navarra and the Carlos III Health Research Institute have investigated this problem. 

It is known that cocoa extract contains certain antioxidants which inhibit the harmful effects of ROS. It is thought that nutrient excess, particularly from high-fat and high-carbohydrate meals, acts as a stress factor, promoting adipocyte proliferation and causing excessive ROS production.  This can have an impact on the development of obesity-related diseases.  For more information on ROS production and implications, please refer to the original publication.

The human intervention trial described here is apparently the first study to analyse the effect of cocoa extract consumption within ready-to-eat meals and a hypocaloric diet, compared with oxidative stress in overweight/obese middle-aged subjects. The comet assay was used to measure the endogenous level of strand breaks and 8-oxoguanine as well as the antioxidant resistance in lymphocytes from subjects before and after the intervention.

Fifty overweight/obese middle-aged volunteers participated in a 4-week double-blind, randomised, placebo-controlled parallel nutritional intervention. Half of the volunteers received meals supplemented with 1.4g/day cocoa extract, while the other half received control meals, both within a 15% energy restriction diet.

Lymphocytes were isolated and endogenous strand breaks, oxidised bases and resistance to H2O2-induced damage were measured by the comet assay. The medium-throughput comet assay format of 12 minigels per slide (two rows of six minigels on a glass microscope slide) was used. Comets were visualised under a fluorescence microscope and the semi-automated image analysis system Comet Assay IV (Perceptive Instruments) was used to evaluate them. Fifty comets were evaluated per gel, so 100 comets were evaluated per sample. “Percentage of DNA in tail” was used to describe each of the comets and the median was calculated to describe each sample.  For full experimental conditions and procedures, please refer to the original publication.

The scientist reported the following results:

  • The intake of ready-to-eat meals supplemented with cocoa extract did not show relevant changes in the oxidative status of DNA.
  • When volunteers of both groups were analysed together, a marginal decrease in oxidised bases was observed, which attributed to weight loss.
  • Subjects who started the intervention with higher levels of damage showed a greater reduction in oxidised bases after 4 weeks compared to those who had lower baseline levels.

In conclusion, even if 1.4g of cocoa supplementation for 4 weeks did not show notable changes in terms of antioxidant status of DNA, the energy restriction showed a slight decrease in oxidised bases.  This was observed by the researchers to a greater extent in subjects who started the intervention with higher levels of damage.

However, the researchers believe that the inverse associations found between oxidised bases and some cocoa-derived metabolites suggest that a protective effect might be seen in a longer period of time, or in subjects with higher baseline DNA damage.  The authors suggest that further studies are justified to assess the antioxidant effect of cocoa extract on oxidative damage to DNA.

This case study is based upon:

Assessment of DNA damage using comet assay in middle-aged overweight/obese subjects after following a hypocaloric diet supplemented with cocoa extract
Idoia Ibero-Baraibar, Amaya Azqueta, Adela Lopez de Cerain, J. Alfredo Martinez and M. Angeles Zulet.
Mutagenesis (2015) 30 (1): 139-146.

About Us

This site is maintained by Perceptive Instruments, industry-leading experts in image analysis for the comet assay.

We regularly attend comet assay workshops and contribute to the debate towards regulatory acceptance of the assay.

About Comet Assay IV

Comet Assay IV is the world's fastest, most consistent comet assay scoring system.

For our full range of products, head over to www.perceptive.co.uk