Is white wine as good as red?

Thursday October 16 2008

“White wine is as good for your heart as a drop of the red stuff,” reported The Sun . It said that red wine is known to cut risk of heart attack by lowering cholesterol. This is thanks to resveratrol, a chemical found in grape skin. Although white wine does not contain the skin, tests on rats found it contained other protective chemicals. The Sun added that the researchers said that beer is also cardioprotective.

This study was an animal study, in which 120 rats were used to compare the ability of white wine, red wine and three of their principle components to protect the animals’ hearts against the damage caused by a simulated heart attack. The components examined were resveratrol, tyrosol and hydroxytyrosol, which are all phenolic compounds and present in a variety of foods. They are thought to have beneficial “antioxidant” effects. The finding that all the treatments tested, including a Lambrusco and a Soave, had similar effects to each other may lead to further research. At present, there is not enough evidence to support claims that these drinks, acting through phenolic compounds, have cardioprotective effects.

Where did the story come from?

Jocelyn Dudley and colleagues from the Cardiovascular Research Center at the University of Connecticut School of Medicine, US, and the University of Milan, Italy carried out this research. The study was supported in part by grants from the National Institutes of Health. The study was published in the peer-reviewed scientific journal, Journal of Agricultural and Food Chemistry.

What kind of scientific study was this?

The researchers say it is generally believed that some form of “cardioprotection” is given by drinking red wine. In this animal study, they wanted to test whether other varieties of wine, including white wine and champagne, had similar properties to red wine, and which constituents of wine gave it its cardioprotective properties.

To investigate this, the researchers tested the activity of several enzymes including the activity of citrate synthase, an enzyme that works within the mitochondria (the “power houses” within the cells) in rats that had been fed one of seven test substances.

The rats were fed with either: 1ml straight alcohol (12%); a white wine (a Soave Doc Classico 2004), a red wine (Reunite Lambrusco, Daunia), or the phenols tyrosol, hydroxytyrosol or resveratrol, all in a dose calculated from their weight. Phenols are chemicals found in a variety of foodstuffs that are thought to have anti-oxidant effects. The phenols were dissolved in 12% ethanol.

The rats were killed after 14 days of the free feeding, and their hearts supported artificially so that heart function could be tested and several cellular tests could be carried out.

After death, the rat hearts were perfused in an “isolated working heart model”. In this model, the rats’ hearts were removed and a solution containing oxygen and essential nutrients was pumped through them. The inflow to the heart and the outflow lines were blocked for 30 minutes to simulate a heart attack and then opened again. Heart function was measured during this time. At the end of this period the final cellular tests were performed, including tests of heart attack size, measures of cellular death, swelling of the mitochondria (known as the ‘power house’ parts of a cell), and other protein and enzyme tests.

What were the results of the study?

The researchers say they discovered that “each of the wines and their components increased the enzymatic activities of the mitochondrial complex and citrate synthase.” This means that the wines and the phenols each had an effect on the cellular enzymes that the researchers had set out to monitor. They explain that this enzyme activity is an important one for oxidative phosphorylation and ATP synthesis, both essential parts of the pathways by which cells use energy. This could provide part of the explanation as to how wine is supposed to have an effect on the heart.

In an attempt to understand the actions of the phenols further, the researchers looked for and found that the treatments produced increases in a number of other proteins in heart muscle also thought to protect the heart.

What interpretations did the researchers draw from these results?

The researchers simply say that “the results of this study suggest that white wine can provide cardioprotection similar to red wine if it is rich in tyrosol and hydroxytyrosol.”

What does the NHS Knowledge Service make of this study?

The findings of this study should be kept in perspective. The investigation of phenols found in food and wine is a valid area of scientific research, and future research could potentially prove that some components of wine have a benefit. However, much research needs to be done before it can be proved conclusively that specific components of wine can protect the human heart.

Analysis by Bazian
Edited by NHS Choices