Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Researchers warn milk eliminates cardiovascular health benefits of tea

09.01.2007
Research published on-line today (Tuesday 9 January) in European Heart Journal[1] has found that the protective effect that tea has on the cardiovascular system is totally wiped out by adding milk.

Tests on volunteers showed that black tea significantly improves the ability of the arteries to relax and expand, but adding milk completely blunts the effect. Supporting tests on rat aortas (aortic rings) and endothelial (lining) cells showed that tea relaxed the aortic rings by producing nitric oxide, which promotes dilation of blood vessels. But, again, adding milk blocked the effect.

The findings, by cardiologists and scientists from the Charité Hospital, Universitätsmedizin-Berlin, Campus Mitte, Germany, are bad news for tea-drinking nations like the British, who normally add milk to their beverage. The results have led the researchers to suggest that tea drinkers who customarily add milk should consider omitting it some of the time.

Their study showed that the culprit in milk is a group of proteins called caseins, which they found interacted with the tea to decrease the concentration of catechins in the beverage. Catechins are the flavonoids in tea that mainly contribute to its protection against cardiovascular disease.

Senior researcher Dr Verena Stangl, Professor of Cardiology (Molecular Atherosclerosis) at the hospital, said: “There is a broad body of evidence from experimental and clinical studies indicating that tea exerts antioxidative, anti-inflammatory and vasodilating effects, thereby protecting against cardiovascular diseases. As worldwide tea consumption is second only to that of water, its beneficial effects represent an important public health issue. But, up to now, it’s not been known whether adding milk to tea, as widely practised in the UK and some other countries, influences these protective properties. So, we decided to investigate the effects of tea, with and without milk, on endothelial function, because that is a sensitive indicator of what is happening to blood vessels.”

Sixteen healthy postmenopausal women drank either half a litre of freshly brewed black tea, black tea with 10% skimmed milk, or boiled water (as a control) on three separate occasions under the same conditions. The endothelial function of the brachial artery in the forearm was measured by high resolution ultrasound before and two hours after drinking, with measurements being taken every 15 seconds for up to two minutes a time.

Said first author Dr Mario Lorenz, a molecular biologist: “We found that, whereas drinking tea significantly increased the ability of the artery to relax and expand to accommodate increased blood flow compared with drinking water, the addition of milk completely prevents the biological effect. To extend our findings to a functional model, we determined vasodilation in rat aortic rings by exposing them to tea on its own and tea with individual milk proteins added, and got the same result.”

Milk contains a number of different proteins: by testing each one separately, the researchers found that it was the three caseins that accounted for the inhibiting effect, probably by forming complexes with tea catechins.

Said Dr Stangl: “The well-established benefits of tea have been described in many studies. Our results thus provide a possible explanation for the lack of beneficial effects of tea on the risk of heart disease in the UK, a country where milk is usually added.”

She said their findings could also have implications for cancer, against which tea has also been shown to be protective. “Since milk appears to modify the biological activities of tea ingredients, it is likely that the anti-tumour effects of tea could be affected as well. I think it is essential that we re-examine the association between tea consumption and cancer protection, to see if that is the case.”

Said Dr Lorenz: “It is important to bear in mind that green tea is almost exclusively drunk without milk. So we are talking only about those countries and regions where black tea is consumed and where milk is added. We certainly don’t want to dismiss the consumption of black tea: the results of our study merely attempt to encourage people to consider that, while the addition of milk may improve its taste, it may also lower its health-protective properties.”

Dr Stangl said that another important lesson from their research was that it was vital in nutritional studies to exclude confounding factors as far as possible. Often, the effects of a single nutritional compound or beverage such as red wine, olive oil and so on, are analysed. But, it is difficult to assign clearly the observed effects and separate them from the surrounding food matrix (such as adding milk) that may bias results. It was therefore important to collect all data accurately and include potentially confounding factors in the analysis.

She said that the team was now in the process of comparing the effects of green and black tea on vascular function. “It’s an ongoing question whether green tea, with its higher catechin content, is superior to black tea in regard to endothelial function. In addition, because of the antiatherogenic potential of tea ingredients, we want to investigate the effects of the ingredients on chronic cardiovascular processes such as the development of restenosis (re-narrowing of arteries) after catheter procedures.”

[1]Addition of milk prevents vascular protective effects of tea. European Heart Journal. doi:10.1093/eurheartj/ehl442.

Margaret Willson | alfa
Further information:
http://www.oxfordjournals.org/our_journals/eurheartj/press_releases/freepdf/ehl442.pdf

More articles from Health and Medicine:

nachricht Hot cars can hit deadly temperatures in as little as one hour
24.05.2018 | Arizona State University

nachricht 3D images of cancer cells in the body: Medical physicists from Halle present new method
16.05.2018 | Martin-Luther-Universität Halle-Wittenberg

All articles from Health and Medicine >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Powerful IT security for the car of the future – research alliance develops new approaches

The more electronics steer, accelerate and brake cars, the more important it is to protect them against cyber-attacks. That is why 15 partners from industry and academia will work together over the next three years on new approaches to IT security in self-driving cars. The joint project goes by the name Security For Connected, Autonomous Cars (SecForCARs) and has funding of €7.2 million from the German Federal Ministry of Education and Research. Infineon is leading the project.

Vehicles already offer diverse communication interfaces and more and more automated functions, such as distance and lane-keeping assist systems. At the same...

Im Focus: Molecular switch will facilitate the development of pioneering electro-optical devices

A research team led by physicists at the Technical University of Munich (TUM) has developed molecular nanoswitches that can be toggled between two structurally different states using an applied voltage. They can serve as the basis for a pioneering class of devices that could replace silicon-based components with organic molecules.

The development of new electronic technologies drives the incessant reduction of functional component sizes. In the context of an international collaborative...

Im Focus: LZH showcases laser material processing of tomorrow at the LASYS 2018

At the LASYS 2018, from June 5th to 7th, the Laser Zentrum Hannover e.V. (LZH) will be showcasing processes for the laser material processing of tomorrow in hall 4 at stand 4E75. With blown bomb shells the LZH will present first results of a research project on civil security.

At this year's LASYS, the LZH will exhibit light-based processes such as cutting, welding, ablation and structuring as well as additive manufacturing for...

Im Focus: Self-illuminating pixels for a new display generation

There are videos on the internet that can make one marvel at technology. For example, a smartphone is casually bent around the arm or a thin-film display is rolled in all directions and with almost every diameter. From the user's point of view, this looks fantastic. From a professional point of view, however, the question arises: Is that already possible?

At Display Week 2018, scientists from the Fraunhofer Institute for Applied Polymer Research IAP will be demonstrating today’s technological possibilities and...

Im Focus: Explanation for puzzling quantum oscillations has been found

So-called quantum many-body scars allow quantum systems to stay out of equilibrium much longer, explaining experiment | Study published in Nature Physics

Recently, researchers from Harvard and MIT succeeded in trapping a record 53 atoms and individually controlling their quantum state, realizing what is called a...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

In focus: Climate adapted plants

25.05.2018 | Event News

Save the date: Forum European Neuroscience – 07-11 July 2018 in Berlin, Germany

02.05.2018 | Event News

Invitation to the upcoming "Current Topics in Bioinformatics: Big Data in Genomics and Medicine"

13.04.2018 | Event News

 
Latest News

In focus: Climate adapted plants

25.05.2018 | Event News

Flow probes from the 3D printer

25.05.2018 | Machine Engineering

Less is more? Gene switch for healthy aging found

25.05.2018 | Life Sciences

VideoLinks
Science & Research
Overview of more VideoLinks >>>