January 08, 2007
Benefit Of Tea Cancelled By Milk

The English should stop adding milk to their tea.

Research published on-line (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.

Proteins in milk probably bind to the catechins and render them unavailable.

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."

In East Asian countries where green tea is popular the use of milk in tea is relatively rare. So they are deriving a greater benefit from tea drinking.

High resolution ultrasound allowed measure of the effects of tea and milk on an artery.

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.

Casein proteins make up a substantial portion of cheese. This suggests that red wine (which has a healthy amount of catechins) and cheese is a bad combination. Chocolate milk similarly blunts the effects of the catechins in the chocolate. Drink your wine with nuts. The nuts have their own beneficial compounds such as another type of flavonoids called anthocyanins (tea has some too). As for chocolate milk: Why dilute something as great as chocolate with mere milk?

Casein proteins show up as food additives in a variety of foods and you can watch for the terms caseinate, casein, milk solids, milk protein, and curds as indicators of their presence.

Share |      Randall Parker, 2007 January 08 06:26 PM  Aging Diet Studies


Comments
cancer_man said at January 8, 2007 10:58 PM:

It interesting that a recent study out of Japan showed heart benefits from drinking green tea but no reduction in cancers.

ScottyB said at January 9, 2007 11:03 AM:

So how much can we infer from this study? Does it tell us that dairy in general is bad for you because of its inflammatory properties? Or, does it just tell us that we shouldn't drink tea and milk in the same sitting?

I've read anecdotal reports of how/why we shouldn't be consuming dairy products, but this report seems to offer quantitative data on why dairy is bad.

Personally, I have drunk tons of milk (literally) since childhood. I still do because it is a good, cheap source of protein and calcium. But I would switch to soy milk if there is enough evidence to say the costs outweigh the benefits.

Any thoughts?

jojo said at January 9, 2007 3:14 PM:

What about Whey protein? It has great absorbtion qaulities- but, fundamentally, it's still dairy.

Randy said at January 9, 2007 8:08 PM:

I switched from cows milk to soy milk in California 17 years ago when I married my Chinese wife
and experienced soy's evolution from a bean flavored water to today's richly textured,
slightly sweet, calcium and vitamin enriched beverage sold today.

The switch resulted in a conscious diet made up of foods least likely to insult
the digestive system and improve longevity.

gil said at January 12, 2007 11:39 AM:

Randy,

Soy is far from perfect. It almost certainly has an adverse affect on thyroids. I believe I developed mild hypothyroidism from consuming too much of the product. If continued unchecked I'm very sure I would have developed a goiter by now or worse. There is also evidence that soy laden isoflavones genistein and equol are toxic in large amounts (??) in estrogen sensitive tissues throughout the body (more male than female), and have been tied to activating some auto-immune response (in both).

Anyone who is a vegetarian, and is heavily soy based for more than 5 years, especially if feeling sluggish and or tired and/orloose much weight even w/ exercise, should have their Thyroid levels checked immediately for hypothyroidism (thats hypo not hyper).

I drink rice milk now, which is so far innocuous and just as vitamin enriched.

ddm said at January 29, 2007 12:34 PM:

Seems like soy milk does not have caseins, so would be OK to add to tea, albeit with all the above caveats about not over doing it. Reasonable or not?

Tim Brandt said at September 7, 2008 12:15 PM:

I'm upset im 43 year old Male who smokes and has been drinking tea as far as i can remember, With lot's of milk and sugar soo did i not get any benefits at all from Tea due to the moelucular breakdown of milk added with it?

Ryan W. said at October 10, 2008 12:54 AM:

While I don't believe that oxalates cause kidney stones, oxalate seem unfavorable and milk helps remove it from tea.
http://findarticles.com/p/articles/mi_m0854/is_6_26/ai_n18616060

There are also some assertions that the catechins in tea are removed by the formation of micelles with casein.

http://crobm.iadrjournals.org/cgi/reprint/13/2/184.pdf

The theaflavin-casein association seems to be reversable.
http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6T6R-4H74MCH-8&_user=10&_rdoc=1&_fmt=&_orig=search&_sort=d&view=c&_version=1&_urlVersion=0&_userid=10&md5=91e7821735b4c194bf8c46882f49a399

The methods of the original study asserted that; "Changes in the arterial diameter were measured every 15 s for up to 2 min"
http://eurheartj.oxfordjournals.org/cgi/content/full/ehl442v1#SEC4

Given that casein doesn't seem to irreversably destroy tea theaflavins, isn't it possible that these scientists just didn't test their subjects long
enough to unearth a delayed absorption of the catechins?

gejala stroke said at August 29, 2016 7:41 PM:

Gejala Storoke ringan dan cara menanganinya secara alami harus diperhatikan selalu secara serius , karena saat ini kasus penyakit stroke banyak terjadi dikalangan masyarakat dari mulai stroke ringan hingga stroke berat.
Meski yang dialami masih gejala stroke ringan tapi penanganannya harus secara tepat karena bisa berakibat fatal jika tidak diatasi dengan obat stroke yang ampuh. Sebelum kita membahas lebih lanjut mengenai pengobatan stroke, maka kita harus mempelajari dulu tentang apa itu penyakit stroke, penyebab penyakit stroke, gejala stroke,
serta bahaya apa yang bisa muncul? Setelah itu baru kita bisa memilih obat stroke yang tepat yang akan kita gunakan.

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