25 July 2014

Tea Time

Serving tea. (multiple websites)
Welcome back. Come in; please sit down. Would you care for a cup of tea? 

I don’t remember when I started drinking tea before exercising in the morning. Prior to that, my only tea sipping was done in Chinese homes or Asian restaurants and traveling overseas. Though coffee is my friend, I can manage tea. The only time I found it challenging was in northwestern China, where I had to strain out the loose tea leaves with my teeth.

Loose-leaf tea served
in thermos at hotel in
Altay, China, 1982.
But this isn’t about me; it’s about tea. Given my earlier post on coffee (Caffeine, Health and Memory), a report on tea was warranted. That earlier post relied in part on information from the Berkeley Wellness Letter, and I’m again indebted to that source for pointing me to The Fifth International Scientific Symposium on Tea and Human Health and summarizing key findings. Before leaping into the latest, I’ll offer a little background, which you’re welcome to skip.

Tea Facts

Worldwide, tea is second only to water as the most popular drink. In 2011, Americans drank over 5 billion gallons, about 85% as iced tea. Black, green, oolong and white teas all come from the same plant species, Camellia sinensis. Their differences result from leaf stage when harvested, processing and exposure to air. (Herbal teas are not true teas.)

Tea chemistry depends on the tea variety, growth factors and processing, as well as on how the processed leaves are stored, brewed and served. Similar to coffee, cocoa and many fruits and vegetables, tea is loaded with polyphenols, particularly flavonoids such as catechins, which have antioxidant and other potentially useful properties and different effects on the body. On average, tea has about 40% of the level of caffeine found in coffee.

Latest Findings about Tea

The jury is still out on whether tea can improve health, but research findings are generally positive. Unlike coffee, it’s hard to find any negatives about tea.

The most promising results involve cardiovascular disease, where observational studies have found reduced risk of disease and stroke. Studies have also shown slightly lower LDL (bad) cholesterol and blood pressure and other improvements, such as inhibiting blood clotting.

Green tea extracts have slowed different cancers in lab studies, though results with humans have been conflicting. Similarly, lab studies have supported tea for improving cognitive function, but studies with humans have been limited. More consistent results have been obtained with tea or tea compounds for improving blood sugar control or reducing risk of type 2 diabetes.

Some studies indicate tea, especially green tea, has a modest weight-loss effect; however, concentrated green tea extracts have not produced weight loss in overweight people. Moreover, catechins contained in supplements may interact with medications and possibly damage the liver.

There’s evidence that tea, particularly black tea, may reduce the risk of Parkinson’s and other neurogenerative diseases. Though more research is needed, there’s also evidence that bone and dental health benefit from tea.

Wrap Up

I started drinking tea, green tea, with milk before exercising because it was too early in the morning to caffeinate with coffee and I’d read about tea’s health benefits. Several years ago, I started noticing research that, on balance, suggested I was negating tea’s cardiovascular health benefits by adding milk.

Although the effects of adding milk weren’t formally addressed in the latest symposium, a sampling of the attending scientists found general agreement that milk would indeed reduce the benefits, the extent depending on how much milk and other factors.

Unique approach to serving
 tea. (multiple websites)
I suppose the real question is whether one drinks tea for pleasure or health or as a substitute for coffee or all of the above. Oh well, if I could learn to strain the tea leaves through my teeth, I can get used to tea without milk. Thanks for visiting.

P.S.

-Berkeley Wellness Letter article on tea: www.berkeleywellness.com/healthy-eating/food/article/tea-benefits-research-wrap?s=EFA_140417_001&st=email&ap=ed
-Information about tea and the 5th International Scientific Symposium from the Tea Assoc. of the USA, Specialty Tea and Tea Council of the USA: www.teausa.com/14634/fifth-international-scientific-symposium

It appears that, every few years, scientists working on tea and human health from around the world have gotten together in Washington, DC, for a one-day plenary session on new and emerging science on the topic. Proceedings are eventually released, generally at least a year later, though I didn’t locate those for the 1st symposium.

 
-Proceedings of 5th International Scientific Symposium on Tea and Human Health, held Sep 2012, were published Dec 2013 as a supplement to The American Journal of Clinical Nutrition: ajcn.nutrition.org/content/98/6.toc
-Proceedings of 4th Symposium in Journal of Nutrition:
jn.nutrition.org/search?tocsectionid=Supplement:+Proceedings+of+the+Fourth+International+Scientific+Symposium+on+Tea+and+Human+Health&sortspec=date&submit=Submit

-Examples of milk and tea interaction research and reviews:
www.npr.org/blogs/thesalt/2012/09/27/161895873/health-benefits-of-tea-milking-it-or-not
www.ncbi.nlm.nih.gov/pubmed/22254119
eurheartj.oxfordjournals.org/content/early/2007/01/09/eurheartj.ehl442.full

2 comments:

Bill Teng said...

An interesting related article on food containing antioxidants:
http://www.motherjones.com/tom-philpott/2014/07/everything-we-know-about-antioxidants-and-vitamins-wrong; another case for exercise.

warren said...

Thank you.