Healthy Andy

A study published in the Journal of the American Medical Association suggests that drinking green tea can help you live longer.  Many studies in the past have examined the specific health benefits of either green tea, or the active antioxidants in green tea, but this study examined the actual consumption of tea and compared it to mortality rates in Japanese adults.

The Ohsaki National Health Insurance Cohort Study

This study began back in the ’90s in Japan, following over forty thousand adults over the age of 40 without any history of major chronic disease (heart disease, cancer, that sort of nasty stuff).  Individuals were followed up on over the course of the next eleven years to see how many had died from any cause. Participants filled out a questionnaire that asked some basic questions about daily nutrition habits, including the consumption of green tea.  This makes this study very similiar to the Nurse’s Health Study, a study that has followed over 100,000 nurses over the course of decades (except, since it’s an American study, they don’t specifically ask about green tea).

For the Ohsaki study, participants were asked if they drank green tea never, occasionally, 1-2 cups per day, 3-4 cups per day, and 5 or more cups per day.  The authors noted that the typical “cup” of green tea is about 100 milliliters (about 3.5 ounces).

By the way, one of the nice things about this study is, the researchers took the time to see if their questionnarie was at all accurate.  They picked a sample of people and had them do a more comprehensive food diary for three days on four seperate occasions.  They found that there was a moderate to strong correlation between reported intake and actual intake.

The Results: Green Tea Makes You Live Longer

After accounting for potentially confounding variables like age or physical activity, the researchers found that the more green tea people drank, the less likely they were to die from any cause.  The effect was obviously most noticeable in the 5 or more cups of tea per day group; if you used non-tea drinkers as a baseline, the hazard ratio was 0.88 for the 5 cups a day drinkers.  This means that for every 1 non-tea drinker, 0.88 tea drinkers died… which basically means green tea makes you live longer.

The effect was even MORE pronounced among women; the hazard ratio was 0.77 for the heavy tea-drinkers.  So for every 100 non-tea drinkers who died, only 77 tea drinkers died of any cause.  The researchers followed these effects for eleven years.

Then, they took a look at more specific causes of death (they reviewed data for seven years for this). They found that green tea consumption significantly reduced the risk of death from cardiovascular disease, but didn’t reduce the risk of death by cancer.  After looking even closer into the data, they found that when it came to cardiovascular disease, the greatest protection was from stroke.  Once again, the effect was most pronounced in women, who had a 42% less chance of death by stroke if they were drinking 5 or more cups per day of green tea (compared to one or less).

This shouldn’t be a big shock to readers of this website- we’ve talked before about how antioxidants make arteries more elastic and pliable (and therefore healthier).  Since strokes are caused by either blockage or rupture of an artery in the brain, healthier arteries are going to be less prone to those kinds of problems.  And I don’t know about you, but I have no deep and burning desire to experience a stroke, so I’m going to keep drinking green tea and live longer than I would have otherwise!

Stay healthy!

By the way, the full text of this study is available online for free at this link:  http://jama.ama-assn.org/content/296/10/1255.long

Is green tea a weight loss supplement?  A surprising number of studies suggest that there is evidence to belive this to be the case.

First off, a couple of side notes.  Green tea has a huge number of health benefits far beyond mere weight loss, from antioxidant and anti-cancer properties to helping you keep your teeth.  I’ve discussed a few of them on this site in the past.  So I consider it a good addition to your health routine irregardless of any weight loss effects.  However, I also feel the need to point out that no weight loss supplement ever invented will beat good old fashioned diet and exercise habits for turning your bulging belly into a flat one.

At best…. at BEST… you can hope for a supplement to enhance your diet and exercise changes by MAYBE 10%.  If you’re trying to get more than that out of a supplement, you’re probably doing a mildly glorified version of smoking crystal meth. 

In case you’re wondering, I do not advise smoking crystal meth for weight loss, or any other reason, really.

Okay, back to green tea and weight loss. A recent meta-analysis out of the University of Connecticut suggests that green tea catechins (these are the antioxidants in green tea) can indeed help with weight loss, but only if there’s caffeine involved.

First off, for those of you unfamiliar with the term “meta-analysis“, that just refers to taking a whole bunch of studies and sort of summing up their results into one bigger group study.  The researchers don’t actually perform a scientific study of their own; they just borrow other people’s data.

They’re nice because you get to pool data into a much larger pile than one study alone can hope to do.  And, they’re cheap and relatively easy, because hey, somebody else did all the hard work of finding subjects and measuring them and poking them with a pointy stick (okay, not that last one). 

The bad news is, they are really, really vulnerable to researcher bias, in that if I’m a researcher and I really, really feel strongly that green tea is a super-fantastic weight loss supplement, I might (consciously or subsconsciously) only select those studies which will support my opinion.  This happens a lot more than you might think, so be aware of this particular limitation.

The Green Tea Weight Loss Meta-Study

In this case, the researchers found 15 studies that compared the use of green tea catechins with caffeiene to the use of the same green tea stuff without caffeine.  Added together, this provided a total of over 1,200 subjects, and when it comes to scientific analysis, more subjects is more better-er, as my Pappy used to say (not really). 

What they found, was that you pretty much had to have green tea plus caffeine in order to see any effect.  Green tea catechins alone didn’t seem to do much, and while caffeiene had some effect, it worked far better if you had green tea added in.  The effects were measurable for body weight, BMI (body mass index), and waist circumference.

Here’s the bad news.  When you read the fine print, this study doesn’t seem quite as strong.  Not every study measured the same things.  The dosages varied (of green tea as well as caffeine), as did the length of time the subjects were followed.  Basically, this was a real patchwork quilt of studies that didn’t seem to fit well together into a meta-analysis.

Still, it gives a crude indication that there’s probably something going on in the whole green tea- weight loss arena.  So let’s look at some more evidence.

The Green Tea Air Chamber Study

One study measured acutal energy expenditure in ten subjects with either placebo, caffeiene, or green tea extract (with caffeine).  Each subject was tested on three seperate occasions under three different conditions.  The researchers found a 4% increase in energy expenditure in the green tea group.  

How did they measure energy expenditure, you ask?  By sealing the subjects in a “respiratory chamber” for 24 hrs and measuring the changes in oxygen and cardon dioxide levels, and then using a fancy-schmancy equation to indirectly guess at how much energy the subjects were burning off.  Frankly, I’m not very familiar with that technique, so I can’t tell you how accurate it is or isn’t.

If we take it as a given that this technique is accurate for estimating energy expenditure, this is a nifty study, but ten subjects is a really small sample size.  This alone put this research more in the “pilot study” category, which is kind of a mini-study that checks to see if we should bother to make a bigger, more expensive study on the subject.  But by itself, it’s not too convincing.

The Bigger, More Expensive Green Tea Weight Loss Study

Okay, here’s a really good one.  A study published in the Journal of Nutrition in 2009 took a bunch of people, had them keep their caloric intake consistent, and had them exercise for three hours a week (some of it supervised).  Half of them got a caffeiene only supplement, the other had a green tea extract/caffeiene mix (the caffeiene level was the same as the other group).  Twelve weeks later, they checked the results.

What they basically found was that the green tea extract enhanced the exercise-induced weight loss.  Not a lot, but since they had over a hundred subjects, it was enough to be noticed.  What was most interesting was the effect on abdominal fat distribution.

You see, they didn’t just weigh these people.  They used CT scans to find out exactly how fat their bellies were before and after.  While the effects of green tea on body weight were only mildly noticeable, there was a much more obvious effect in abdominal fat distribution.  Specifically, the caffeiene only group had an average total abdominal fat area decrease of 0.3%, while the green tea group had a total abdominal fat loss of 7.7% on average.

I like this study because it directly measures what we really care about (does green tea make my big belly get smaller) rather than indirectly measuring something that maybe, kinda-sorta, somehow has something to do with what we want (like the energy expenditure air chamber thing).  Plus, they had a good sample size and simple-but-solid study design… the kind that’s harder to screw up.

And, they confirm what I told you up at the top of the page.  Supplements don’t do THAT much.  It’s the diet and exercise that will pull the heavy weight.  Even with large levels of green tea supplements (over 600 mg/day), there was only a small difference in fat loss over control… and these people were exercising, as well. 

So, in the great green tea weight loss supplement debate, remember that supplements only nudge you in the right direction… diet and exercise are going to do the real work in fat loss.

Article citations:

Meta-Study:

Effect of green tea catechins with or without caffeine on anthropometric measures: a systematic review and meta-analysis.Phung OJ, Baker WL, Matthews LJ, Lanosa M, Thorne A, Coleman CI.Am J Clin Nutr. 2010 Jan;91(1):73-81. Epub 2009 Nov 11. Review.

Itty-Bitty Respiratory Chamber Study:

Dulloo AG, Duret C, Rohrer D, et al Efficacy of green tea extract rich in catechin polyphenols and caffeine in increasing 24-h energy expenditure and fat oxidation in humans. Am J Clin Nutr 1999;70:1040–5

Green tea catechin consumption enhances exercise-induced abdominal fat loss in overweight and obese adults.Maki KC, Reeves MS, Farmer M, Yasunaga K, Matsuo N, Katsuragi Y, Komikado M, Tokimitsu I, Wilder D, Jones F, Blumberg JB, Cartwright Y.J Nutr. 2009 Feb;139(2):264-70. Epub 2008 Dec 11.

 More and more news on the health benefits of green tea keep pouring in.  The latest comes from Japanese researchers published in the journal Chinese Medicine.

They did what’s called a literature review, which is what it sounds like.  Rather than set up a specific experiment and generate new data, the researchers instead sift through many, many other research papers and try to use the sum of that data to achieve some new insights.

These are tricky to do, more tricky than you might think.  The main thing is, what studies do you include in your review?  If you go cherry-picking this article you like here, that article you like there, you may end up biasing your results significantly. 

At the same time, there’s a lot of junk science out there, my friends.  You can’t take every article, because some are just crap (here’s an example of a bad study on fish oils) and will skew your results in an inaccurate direction.  So it can be a bit of a delicate dance.

Health Benefits Of Green Tea

So what did the researchers find?  Well, after selecting 105 articles to go through, the researchers reported:

• There are very potent antioxidants in green tea called catechins that strongly contribute to the overall antioxidant network in the body.  Catechins keep coming up over and over again in the study, and if you read much at all about green tea, you’re going to keep coming across the word “catechins”. This antioxidant effect is actually measurable in the blood plasma (by reducing signs of oxidative stress).  For more on how antioxidants actually work, find out how blueberries will take a bullet for you.
• Going back to catechins, there’s some evidence that they help prevent degenerative diseases of various kinds, including cardiovascular diseases like hypertension and coronary heart disease (clogged arteries).  For more on this, read this article on antioxidants and arteries.  Trigycleride levels are also reduced when green tea extracts are used.
• Green tea and extracts of green tea like EGCG can help with obesity.  It’s possible that this is due to an increase in thermogenesis (creation of body heat), or it could be due to more optimized use of glucose.
• Which leads us to the health benefits of green tea for diabetics.  Green tea and it’s extracts seem to help in glucose metabolism… there is a measurable reduction of glucose levels in the presence of green tea anitoxidants.
• Various anti-fungal and anti-viral (including influenza) benefits were found, including Candida Albicans specifically .
• How about bone density?  There’s evidence green tea can help with increased bone mineralization (density), which makes sense considering this study on how green tea helps your teeth (actually, it helps reinforce that study quite a bit).

In short, green tea is pretty amazing stuff.  A lot of the benefits can be attributed to the strong antioxidant properties found in green tea, but there seems to be a lot more to it than that.  As much as we know, there’s still a long way to go to understand exactly how this stuff is so darn good for us.

By the way, green tea is actually rather low in caffiene.  Ounce for ounce, it has about one-fifth the caffiene content of a cup of coffee.  Which is good for me, because too much caffiene makes my heart explode out of my chest.

Fire down some green tea and stay healthy!

I guess dentistry is on my mind today, because this is my second post today about teeth.  An article from Preventitive Medicine suggests drinking green tea helps to protect your teeth.

The study checked a group of people in Japan and basically found that those folks who drank green tea had more of their teeth.  Those people who didn’t drink green tea?  You guessed it.  Less teeth.

While it’s possible that simply the act of drinking tea is what helps- sort of like a mouthwash- the same protective effect didn’t hold true for coffee.  So it’s more likely that some of the anti-microbial effects of green tea (from beneficial chemcials called catechins) are the cause.

Those catechins have been shown to kill off the bacteria that causes gum and tooth decay, and while they’re in green tea, they aren’t in coffee. Actually, catechins do more than just protect your teeth.  They’re wonderful antioxidants that promote all kinds of health benefits… this whole tooth protection thing is just icing on the cake.

By the way, speaking of icing, the green tea has to be unsweetened.  Adding sugar kills the protective effect.  Still, one more reason to drink green tea!

Stay healthy!

Source article: http://news.discovery.com/human/green-tea-teeth-dental.html