Wednesday, October 26, 2016

Sleep and odor memory

Was searching for something quite different when I came across a paper discussing how sleep helps with odor memory.*

In one part of this study, the participants (who were all male, btw) learned to recognize six different odors (though not name them). Then they slept, and the next day were asked to identify which odors they had or had not experienced the night before from among a set of twelve odors. 

By administering certain drugs or placebo just before sleep, the researchers were able to determine that the participants consolidated their memory for the odors during slow-wave deep sleep. 

The graph below shows the results of one part of the study. In the wake condition (on the left), participants were kept awake through the night. While their recognition ability under this condition was good, it was not as good as their ability after a period (3 hours) of slow-wave sleep, followed by staying awake (compare Placebo/Wake to Placebo/Sleep). The drug clonidine obliterated the effect of slow-wave sleep on recognition. 

Was fascinated to observe that the odors they used included several that are typical in tea, such as linalool oxides, damascenone, and 2-hexenal.** 

Conclusion: if you want to learn to recognize (and eventually name, of course) different odors in tea, it helps to get a good night’s sleep!

* Gais S, Rasch B, Dahmen J, Sara S, Born J. The Memory Function of Noradrenergic Activity in Non-REM Sleep. Journal Of Cognitive Neuroscience [serial online]. September 2011;23(9):2582-2592. Available from: Academic Search Premier, Ipswich, MA. Accessed October 26, 2016.

** Incidentally, the authors qualified these odors as being “unfamiliar”— but they probably are familiar to those of you who have been studying tea aromas.

Wednesday, October 12, 2016

Tea and cardiovascular disease

The edition before the last of World Tea News talks about an article in the American Journal of Medicine that suggests that consumption of tea may help prevent both calcium deposition in coronary arteries and cardiovascular events.*

Interesting news, so I thought I should take a look at the original article, which was published on line September 15, 2016.** In this post, I will talk about the baseline data, with follow-up data discussed in future posts.

The article is based on data from the Multi-Ethnic Study of Atherosclerosis (MESA). This study was prospective, which means that it followed a sample of 6814 men and women aged 44 to 84, at 6 different U.S. medical centers. It  began in 2000, finished recruiting participants in 2002, and ended on December 31st, 2013. For the present analysis, data from 6508 people were used.

Participants provided dietary information when they entered the study and every 9 to 12 months thereafter. Computed tomography scans of the degree of coronary artery calcification were done at the beginning of the study and at 4 times thereafter. Not everyone participated at each scan, and it is not clear from the write-up whether everyone was actually scanned twice. That said, the analysis took into account the time between the first and the second scan in order to obtain information about changes over time. 

Another feature of the study was the attempt to take into account a multitude of factors that are known to contribute to cardiovascular disease (CVD), for example smoking, in order to tease out the contributions of tea, coffee, and total caffeine consumption to CVD.*** On the other hand no effort was made to distinguish among types of tea consumed or between caffeinated and decaf coffee.

So what do the baseline results tell us? 

First, it is striking, though not too surprising, that the people who had calcification in their arteries at baseline were older and more likely to be white and male than people who had none, and for the most part they were experiencing the known predictors of cardiovascular disease, such as hypertension, diabetes, and family history of coronary heart disease, “good” and “bad” cholesterol levels, and exercise time per week. Notable exceptions: there was no association with body mass index, though the mean was on the high side at 28.2±5.4; the people with no calcification actually ate slightly more fat, and other dietary measures, such as vegetable and fruit consumption, had a minor effect if any—hard to tell from the data given.

CT scan of the chest in cross section (the person's back is below the bottom of the picture), showing calcification in a coronary artery, from This link leads to another  from the Mayo Clinic that discusses how calcification is scored and what it means.

Now for the relationship with tea:

First, 58% of the participants did not drink tea at all, and another 29% drank less than a cup a day—only 13% drank tea on a daily basis…why this huge difference is not explained, of course, but the authors suggest that there may be other unmeasured differences, possibly lifestyle differences, that contribute to both the choice to drink tea and any results concerning arterial calcification and CVD. 

Next, to the calcification results: of the 800 people who drank tea daily at the time of enrollment into the study, about half had no measurable calcification in their arteries and half had some. For further analysis, the authors used a cut-off score which divided people into those who had relatively little to no calcification and those who had significant calcification.
While 13% of the participants drank tea each day, they accounted for slightly more of the participants (at 14%) who did not have significant calcification in their arteries according to their cut-off, and slightly fewer (at 11%) of those with significant calcification at baseline. The big finding is that when the authors took into account (= controlled for) all the cardiovascular risk factors, including age, drinkers of a daily tea had a lower risk of having the larger amount coronary artery calcification. 

Finally, people who drank tea daily at enrollment had fewer cardiovascular events during follow-up—12.3 events per thousand person-years for those who didn’t drink tea at all versus 7.7 events for those who drank tea every day. The difference is slight, but perhaps meaningful, but clearly drinking tea does not . Note that for this analysis, people of Chinese descent were excluded, because they consumed large amounts of tea…and also had fewer cardiovascular events! Which makes one wonder…was their advantage dietary or genetic or both?

When you think about these results, remember how few people drank tea on a daily basis in this study, and remember that those who drink tea may be doing a lot of other things differently or may be different genetically as well. 

So drink your tea for enjoyment—and just maybe you’ll get some cardiovascular benefits as well.

** Miller PE, Zhao D, Frazier-Wood AC, Michos ED, Averill M, Sandfort V, Burke GL, Polak JF, Lima JAC, Post WS, Blumenthal RS, Guallar E, Martin SS, Associations between Coffee, Tea, and Caffeine Intake with Coronary Artery Calcification and Cardiovascular Events, The American Journal of Medicine (2016), doi: 10.1016/j.amjmed.2016.08.038. 

*** Here’s the complete list: age, sex, race/ethnicity, education, smoking (never, former, current), physical activity, total fat, alcohol consumption, fruits quartiles, vegetables quartiles, red meat quartiles, systolic and diastolic blood pressures, use of antihypertensive medications, lipid-lowering medication, anti-diabetic medication, BMI, family history of CHD, diabetes, HDL-cholesterol, total cholesterol, and triglycerides, C-reactive protein and fibrinogen.

Monday, October 3, 2016

Pudina chai and mint as digestif

The Daily Tea has a fine article on chai, with links to different approaches—chai with black tea, of course, but also green tea chai, with origins in Kashmir, and white tea chai.* The author, Carrie Keplinger, also described variations of black tea chai, including pudina chai. 

Pudina** chai “is black tea steeped with mint leaves in milk and water, sweetened to taste… Pudina chai makes a wonderful after-dinner digestif or a soothing remedy for an upset stomach.” Which is one great way to have an after-dinner mint!

Mentha arvensis, from Wikipedia

But why do we have an after-dinner mint as a “digestif?”

I believe the answer lies in mint’s ability to activate TRPA1, the cold receptor. You can find this receptor not just in the mouth and nose, where we sense the cold, but also all the way through the gut. In the gut TRPA1 is attached both to the gut lining cells and to specialized cells, enteroendocrine cells, that regulate gut motility.

When TRPA1 receptors attached to gut lining cells are activated, blood flow to the gut increases.*** When TRPA1 receptors on the enteroendocrine cells are activated, these cells release the hormone serotonin, which in turn causes the gut to start moving what you have eaten down the tract.****

Consequence? your digestion proceeds more quickly and smoothly, and you feel less over-filled! 


** Despite the best efforts of my spell-check system, this word is not “pudding.” Pudina is the Hindi/Urdu name for a wild mint, Mentha arvensis, also know as corn mint and field mint.

*** Toru Kono, Atsushi Kaneko, Yuji Omiya, Katsuya Ohbuchi, Nagisa Ohno, Mas.ahiro Yamamoto. Epithelial transient receptor potential ankyrin 1 (TRPA1)-dependent adrenomedullin upregulates blood flow in rat small intestine. American Journal of Physiology - Gastrointestinal and Liver Physiology Feb 2013, 304 (4) G428-G436; DOI: 10.1152/ajpgi.00356.2012.

**** Nozawa K, Kawabata-Shoda E, Doihara H, et al. TRPA1 regulates gastrointestinal motility through serotonin release from enterochromaffin cells. Proceedings of the National Academy of Sciences of the United States of America. 2009;106(9):3408-3413. doi:10.1073/pnas.0805323106.