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Theaflavins and Heart Health

January 25, 2010 Written by JP    [Font too small?]

As a big fan of movies, quotations from films are often in the forefront of my mind. One line of dialogue that’s made an indelible impression on me is from the 2005 box-office bomb, The Weather Man. In the film, the esteemed actor Michael Caine offers some prescient words of wisdom to his adult son, played by Nicolas Cage. “Do you know that the harder thing to do and the right thing to do are usually the same thing? Nothing that has meaning is easy. ‘Easy’ doesn’t enter into grown-up life”. That advice was given with regard to a failing marriage, but it I think it applies to almost every aspect of life and, quite specifically, to natural medicine.

One of my goals is to try to change a prevalent perception that I see in virtually all sectors of the alternative and conventional medical system. It’s a counterproductive point of view that natural medicine: a) cannot be adequately or fairly studied by using the scientific method; b) natural remedies are more basic or primitive than allophatic medications and treatments and; c) we should expect “black and white” answers to issues regarding the efficacy of holistic therapies. To be clear, this problem is not isolated to the mainstream medical establishment. It extends into the territory of natural health manufacturers, practitioners and even patients.

Here’s the problem in a nutshell: The conventional medical community tends to ignore most natural remedies. But on occasion they do conduct a study or two to scientifically assess the value of a specific practice or supplement. If the results are positive, they’re typically viewed as being “preliminary”. However, if the results are negative or not statistically significant, the remedy in question is considered useless. The problem is that both of these attitudes are over simplifications of the truth. As the old saying goes, “The devil is in the details”. There is no place where that is more true than in the field of medical research.

In order to illustrate how complex it is to properly research an alternative “medicine”, I’d like to present the case of “Theaflavins vs. Cholesterol and Heart Disease”. The reason I’ve chosen this topic is because theaflavins, a class of phytochemicals found primarily in black tea, are currently being marketed as a cardioprotective supplement.

A new study published in the European Journal of Nutrition casts some doubt on the ability of theaflavins to positively augment lipid levels. This surprising finding is based on a new trial conducted on a group of 102 patients with high cholesterol. The men and women in the study were divided into three sections: 1) received a supplement containing 77.5 mg of “purified black tea theaflavins” daily; 2) a mixture of 75 mg theaflavins + 150 tea catechins and 195 mg of tea polyphenols; and 3) a placebo containing a small amount of plant fiber (cellulose).

  • LDL (“bad”) cholesterol, total cholesterol and triglycerides were tested at the start of the study and after weeks 4,8 and 11.
  • There was no significant differences found in the groups receiving any of the three treatments.

The authors of the trial summarized these results in an uncommonly fair minded manner: “Based on these findings it cannot be concluded that tea flavonoids such as theaflavins and catechins are responsible for the putative cholesterol-lowering effect of black tea, at least not with the daily dose applied in the present study”. (1)

This particular trial hasn’t really made much of a splash in the alternative or mainstream media and it’s unlikely to do so anytime soon. But I think it’s important to address it because I believe almost everyone genuinely wants to know which alt-med remedies work and which are a waste of money. That’s why a little detective work is needed here. Theaflavins have been viewed as promising nutraceuticals for managing heart health based on a handful of positive clinical studies that have been trickling in over past several years.

  • The December 2009 edition of the British Journal of Nutrition reports that a black tea extract, rich in theaflavins and thearubigins, effectively lowered blood sugar levels, lipids and improved liver function in a group of lab rats. A modulatory effect on body weight was also noted. (2)
  • Two recent test tube studies provide a plausible rationale for how theaflavins might encourage reductions in cholesterol concentrations. A laboratory experiment from the University of Kentucky discovered that black tea can inhibit “HMG-CoA reductase”, which is the primary mechanism employed by most cholesterol lowering medications. Researchers in the Netherlands offer up another pathway by which theaflavins can alter lipid levels – by decreasing cholesterol absorption through the intestinal wall. This too is a method by which some medications lower lipids. However, it’s important to note that black tea extract has not demonstrated the same safety concerns as its prescription counterparts. (3,4,5)
  • An older study, published in October 2003, determined that drinking 5 cups of black tea/day reduced LDL (“bad”) cholesterol by 11.1%, apolipoprotein B by 5% and lipoprotein(a) by 16.4%. These changes are typically considered favorable with regard to cardiovascular risk. (6)

The cholesterol-lowering track record of black tea first came into question after the publication of the August 2009 issue of the Journal of Alternative and Complementary Medicine. An Iranian study examined the respective effects of two different types of tea on the lipid profiles of 60 diabetic patients over a one month period. The daily consumption of 2 cups of black tea didn’t yield significant changes in LDL, total cholesterol or triglyceride levels. There was, however, a statistically relevant boost in HDL (“good”) cholesterol. (7)

Unlike black tea, green tea supplements are rarely marketed for their ability to influence lipid levels. But a cursory review of the medical literature appears to provide stronger evidence in favor of green tea.

The most recent human trial on green tea involved 33 patients of varying ages (21-71) who were asked to eat a low-fat diet and take either a 250 mg capsule of green tea extract or a placebo for 8 weeks. Half of the participants were given green tea and the remainder the placebo. Blood tests were taken at the start of the trial and at the 8 week mark. After the initial 8 week period, the researchers switched the respective medications given to volunteers. This “crossover” design helps to identify specific changes brought about by the test substance (green tea) vs. the placebo. Minor reductions in LDL (4.5%) and total cholesterol (3.9%) were demonstrated only after the green tea treatment. (8)

A February 2009 trial discovered that a twice-daily dosage of green tea extract, prompted several positive cardiovascular shifts in a group of 111 “healthy adult volunteers”: a drop in both diastolic and systolic blood pressure, LDL cholesterol, malondialdehyde (a measure of oxidative stress) and amyloid-alpha (an inflammatory marker). In addition, a Spanish study from April 2008 found that 5 weeks of daily green tea consumption led to improved vasodilation (vascular function) and a reduction in oxidized cholesterol, which can contribute to plaque accumulation in the arteries and increase risk of heart attacks and stroke. (9,10)

Green Tea + Theaflavins May Improve Cardiovascular Risk Factors
Source: Arch Intern Med. 2003;163:1448-1453. (link)

The comparison of black tea and green tea may be more complex than it seems. A group of researchers from Vanderbilt University Medical Center discovered that combining green tea and (black tea) theaflavins may be just the ticket. A 12 week “double-blind, randomized, placebo-controlled” examination of 240 men and women tested the effects of a once-daily capsule of “theaflavin-enriched green tea extract” (375 mg) vs. a placebo. The results of the trial were quite impressive: an 11.3% decline in total cholesterol, -16.4% LDL choleterol and a 2.3% increase in HDL cholesterol. Unfortunately, the green tea + theaflavin therapy in combination with a low-fat diet did not lower triglycerides. On the upside, there were no significant side effects reported. (11)

The above mentioned studies are a very basic introduction into the world of tea and cardiovascular disease. The next stop on our tea trail will focus on pu-erh tea. If you’ve never heard of or tried this health promoting brew, please make sure to read tomorrow’s column.

Note: Please check out the “Comments & Updates” section of this blog – at the bottom of the page. You can find the latest research about this topic there!

Be well!


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Posted in Food and Drink, Heart Health, Nutrition

10 Comments & Updates to “Theaflavins and Heart Health”

  1. anne h Says:

    great research – as usual JP!

  2. JP Says:

    Many thanks, Anne! 🙂

    Be well!


  3. Nina K. Says:

    Morning JP 🙂

    yepeee a tea-week :-)! i hope there also will be done some studies which are evaluate the health potential of yellow tea and oolong tea. I think the fine graduate differences in fermentation will make some health differences. We will see.

    I need currently very much tea – we have -10°C outside and it seems that it is still going colder – brrrr! *slurping my tamaryokucha (or guricha) green tea*

    Stay healthy!

    Nina K.

  4. JP Says:

    Good day, Nina! 🙂

    Wow! That’s wicked cold! At least I’m happy to know that you’ll be drinking more tea! 😉

    This week I’ll focus on pu-erh tea. But I will indeed touch upon oolong and other teas in upcoming columns. Please stay tuned!

    Be well!


  5. EGCG Says:

    Natural remedies are no studied because medical companies can’t make money with them. As simple as that.

  6. JP Says:

    That’s only part of the problem, in my opinion. There are quite a few studies on natural products being conducted these days. Some of them are even being sponsored by supplement manufacturers and others by independent researchers.

    Be well!


  7. JP Says:

    Updated 05/16/16:


    Nutrition & Metabolism 2016 13:34

    Impact of flavonoid-rich black tea and beetroot juice on postprandial peripheral vascular resistance and glucose homeostasis in obese, insulin-resistant men: a randomized controlled trial

    Background: Insulin-stimulated muscle blood flow facilitates plasma glucose disposal after a meal, a mechanism that is impaired in obese, insulin-resistant volunteers. Nitrate- or flavonoid-rich products, through their proposed effects on nitric oxide, may improve postprandial blood flow and, subsequently, glucose disposal. To investigate whether a single dose of nitrate-rich beetroot juice or flavonoid-rich black tea lowers postprandial muscle vascular resistance in obese volunteers and alters postprandial glucose or insulin concentrations.

    Method: In a randomised, controlled, cross-over study, 16 obese, insulin-resistant males consumed 75 g glucose, which was combined with 100 ml black tea, beetroot juice or control (water). Peripheral vascular resistance (VR), calculated as mean arterial pressure divided by blood flow, was assessed in the arm and leg conduit arteries, resistance arteries and muscle microcirculation across 3 h (every 30-min) after the oral glucose load.

    Results: During control, we found no postprandial response in VR in conduit, resistance and microvessels (all P > 0.05). Black tea decreased VR compared to control in conduit, resistance and microvessels (all P < 0.05). Beetroot juice decreased postprandial VR in resistance vessels, but not in conduit artery and microvessels. Although postprandial glucose response was similar after all interventions, postprandial insulin response was attenuated by ~29 % after tea (P < 0.0005), but not beetroot juice.

    Conclusions: A single dose of black tea decreased peripheral VR across upper and lower limbs after a glucose load which was accompanied by a lower insulin response. Future studies in insulin-resistant subjects are warranted to confirm the observed effects and to explore whether long-term regular tea consumption affects glucose homeostasis.

    Be well!


  8. JP Says:

    Updated 11/18/16:


    Nutrients. 2016 Nov 16;8(11).

    Black Tea Increases Circulating Endothelial Progenitor Cells and Improves Flow Mediated Dilatation Counteracting Deleterious Effects from a Fat Load in Hypertensive Patients: A Randomized Controlled Study.

    (1) Background: Endothelial dysfunction predicts cardiovascular events. Circulating angiogenic cells (CACs) maintain and repair the endothelium regulating its function. Tea flavonoids reduce cardiovascular risk. We investigated the effects of black tea on the number of CACs and on flow-mediated dilation (FMD) before and after an oral fat in hypertensives; (2) Methods: In a randomized, double-blind, controlled, cross-over study, 19 patients were assigned to black tea (150 mg polyphenols) or a placebo twice a day for eight days. Measurements were obtained in a fasted state and after consuming whipping cream, and FMD was measured at baseline and after consumption of the products; (3) Results: Compared with the placebo, black tea ingestion increased functionally active CACs (36 ± 22 vs. 56 ± 21 cells per high-power field; p = 0.006) and FMD (5.0% ± 0.3% vs. 6.6% ± 0.3%, p < 0.0001). Tea further increased FMD 1, 2, 3, and 4 h after consumption, with maximal response 2 h after intake (p < 0.0001). Fat challenge decreased FMD, while tea consumption counteracted FMD impairment (p < 0.0001); (4) Conclusions: We demonstrated the vascular protective properties of black tea by increasing the number of CACs and preventing endothelial dysfunction induced by acute oral fat load in hypertensive patients. Considering that tea is the most consumed beverage after water, our findings are of clinical relevance and interest. Be well! JP

  9. JP Says:

    Updated 01/07/17:


    Asia Pac J Clin Nutr. 2017 Jan;26(1):59-64.

    Black tea consumption improves postprandial glycemic control in normal and pre-diabetic subjects: a randomized, double-blind, placebo-controlled crossover study.

    BACKGROUND AND OBJECTIVES: Postprandial glycemic control is important for prevention of diabetes. Black tea consumption may improve postprandial glycemic control. The major bioactive compounds are polyphenols, black tea polymerized polyphenol (BTPP).This study examined the effect of black tea consumption on postprandial blood glucose and insulin response following sucrose loading in normal and pre-diabetes subjects.

    METHODS AND STUDY DESIGN: This study was a randomized, double-blind, placebo-controlled crossover study. Twenty-four subjects, male and female aged 20-60 years, normal and pre-diabetic, randomly ingested a sucrose solution with a low dose (110 mg BTPP), a high dose (220 mg BTPP) of black tea drink or a placebo drink (0 mg BTPP). Blood samples were collected at 0, 30, 60, 90, and 120 min from commencement of drink ingestion to measure blood glucose and insulin levels.

    RESULTS: The drink containing low dose and high dose BTPP significantly decreased incremental blood glucose area under the curve (AUC) after sucrose intake compared with placebo in the normal (T0-60 min 3,232±356 vs 3,295±312 vs 3,652±454 mg.min/dL; p=0.016) and pre-diabetic subjects (T0-60 min 2,554±395 vs 2,472±280 vs 2,888±502 mg.min/dL; p=0.048). There was no statistically significant difference of changes in insulin levels between the placebo and black tea groups (p>0.05). No significant differences in adverse effects were observed with the placebo, low dose and high dose of BTPP groups.

    CONCLUSION: Black tea consumption can decrease postprandial blood glucose after sucrose intake.

    Be well!


  10. JP Says:

    Updated 07/10/17:


    Randomized controlled trial of the effects of consumption of ‘Yabukita’ or ‘Benifuuki’ encapsulated tea-powder on low-density lipoprotein cholesterol level and body weight.

    Background: Previous studies have reported controversial results for the association between green tea consumption and low-density lipoprotein (LDL)-cholesterol and body weight.

    Objective: The objective of this trial was to determine the effects of two kinds of green tea on LDL-cholesterol and body weight.

    Methods: We randomly assigned 151 participants (98 men, 53 women) aged 30-70 years into three groups: Yabukita green tea group, Benifuuki green tea group, or placebo group. Participants consumed 1.8 g/day of green tea extract powder or placebo for 12 weeks. The primary outcomes were LDL-cholesterol level and body weight, and the secondary outcomes were risk factors for cardiovascular disease.

    Results: Both Yabukita and Benifuuki green tea significantly lowered LDL-cholesterol. The magnitudes of the lipid-lowering effect of both types of tea were significantly larger than that of placebo. No differences with respect to changes in LDL-cholesterol were observed between the Yabukita and Benifuuki green tea groups. Neither Yabukita nor Benifuuki green tea had any effect on body weight and no difference was observed among groups regarding changes in body weight.

    Conclusion: Both Yabukita and Benifuuki green tea lowered LDL-cholesterol, and the lipid-lowering effects of these two green teas were not different. Neither tea lowered body weight.

    Be well!


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