Green, Oolong, Pu'Erh or Black, All Teas May Help Keep Fat in Check. 750ml of Tea Per Day Could Ward Off Some of Your Holiday Weight Gain.

Image 1: Though color does matter to some extend, the most important thing appears to be that you drink your tea, whether it is green, black, white or well... pu-erh ;-)

Christmas time is approaching and my personal experience tells me that for many of my fellow human beings Santa has more than just iPads, iPhones and iPods in his gunnysack. The two, three or more pounds of body weight, Santa, or rather the festivities in his honor (unfortunately most people have forgotten that we are actually celebrating the birth of Jesus Christ) leave behind on their hips are yet mostly unwanted, so that the results of a recent study which was conducted by scientists from the National Hsinchu University of Education and the National Taiwan University may come pretty handy (Huang. 2011), especially for those of you who plan on having some "healthy" low sugar, but high fructose junk-food over the holidays.

Tea in lieu of hot wine punch could ward off your holiday weight gain 

In their 12-week study, Hsiu-Chen Huang and Jen-Kun Lin fed a group of initially healthy five-weeks-old male wistar rats (body weight: 150-200g) either a standard rat chow (Purina, Ralston Purina, St. Louis, MO) or a chow that consisted of 60% fructose and 40% of the chow.  Now, the latter group was again divided into a fructose control group and 4 experimental groups, where 4% of the standard chow were replaced by ground green, oolong, black or pu-erh tea leaves.

Figure 1: Catechin content of the leaves of green, oolong, black and pu-erh tea.

The scientists' reasoning was that the addition of the catechin-rich tea leaves (cf. figure 1) to the chow would ameliorate the detrimental effects of the high-fructose diets on blood lipids and other measures of metabolic health. Now, the whole rodent vs. human data aside, you are probably not willing to eat tea leaves, are you?

If we do yet assume that the main effect is induced by the "active ingredients" of the leaves and take the catechin content as a measure of how much of that we would have to ingest, eating the whole leaves is probably not even necessary. With their daily food intake of ~27.5g the rodents got roughly 46mg of catechins (calculated for the green tea).

That in turn would equal a dose of 153mg/kg (this calculation takes the weight gain into account) for the rats and 25mg/kg for a human being (cf. my article on human equivalent doses). So, if you weighed 80kg you would have to get 2g of catechins, which is the equivalent of 7.5 mini-cups of 100ml tea each brewed from 1g of tea (the last step in this calculation is based on USDA data from 2007).

Figure 2: Body weight of rats fed either the 40% fructose diet or the same diet enriched with 4% of tea leaves from green, black, oolong or pu-erh tea (data adapted from Huang. 2011)

But let's forget the math and the speculations about whether or not the results are going to translate to human beings for a moment and just have a look at the ameliorative effect the different types of tea had on the weight gain of the high fructose fed rats in the course of the study period. In that, it was not the catechin-laden green tea which had the most profound anti-obesity effect, but the highly oxidized black and the oxidized and fermented pu-erh teas.

Gaining the least weight does not necessarily mean having the "best" blood lipids

Interestingly, a different picture emerges, when we focus exclusively on the blood lipids, where the green tea leaves produce a lipid profile of which current medical "wisdom" tells us that it is the "most beneficial" one ;-)

Figure 3: Relative changes in serum lipid levels due to fructose feeding and fructose + tea leave feeding (data calculated based on Huang. 2011)

As a studious student of the SuppVersity, you will probably already be thinking about possible underlying mechanisms of these anti-obesity and anti-hyperlipidemic effects of the different types of tea leaves. Well, part of those are probably mediated by an old acquaintance: 5' AMP-activated protein kinase or AMPK.

Figure 4: Relative changes in AMPK phosphorylation and fatty acid synthethase in rats in response to feeding with 4% of black, green, oolon or pu-erh tea; my quantification on the left, original blots on the right  (data calculated based on Huang. 2011)

In view of the fact that Huang and Lin were either to lazy or did not consider it necessary to quantify their immunoblots (figure 4, right), I used a standard image processor to come up with the data in figure 4. Since this is obviously not very reliable, I also included the original blots so that you can convince yourselves that both the increase in AMPK phosphorylation, as well as the amelioration of the fructose induced increases in fatty acid synthethase activity correlate with the effects the different types of teas had on lipid metabolism of the rats.

Green, Black, Olong, Pu-Erh? Which tea to chose?

If we take a final look at the "whole picture", it appears that the exotic pu-erh tea would be the tea of choice, when you totally discard taste, price and whatever other factors may influence your choice. After all, it is was exactly as effective in ameliorating the weight gain as the black tea, induced an impressive +244% increase in AMPK phosphorylation and had what I, contrary to the medical establishment, would consider the "optimal" effect on the lipid profile of the rodents (a profound decreases in triglycerides, even below the level of rats fed the normal chow, and a +11% increase in HDL over the control diet despite high fructose feeding). The "classics", black and green tea, on the other hand, share a close and still notable second place, while the fancy oolong tea appears to be the least effective in this quartet of natural health promoters, the potency of which, and this is something I cannot emphasize enough, can hardly be explained based on their catechin content alone (cf. figure 1) and thusly renders the use of respective abstracts for the same purpose more than questionable.

Chinese Black, Green & Olong Tea is NO Health Beverage. Lead, Chromium, Cadmium and Potentially Toxic Levels of Manganese + Endocrine Disrupting PFCs Are the Rule

"Pesticide pollution: Chinese tea may not be safe to drink," this is what you could read on the website of Greenpeace in 2012, already and obviously this has not changed over the last 2 years | read more

I've actually written about the problem with toxins in tea, specifically green tea from China, before and I wouldn't be too sure, whether bad news like the previously reported "-20% Reduction in Green Tea From Just 5 Cups a Day" (learn more) could not possibly be a result of heavy metals and/or other toxins, as well. This and the fact that the data I am going to talk about in the following paragraphs is based on analyses of 43 representative tea products (including 18 green, 12 Oolong, and 13 black teas) from 7 main tea production provinces in China makes today's SuppVersity article relevant for everyone who consumes green tea from China or of unkown origin - China is the cheapest, so guess, where it's from ;-)

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Apropos "Guess where it's from!", if I had to guess, I would say that 99% of the black, green and olong tea extracts in green tea, fat burner, pre-workout, anti-oxidant, and other commercially available supplements will be from China. The fact that cadmium (Cd), inorganic and thus toxic chromium (Cr) and lead (Pb) were present in samples from Zhejiang, Fujian, Yunnan, Anhui, Hunan, Guangdong and Taiwan is relevant for ~95% of the SuppVersity readers.

You think that's an old hat? Well, what about the perfluorinated compounds (PFCs) the researchers, who are by the way working for the China Ministry of Agriculture and thus certainly not interested in making Chinese tea look like a poisonous swill, detected in all samples. The concentration of these emerging and ubiquitous organic pollutants in the samples varied. In view of the already established negative health effects of which Eriksen et al. (2009), Corsinia et al. (2012) and Posta et al. 2012) write that they encompass...

• 

  Would all commercially available teas have to be labeled like this? A previous study which found also Aluminum & Arsenic in tea bags, would suggest just that | read more

  thyroid dysfunction, 
• preeclampsia,
• increased risk of high cholesterol
• increased risk of cancer, 
• liver dysfunction, 
• disruption of the immune system,
• disturbances of the endocrine (=hormone) system, 
• developmental delays, and
• fertility issues

...which could potentially occur with chronic exposure to comparatively low amounts of these toxins, this is certainly disconcerting.

PFCs are everywhere: Due to their toxic effects in humans and other organisms, PFCs were added to the list of banned chemicals in the Stockholm Convention on Persistent Organic Pollutants in 2009 (Ma and others 2012). Perfluorooctane sulfonate (PFOS) and perfluorooctanoic acid (PFOA) have been detected in animals and water samples from rain, river, wastewaters, and sea. They are present in plants and crops, including all twenty foodstuffs that were examined in 2004 in Great Britain by Gem et al. in 2006. PFCs are present in wheat, oats, potatoes, and maize (Stahl. 2009) and their concentration is the highest in plants / crops that grow in or close to the ground - including the peeled edible parts of carrots, potatoes, and cucumbers.

If you look at the maximal heavy metal content (individual circles in Figure 1) you will see that eventually, even the high manganese content of up to 240mg/100g could become problematic.

Figure 1: Box plots of Cd, Pb, Cr, Cu, Zn, and Mn contents in 43 tea products from south China. The central solid line within each box is the median, and the bottom and top of each box represent the 25th and 75th percentiles, respectively (Zhang. 2014); the values outside this range are plotted as individual outliers (o).

The upper tolerable intake level (UTI) of manganese is only 11mg for an adult. If you adhere to the recommended 3g per 150ml water you would thus exceed the UTI by ~30% with with the amount of tea you'd put into only 2 cups! That's bad news, even if the hot water does not extract the total amount of manganese. It is after all not unlikely that toxic effects such as the Parkinson-esque shaking (tremors), which is supposedly a direct result of the neurotoxicity of manganese (Dobson. 2004),  can occur with the chronic ingestion of subtoxic doses in the 5mg/day range, as well.

And while the combination of cadmium, lead and chromium is etching away your brain and nervous system, the PFCs, which were detected in form of PFOS in only 6 samples and in form of PFOAs in 33 samples, will launch an attack on your endocrine system. Unfortunately, there is no reliable information on whether or not chronic exposure to teas with  250ng/kg dw of this endocrine disruptor will or will not have permanent negative effects on your health.

Table 1: Contents of PFOA and PFOS according to origin (left) and type (Zhang. 2014)

What we do know, though is that Oolong teas were 15x more frequently contaminated than green tea. Apropos, if you look at the data in Table 1 you will see that the tea producers in the Anhui Province are either most generously intoxicating their produce with PFC-containing products, or plant their tea plants right next to some industrial complex. Here, more than 50% of all tested samples contained both PFOA and PFOS.

Green still the "greenest": In Germany "green" mean ecological and "clean" and at least for the 43 batchs of green, oolong and black tea this association holds for Chinese teas, as well. The results of the study at hand clearly show that black teas had - on average - higher amounts of heavy metals and PFCs in them than oolong or green teas. This doesn't change the fact, though, that the major and potentially toxic manganese offender in the study was a batch of green tea (unfortunately, Zhang et al. don't disclose the province it was from). So, don't make a mistake: Green tea is not generally a safe choice - at least if it's from China.

Bottom Line: Chinese tea is certainly not your best choice! I would not go so far as to say that you must avoid it like a plague, though. Firstly, we don't really know if the heavy metal and PFC levels in the produce from other countries are much lower. Secondly, only few of the samples may be considered "officially" hazardous to your health. And thirdly, there is insufficient data on both, the amount of heavy metals (specifically manganese) and PFCs that will leach out of the leaves, into your tea and make it from there across the gut lining into your blood stream, as well as their potential long-term consequences.

The initially mentioned "Drinking Green Tea Reduces Your Testosterone Levels" study, is yet only one out of countless "surprisingly" disappointing studies with green tea and green tea supplements the negate results of which could potentially be ascribed to the presence of heavy metals or PFCs in the green tea / green tea extracts that were consumed in the study. So, maybe, but just maybe, you want to take a brief look at the back of the next bag of green, oolong and black tea you buy to check, whether it's from China?

References:

• Dobson, Allison W., Keith M. Erikson, and Michael Aschner. "Manganese neurotoxicity." Annals of the New York Academy of Sciences 1012.1 (2004): 115-128.
• Ma, Jin, et al. "State of polybrominated diphenyl ethers in China: An overview." Chemosphere 88.7 (2012): 769-778.
• Stahl, T., et al. "Carryover of perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS) from soil to plants." Archives of environmental contamination and toxicology 57.2 (2009): 289-298.
• Zheng, H. et al. "Analysis of Trace Metals and Perfluorinated Compounds in 43 Representative Tea Products from South China." Journal of Food Science (2014). Accepted Manuscript. doi: 10.1111/1750-3841.12470