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.