Once you go green, you could always go black. (Photo by mckaysavage)
Green tea is all the rage these days, but there are some areas where black tea simply performs better.
One such area has to do with superoxide dismutase (SOD), an enzyme that repairs cells. Superoxide dismutase reduces the damage done to cells by superoxide, which is the most common free radical in the body. In addition to this antioxidant effect, SOD acts as an anti-inflammatory and is also involved in the production of skin cells.
In short, superoxide dismutase is a good thing. Even better is that tea, especially black tea, seems to increase its activity.
A study on rats by Zeyuan et al. reports:
During a 75 day feeding experiment of rats consuming diets with addinged green tea (GT), black tea (BT), and their water extracts (GTWE, BTWE), blood glucose was significantly decreased in all experimental groups, by averages of 23.9% in GT and GTWE and by 22.8% in BT and BTWE; the blood triglycerides were significantly reduced, by 33.3% in GT and GTWE and by 25.0% in BT and BTWE.
The activity of superoxide dismutase was significantly increased, by averages of 117.0% in BT and BTWE and 90.8% in GT and GTWE. However, malondialdehyde was significantly decreased, by averages of 34.6% in BT and BTWE and 25.4% in GT and GTWE.
This indicated that the ability of green tea to reduce blood glucose and blook triglycerides was higher than that of black tea in the aged rats but that the antioxidative ability of black tea was better than that of green tea in the aged rats.
What the above means is that while green tea was very effective in increasing SOD activity (almost a 100% increase), black tea was even more effective. Clearly, while the fermentation process removes some of the catechins in tea, it has some beneficial consequences as well.
Note that green and black tea also had positive effects on blood glucose levels, triglycerides and malondialdehyde.
For diabetics or those thinking of adding tea to their diet to help with weight loss, these results look quite promising. Reduced triglycerides from tea consumption is also good news. Here green tea wins, but black tea performed pretty impressively too; one third reduction for green tea and one fourth reduction for black tea. Nothing to sneer at. Malondialdehyde, which is a product of lipid peroxidation that is mutagenic and carcinogenic, was reduced more by black tea than green tea, although both showed significant reductions.
One thing to keep in mind is that the amounts used in this study were higher than the average tea consumption. The average tea drinker consumes about 6 grams of tea per day, which is equal to 3 tea bags.
The rats in the study, on the other hand, consumed 5, 10 and 20 times the human dose. SOD activity increased with the dosage in both green tea and black tea groups. However, even with the lowest dose of brewed black tea, which was only 5 times more than the average human consumption, SOD activity almost doubled; the larger doses did increase it even further, but not as significantly. When black tea leaves were mixed in the rat chow instead of feeding them brewed black tea, the effects were similar.
Green tea behaved somewhat differently. With brewed green tea, the lowest dose increased SOD only slightly, but the middle dose was more than twice as effective as the lowest dose. The highest dose didn't improve SOD further than the middle dose. When green tea leaves were consumed with the feed, the middle and high doses more than doubled SOD activity, but the lowest dose had only a slight effect.
Applying these findings to humans means that in order to get optimal results, you'd have to consume 60 grams of green or black tea (i.e. the middle dose), which is equal to a respectable 30 cups of tea per day. Unfortunately increases in bladder size were not studied.
Still, the results are impressive, and drinking 2-10 cups of tea (or taking a tea extract supplement) will very likely have at least some beneficial effect.
And if Earl Grey is more your cup of tea than Japanese sencha, these results are something you can relate to all your trendy friends who are hating on old-fashioned black tea for no good reason.