Saturday, December 27, 2014
Researched for centuries and used as remedies in numerous cultures around the world, tea should be a daily beverage in everyone's diet. In this post, we'll discuss the latest research regarding the numerous benefits of green tea consumption including weight loss, influenza prevention, cancer, blood pressure, and Alzheimer's disease.
A recent study in the Journal of Nutrition found that green tea, black tea, and oolong tea had significant effects on weight loss. In this study, mice were fed high-fat/high-sucrose diets which were supplemented with polyphenol extracts (caffeine-free) from green tea, black tea, or oolong tea. For all three tea types, mice who received tea supplementation lost significant weight and visceral fat. Interestingly, mice fed the green tea variety reduced their food intake ~10%. The authors believe this could be attributed to the higher levels of ECGC found in green tea compared to the other teas.
Additionally, the study demonstrates that the mechanism of action between green tea and black tea is most likely different. For example, EGCG from green tea is believed to work primarily at the liver where it increases lipid oxidation and thermogenesis. On the other hand, black tea polyphenols may be acting primarily at the pancreas where it inhibits pancreatic lipase which results in decreased lipid absorption. Therefore, drinking both types of tea could help you combat obesity through two separate mechanisms.
It is important to note, however, that the optimal dosing of green tea (and most other herbs) for effective weight loss in humans is currently unclear. There are numerous benefits of tea, and there is no doubt that tea consumption certainly does far more good than harm when it comes to weight loss (unless you are using far too much cream and sugar).
Green tea (as well as many other herbs) is known to possess antiviral properties. An observational study was recently published which describes the association between green tea consumption and incidence of influenza infection among Japanese children between the ages of 6 and 13. The results indicated that children who drank more than 6 cups per week were roughly 40% less likely to catch the virus compared to children who consumed 3 or fewer cups per week. The data showed that consuming 1-5 cups of green tea per day can significantly help in the prevention of influenza infection in children.
A relatively recent clinical trial demonstrated the effects of green tea catechins and theanine on preventing influenza infection of healthcare workers in facilities for the elderly. In this study, 98 healthcare workers received capsules containing green tea catechins and theanine while 99 workers received placebo. After five months during the flu season, only 4 workers receiving green tea supplements became infected which was significantly lower than the placebo group where 13 workers became infected. Although this is a relatively small sample size, and this is a correlation (not causation) study, the study nevertheless indicates that green tea supplementation may be effective at preventing influenza infection.
A recent systematic review and meta-analysis looked at fourteen different randomized controlled trials of the effects of green tea or green tea extract on blood pressure among overweight and obese adults. The meta-analysis determined that for overweight and obese adults, it appears that either green tea consumption or green tea extract supplementation can result in a small but significant reduction in systolic and diastolic blood pressure. However, the authors warn that higher quality trials with larger sample sizes are required to confirm the efficacy of this supplementation on blood pressure in order to make safe but effective recommendations.
A recent study describes the effects of green tea enriched rye bread on blood pressure and weight loss in obese adults. In this study, 55 obese men and women went on an 8-week low-calorie diet followed by a 12-week weight maintenance phase where one group consumed rye bread and the other group consumed rye bread enhanced with green tea extract. There were no significant differences in terms of weight loss, cholesterol, triglycerides or waist circumference. However, the group that consumed the green tea extract bread did lower blood pressure.
I am not sure why the authors were interested in a bread formulation of green tea…look up the citation for more info if you’re curious. Nevertheless, adding green tea components to their diet significantly lowered their blood pressure.
One of the theories of cancer development and tumor recurrence is the stem-cell theory which states that mutations in stem cells is what leads to proliferation of mutated daughter cells. This theory helps explain why certain cancers have a high tendency to recur after a period of time (colon cancer for example) since chemotherapy appears to kill the primary tumor, but the mutated stem cells remain alive and continue to produce mutated daughter cells. A recent opinion article states that based on previous studies, flavonoids (from green tea and other herbs) appear to have the ability to suppress stem cell markers and properties and can allow these mutated stem cells to be more sensitive to standard chemotherapy. However, more research is required before making any definite claims. Additionally, green tea has been shown to negatively interfere with boron-based chemotherapeutics, so always discuss with your doctor if your supplements/diet interfere with your medication.
Many studies suggest that good diet and exercise can help reduce the risk of neurodegenerative diseases such as Alzheimer’s. Recently, scientists tested the effects of dietary EGCG (green tea catechin) and exercise on an Alzheimer’s disease mouse model. The results showed that both dietary EGCG and exercise (separately or combined) improved nest building and maze performance as well as lowered amyloid-B levels in the cortex and hippocampus. In conjunction with previous epidemiological and clinical studies, these results suggest that green tea consumption and exercise may certainly help prevent and/or slow the progression of Alzheimer’s disease.
Dangers and health concerns
Green tea is no doubt healthy, but it certainly has its dangers. The numerous phytochemicals in green tea (and other herbs/plants) may interfere with prescription and over the counter drugs such as warfarin and simvastatin, making them more or less potent. Therefore, it is important to consider what meds you are taking, and if there are risks involved with supplementing your diet with green tea (or other herbs like gingko biloba and ginseng). It’s also been shown that high doses of green tea extract can cause liver damage, so please always drink and supplement in moderation!
Have thoughts or questions? Let us know in the comments section!
 Heber et al. J Nutr. 2014 Sep;144(9):1385-93.
 Xu et al. Food Funct. 2014 Nov 28. [Epub ahead of print]
 Park et al. J Nutr. 2011 Oct;141(10):1862-70.
 Matsumoto et al. BMC Complement Altern Med. 2011 Feb 21;11:15.
 Li et al. J Hypertens. 2014 Dec 4. [Epub ahead of print]
 Bajerska et al. J Med Food. 2014 Dec 10. [Epub ahead of print]
 Sak et al. Curr Stem Cell Res Ther. 2014 Nov 26. [Epub ahead of print]
 Walker et al. J Alzheimers Dis. 2014 Oct 15. [Epub ahead of print]
 Webra et al. Curr Pharm Des. 2014 Oct 13. [Epub ahead of print]