The Health Benefits of Green Tea
Green tea is a beverage that has been consumed for health benefits for thousands of years. Research over the last few decades has started to verify a number of these benefits. Green tea may help with:
- Colds and flu
- Weight loss
- Heart disease
- Mental health
- Alzheimer’s disease
Colds and Flu
With the recent spread of Covid-19 virus in the United States and the cold and flu season still in swing, any treatment that potentially decreases the incidence and severity of upper respiratory tract infections is worth exploring.
Catechins are one of the main antioxidants found in tea. Research suggests that taking catechins may decrease the incidence of upper respiratory tract infections. A trial in healthcare workers suggested that dosing catechins may halve the risk of getting sick (Furushima 2019).
A review on tea and catechins also found that they may be useful in preventing colds and flu. Data is suggestive that tea and tea catechins may decrease upper respiratory infections between one-third to over one-half (Furushima 2018).
Green tea and green tea supplements have been used in weight loss products for a number of years. While data has some inconsistencies, a recent meta-analysis showed that green tea supplements were beneficial for metabolic syndrome and obesity. The study found improvements in blood sugar and HDL cholesterol along with weight loss (Li 2019).
Other review studies looking at green tea for suppressing appetite or for maintaining weight loss didn’t show significance (Stuby 2019, van Baak 2019). Overall, we need better research. However, I think it is likely that green tea may have some benefits. While rare cases of liver damage have occurred with green tea supplements (Hu 2018), when used as a beverage, green tea is very safe.
A recent review looked at green tea consumption and risk of cardiovascular events and death (Chung 2020). While they state the strength of evidence is low to moderate, they showed that for every cup of tea consumed per day there was:
- 4% lower risk of heart disease mortality
- 2% lower risk of heart disease events
- 4% lower risk of stroke
- 1.5% lower risk of all-cause mortality
While benefits were modest, it’s worth noting that heart disease is still the number one killer in the United States. Drinking three cups a day would potentially lower heart disease deaths by over 10%.
There’s been a fair amount of interest in whether or not green tea has an impact on cancer incidence and mortality. There is a lot of data showing that green tea can impact cancer pathways (Wang 2020), but studies on cancer in human populations has again been somewhat mixed. From the evidence available, there may be a lower incidence of cancer with green tea, but they didn’t find a change in cancer mortality (Filippini 2020).
There’s also a possibility that the data could be mixed due to pesticide exposure from tea. It’s not unusual that tea is sprayed with pesticides and the leaves have a large surface area for exposure (Abd El-Aty 2014). While this is pure speculation, it would be interesting to see if organic tea, or tea documented to be lower in pesticides might yield more consistent results for benefitting cancer.
A recent analysis of green tea consumption and risk of depression also showed positive effects. From all the studies, they concluded that 3 cups a day of green tea was enough to decrease risk of depression by 37% (Dong 2015).
The anti-depressant effects of green tea are likely mediated through a number of pathways. Tea exerts anti-inflammatory and antioxidant effects. In addition, tea increases dopamine signalling. Tea also helps increase brain derived neurotrophic factor, a growth factor for brain cells (Rothenberg 2019).
Data is also starting to accrue that green tea may play a role in prevention and treatment of Alzheimer’s disease. Green tea has documented anti-inflammatory effects along with protective effects for brain cell damage and swelling (Cascella 2017). While more studies are needed, a clinical trial showed that the equivalent of 2-4 cups of tea a day was able to improve cognitive performance in patients that had early dementia (Ide 2014).
Green tea appears to have a number of different health benefits. Generally, if a person wants to get benefits from tea I recommend drinking between 2-4 cups per day. Be aware that you can drink too much tea, as tea has higher levels of aluminum and fluoride. Cases of bone damage from high tea consumption (1-2 gallons a day) have been documented (Izuora 2011). I also recommend choosing an organic variety to decrease risk of pesticide exposure.
Tea is something I enjoy on a daily basis. It’s nice to know that it likely contributes significant benefits to my overall health as well.