Posts Tagged ‘Green Tea’

International Tea Day is celebrated annually on December 15 to highlight the effect of the trade of tea globally on the economy, workers, farmers, and society.

With this day in front of us, let’s look at some of the beneficial effects of green tea.

All teas come from the same plant, Camellia Sinensis, but are prepared using different methods. Green tea, which represents roughly 20% of the world’s tea production, is produced by steaming and frying the leaves and then drying them.

Tea has been utilized for therapeutic purposes in China and Japan for many centuries. While many countries favor black tea, the production process for black tea has a huge impact on its chemical composition. During the process of fermenting the leaves, the bioactive polyphenols are oxidized into pigment which may change their antioxidant properties. What’s more, many people like to consume black tea with milk, which additionally decreases the effectiveness of those bioactive components.

Green tea has been a staple of billions of people all over the world for centuries, yet only recently researchers have begun to examine its true benefits. As of late, the health promoting benefits of green tea and isolated green tea constituents have been under investigation. It should also be noted that adding green tea to the diet may cause other health concerns including adverse reactions with other prescription medication.

What makes green tea different?

The health-promoting effects of tea are primarily attributed to its polyphenol content, particularly flavanols and flavonols, which represent 30% of fresh leaf dry weight. When we look at the composition of green tea and black tea, it is very similar for the most part. The biggest compositional difference between them lies in their content of phenolic compounds and the oxidized phenolic compounds. While green tea is rich in phenolic compounds (six times more compared to black tea), black tea, due to its production process, has more oxidized phenolic compounds.

What do people use it for?

Tea is one of the most popular beverages consumed worldwide. Compared to other types of tea, the most significant effects on human health have been observed with the consumption of green tea. Green tea, as a beverage or dietary supplement, is promoted for a wide variety of conditions including relief from digestive symptoms and headaches and promoting weight loss.

Epigallocatechin-3-gallate (EGCG), which is a component of green tea, has been studied for its protective effects against heart disease and cancer. People have reported using green tea orally for the treatment or prevention of multiple conditions such as:

• depression
• certain types of cancer
• human papilloma virus (HPV)
• genital warts
• urinary tract infections
• hypertension
• Crohn’s disease
• ulcerative colitis
• osteoporosis
• cardiovascular disease
• diabetes

Gargling with green tea is also used for the prevention of colds and flu.

Green tea products are also used for some oral conditions. Green tea extract mouthwash is used for postoperative pain associated with tooth extraction. Green tea chewable candies are used for gingivitis. Topically, green tea creams/lotions are used as a treatment for genital warts and to prevent skin damage from ultraviolet radiation and other environmental causes.

Does it work?

It is evident that there is more study needed to say with confidence that green tea is effective for certain conditions. Using the data from the studies conducted so far, we can group the effectiveness of green tea into three categories:

• likely effective (there is high level of reliable clinical evidence)
• possibly effective (there is some clinical evidence supporting its use, but the evidence is limited by quantity, quality or contradictory findings)
• insufficient evidence to rate effectiveness (not enough scientific evidence)

The following table categorizes the proposed uses for green tea into the three categories:

Is it safe to use?

Green tea contains tannins. Tannins can interfere with the absorption of iron, so try not to drink green tea with an iron-rich meal and leave at least one hour before drinking tea after an iron-rich meal.

Green tea is also a source of caffeine, so it is important to take that into consideration when consuming it regularly. Drinking green tea is LIKELY SAFE for most healthy adults when consumed in moderate amounts (about 8 cups per day).

Green tea extract can cause stomach upset and has been reported to cause liver and kidney problems in rare cases, so it is important for patients with liver and kidney disorders to consult their doctors before starting regular consumption of green tea. There is limited clinical evidence that shows green tea has some safety concerns or significant adverse effects when consumed in high doses or for a long time.

Drinking green tea may be safe during pregnancy and while breastfeeding when consumed in amounts up to 6 cups per day (no more than about 300 mg of caffeine). Drinking more than this amount during pregnancy may be unsafe and may increase the risk of negative effects. Consumption of caffeine in amounts over 300 mg daily is associated with a significantly increased risk of miscarriage in some studies. Pregnant women are advised to keep caffeine consumption from all sources below 300 mg daily. This is similar to the amount of caffeine in about 6 cups of green tea.  It is important to consider that green tea may increase the risk of birth defects associated with folic acid deficiency.

Caffeine passes into breast milk and can affect a breastfeeding infant. There is limited evidence that shows that green tea is considered safe in children and adolescents in amounts commonly found in foods and beverages. There has been no significant adverse effect in children and adolescents associated with daily caffeine intake of less than 2.5mg/kg.

Alternative green tea products:

With the increased awareness of healthy living, natural products are becoming more and more integrated into our daily lives every day. Due to the wide array of conditions that green tea extracts are being attributed to helping, there are many different forms of green tea extracts being sold online and in stores. The image below shows some different types of green tea extract products that are available on Amazon.

Final thoughts

The limited amount of research available on natural products makes it difficult to confidently recommend them for treatment or prevention of any conditions. It is crucial that we inform our doctors about any natural product or supplement that we take. While they may be natural products, they can, just like prescription medications, interact with other medications and cause undesired effects.

Unlike prescription medications, over-the-counter supplement manufacturers don’t have to get approval from the Food and Drug Administration (FDA) prior to putting products on the shelves, so it is important that consumers verify that they are getting what the label claims to be in the product. One way to ensure that is to check that the product has the “USP certified” or “Consumer lab certified” label on it. These organizations test and verify that the products actually contain what they claim on the label in the declared potency and amounts. It is important to note that the certification ensures the component and its quantity, but does not eliminate the potential risk of adverse effects or drug interactions, so it’s important to consult a physician or pharmacist to help make the best possible choice.

References:

• McKay JBB, KT. Kavanagh LJH, N. Sueoka MS, et al. Beneficial effects of green tea: A literature review. Chinese Medicine. https://cmjournal.biomedcentral.com/articles/10.1186/1749-8546-5-13. Published January 1, 1970. Accessed December 3, 2020.
• McKay JBB, KT. Kavanagh LJH, N. Sueoka MS, et al. Beneficial effects of green tea: A literature review. Chinese Medicine. https://cmjournal.biomedcentral.com/articles/10.1186/1749-8546-5-13. Published January 1, 1970. Accessed December 3, 2020.
• Green Tea. National Center for Complementary and Integrative Health. https://www.nccih.nih.gov/health/green-tea. Published October 1, 2020. Accessed December 3, 2020.
• Green tea. https://naturalmedicines-therapeuticresearch-com.proxy.lib.ohio-state.edu/databases/food,-herbs-supplements/professional.aspx?productid=960. Published August 5, 2020. Accessed December 3, 2020.

Picture reference:

https://pixabay.com/images/search/green%20tea/

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