The Experts in Functional Medicine
Functional Medicine Florida

Green Tea and EGCG

This is Part 2 of the Green Tea Series. Here’s Part 1

In the first part of our series on green tea, we discussed the powerful compound found in the drink — polyphenol (-)-epigallocatechin-3-gallate, better known as EGCG, which can reduce inflammation and oxidative damage in the body.

EGCG exerts its near-miraculous benefits through scavenging reactive oxygen species (ROS), stimulating anti-oxidant enzymes and multiple other pathways. It even has anti-tumor effects.

Epithelial growth factor receptor (EGFR), which is thought to be a major driver in the immuno-oncology world, is inhibited by EGCG.

I have read several studies using supra-physiologic doses of EGCG to help treat certain diseases — doses that could never be ingested and are given in IV form.

I’ve discovered two studies that looked at the amounts of green tea that can be reasonably ingested through a regular diet.

In one paper, published in 2017 in BioMedicine & Pharmacotherapy, the effects of dietary EGCG in mice that had developed diabetes mellitus (DM) secondary to a high-fat diet were evaluated. The authors theorized that the activity of EGCG is through its interaction with nuclear factor erythroid 2-related factor (nrf2). Nrf2, in turn, contributes to the regulation of the heme oxygenase-1 (HO-1) axis — a potent anti-inflammatory pathway. The EGCG, from dietary green tea, may reduce plasma glucose levels and help alleviate complications of DM by decreasing or slowing the formation of advanced glycosylation end-products (AGEs).

The most well known of these advanced glycosylation end-products is hemoglobin A1C. AGEs are the end result of the body trying to deal with chronically elevated glucose or blood sugar. The glucose is attached to a protein, such as hemoglobin. This gets the glucose out of the blood stream, but permanently damages the hemoglobin, or any protein, it is attached to. AGEs develop at any glucose level, but are much more significant when the glucose is over 100.

The authors studied three groups of mice. All had diet-induced diabetes, or what is commonly called Type II or adult-onset diabetes:

Group 1: High-fat diet, supplemented with EGCG.

Group 2: High-fat diet, no EGCG.

Group 3: Low-fat diet, no EGCG.

Despite the poor diet, Group 1 showed significantly reduced weight gain, lower plasma glucose levels and lower insulin levels. The EGCG supplementation showed lower levels of AGEs in the blood and the liver, as well as a decrease in the number and functioning of RAGEs – the receptors for advanced glycation end-products (AGEs).

All of these beneficial findings are through the interaction of EGCG with the nrf2 pathway. The nrf2 pathway is also activated by sulfurophanes, which are found in high concentrations in blueberries.

In another study, published in 2022 in Biomedical Reports, the researchers examined green tea use in adolescents with mild stuttering symptoms. They noted that green tea and its polyphenolic compounds have been shown to have a positive impact on people with psychological issues.

For their researchers:

  • 30 teenagers drank 6 cups of green tea per day for 6 weeks.
  • 30 teenagers drank no green tea.

The teens who drank green tea had decreased levels of stress hormones such as cortisol, acetylcholine and other corticosteroids. They also didn’t stutter as much and overall had less anxiety. No such results were seen in the group that didn’t drink the tea.

I’ve discovered two studies that looked at amounts of green tea that can be reasonably ingested through a regular diet.

Caffeine intake with resultant headaches, and jittery or anxious feelings: Green tea has much less caffeine than coffee or certain sodas, though, so personally, I have not seen this to be an issue. If you are especially sensitive to caffeine, of course, do not consume it later in the day or perhaps try decaffeinated green tea.

Green tea may affect blood thinners: Green tea does contain a relatively small amount of vitamin K, which participates in the clotting cascade. This would be an issue only for those taking coumadin, as there are no routine labs for the newer “blood thinners.”

Patients on coumadin therapy usually get regular bloodwork to determine if they need adjustment. The key is to be consistent, with the same precautions that are given to patients on coumadin when it comes to eating leafy green vegetables, which are high in vitamin K.

I don’t have my own children, but have a number of nieces and nephews. I really can’t imagine getting a teenager, or an adult, to do something (drink green tea or anything else!) 6 times per day for their health.

In our next article in the green tea series, we will discuss how to increase the EGCG in our diets.