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Green tea health risks:
Could green tea actually be bad for you?


Green tea has received a lot of positive media attention in recent years. But is it really good for everyone?

Not necessarily.

There is a group of people for whom green tea may be hazardous. And given green tea’s popularity these days, it’s critical to share this information with anyone interested in health.

Green tea has a wealth of research behind it demonstrating a number of health-promoting benefits including anti-inflammatory, anti-carcinogenic and antioxidant properties.

Many of green tea’s benefits are due to its effects on the immune system, which is also where it can cause problems.

But before telling you how green tea impacts the immune system, let’s take a quick look at a simplified version of how it works.

Should you banish this harmless-looking substance from your pantry?
Should you banish this harmless-looking substance from your pantry?

A primer on the immune system

The immune system is composed of white blood cells, which are then differentiated into five different type of immune cells. One of those is a group of cells called lymphocytes.

Lymphocytes are then broken down even further into B cells, as well as T cells, which have their own subset of cells called T helper cells, T regulatory cells, cytotoxic T cells and T suppressor cells.

The immune system can be confusing, so rather than describe these cells in detail, I’ll use a real life example of how it works.

Let’s say you cut yourself with a dirty knife.  Bacteria penetrate your skin, engaging a first line of defense from our immune system called a macrophage (picture Pac Man).

Macrophages are like big, fat security guards wielding tiny billy clubs –- ineffective, but they’ll slow an invader down while they call on more sophisticated security guards.

When confronted with an invader, macrophages call on their friends, the T helper cells. The T helper cells tell the entire immune system through a series of chemical signals that there has been an invader that has crossed the barrier.

Specifically, the T helper cells call directly on two types of cells, cytotoxic T cells and natural killer cells, both soldiers with muscle that live up to their name and help attack and kill the bacterial invaders.

Once the bacteria have been killed, it is time for the immune system to call off the attack, which is the job of the T suppressor cells, who “suppress” the fight.

In the event that the bacteria is too powerful for the T cells, or if the T cells have a difficult time finding the invader, as in the case of a virus, the B cells are called to join in the fight. B cells make antibodies for a given invader based on instructions from the T helper cells.

In other words, if the T helper cells tell the immune system that the invader is a guy wearing an orange sweater, the B cells will create antibodies for a guy in an orange sweater, so that when they meet him, they can latch onto him and wave a flag, making it easier for the cytotoxic T cells and natural killer cells to find the invader.

But here’s what you really need to know:

  1. The initial T cell response is called a “Th1 response”.
  2. The secondary B cell antibody response is called a “Th2 response”.

In a healthy body, there is balance between the Th1 (T cell) and Th2 (B cell) parts of our immune system. And that’s the desirable state.

However, sometimes an imbalance of the Th1/Th2 system can be beneficial. For example, during pregnancy women have a tendency to shift towards a Th2 dominance, which is advantageous since a Th1 shift would induce rejection of the fetus.

Autoimmune disease: An immune system out of balance

Virtually all autoimmune diseases -– conditions where the immune system begins to attack self-tissue –- have either a Th1 or a Th2 dominance.

Put another way, autoimmune conditions generally have either a T cell upregulation and B cell suppression (Th1 dominant) or the opposite (Th2 dominant).

Th1 dominant: T cells up; B cells down

Th2 dominant: T cells down; B cells up

It’s imperative that people with autoimmune disorders maintain Th1/Th2 balance.

When the immune system is dysregulated and starts attacking body tissues, the more out of balance the immune system is, the more voraciously it will attack those tissues.

For example, in someone with rheumatoid arthritis, an autoimmune condition where the immune system attacks cartilage, the more out of balance the Th1/Th2 system is, the more cartilage destruction will take place.

When healthy foods are unhealthy

According to research, a number of natural compounds have a tendency to push either side of the Th1/Th2 balance.

Green tea is one such substance.  The active components of green tea have a tendency to push the Th2 system to be more dominant by inhibiting the Th1 side of the immune system.

Therefore someone with a Th2-dominant autoimmune condition (see table below) would be wise to stay away from green tea or products containing concentrated green tea (such as a green tea supplement), because it can upregulate an already dominant system and lead to more tissue destruction.

Conversely in someone with a Th1-dominant autoimmune condition, green tea would be beneficial because it inhibits the Th1 side of the immune system.

Another common example most people know of is the herb echinacea.

When people get sick with a cold or flu, echinacea helps boost the T cells (Th1 response) involved with the initial attack of a foreign invader.

However, in a Th1-dominant autoimmune condition, echinacea will likely make the condition worse and is therefore be something to be avoided.

Real world example

We had a patient come into our office and report that she took a single antioxidant capsule one night before bed and experienced an array of symptoms including heart palpitations, anxiety, “inward trembling” and insomnia.

The patient had been previously diagnosed with hypothyroidism, a low thyroid condition characterized by weight gain, fatigue, and depression-like symptoms.

The number one cause of hypothyroidism in the United States is an autoimmune condition called Hashimoto’s syndrome (or Hashimoto’s thyroiditis).

The patient’s symptoms after taking the antioxidant indicated an upregulated, or increased attack on her thyroid gland, which then released extra thyroid hormone into her system causing what are classically hyperthyroid symptoms.

When we looked at the ingredients in the antioxidant, it made sense.

Two of the main ingredients –- green tea extract and curcumin -– have been shown to push the immune system towards a Th2 dominance.  Given the symptoms she experienced after taking the antioxidant, we concluded that she suffered from a Th2-dominant Hashimoto’s autoimmune condition.

We surmised that the green tea and curcumin stimulated her already lopsided immune system into more aggressively attacking her thyroid gland.


There is no one food that is good for everyone.

We are all unique individuals, with different genetics, different biochemical needs and different reactions to ingested food.  Indeed, one person’s food is another person’s poison.

Many foods and supplements have a wealth of proven health benefits, but not for everyone.

If you have an autoimmune condition, some of these compounds can make you much better or much worse depending on your Th1/Th2 dominance.  You can talk with your doctor about running a lymphocyte panel to determine which dominance you have and then take the appropriate compounds to help push your immune system in the opposite direction.

But do not do this without the advice of a qualified medical professional! Pushing your system in the wrong direction can lead to further destruction of whatever tissue(s) your immune system might be attacking.

Green tea has a proven track record of benefits for the average person and, if you do not have an autoimmune condition, it seems wise to include green tea into your diet.

However if you have a diagnosed autoimmune condition, especially a Th2 dominance disorder, green tea might not be for you.

You may be wondering at this point whether you should clear your cupboard.

While there’s a basic list of common autoimmune conditions as a general guideline below, please be aware that this doesn’t always pan out in practice. I’ve found this along with some other practitioners.

When we run lymphocyte panels on people, we find some that differ from the clinical literature that categorizes people by Th dominance status. (In other words, the research says they should be one thing; but we find in fact that they’re the other.)

There is a lot we still don’t know about autoimmune conditions. If you see yourself on this list, don’t jump to any conclusions or self-diagnose, take the wrong supplement and make yourself worse (i.e. a Th2 dominant MS patient who demyelinates themselves by taking green tea).

Always check with a qualified practitioner.

Common Th1 dominance disorders

Organ-specific autoimmune diseases (Possible benefit from green tea)

  • Multiple sclerosis
  • IBD/Crohn’s disease
  • Type 1 diabetes
  • Hashimoto’s disease, Graves disease (thyroiditis)
  • Psoriasis
  • Rheumatoid arthritis
  • Heliobacter pylori induced peptic ulcer

Th1 stimulating compounds

  • Echinacea
  • astragalus
  • licorice root
  • beta-sitosterol
  • ashwaganda
  • panax ginseng
  • mushrooms (Maitake, Reishi, Shiitake)
  • chlorella
  • grape seed extract

Common Th2 dominance disorders

Systemic autoimmune diseases (Possible harm from green tea)

  • Allergies
  • Asthma
  • Chronic sinusitis
  • Many cancers
  • Hepatitis B and C (mixed Th1 and Th2)
  • Ulcerative colitis
  • Viral infections
  • Systemic lupus erythematosus
  • Helminth infections

Th2 stimulating compounds

  • Green tea
  • resveratrol
  • pycnogenol
  • curcumin
  • genistein
  • quercetin


Click here to view the information sources referenced in this article.

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