Thursday, July 15, 2010

Green Tea for More Than Two Reasons

Image found here

I've noticed that lately tea and it's potential for health benefits has been getting a great deal of attention in the media. This report from the 2010 Alzheimer's Association International conference mentions the results of a study which hints that tea consumption may reduce mental decline:
July 12, 2010 (Honolulu, Hawaii) — Regular tea consumption may slow the rate of cognitive decline in cognitively normal older adults, but this protective effect does not appear to be related to caffeine, a large longitudinal study suggests. Presented here at the Alzheimer's Association International Conference on Alzheimer's Disease 2010, results from the Cardiovascular Health Study, which examined the relationship between consumption of tea and coffee and change in cognitive function over time, showed tea drinkers had lower average annual rates of cognitive decline compared with non-tea-drinkers, ranging from 17% to 37%.
Another study, conducted by Queen Margaret University, Edinburgh, Scotland, UK studied the effects of regular consumption of green tea on healthy subjects. The results were reported in 2009 and issued astonishing conclusions:
Conclusion: Our results has shown that short term consumption of commercial green tea reduces systolic and diastolic BP, fasting total cholesterol, %body fat and body weight suggesting a role for green tea in decreasing established potential cardiovascular risk factors. This study also suggests that reductions may be more pronounced in the overweight population where a significant proportion are obese and have a high risk of cardiovascular disease. Green tea consumption is cost effective, accepted by patients and has no reported side effects.
Well, now. It appears that it might be a good idea to start slugging down tea by the gallon. But is it really as safe as the Queen Margaret University article suggests? I seem to recall that not all experts agree on the completely benign nature of this beverage.

Here's a very thorough review of green tea made by the University of Maryland and reviewed as recently as 8/09. It does indeed confirm that consuming green tea has potential positive benefits for a lengthy list of health issues, such as atherosclerosis, high cholesterol, cancer, inflammatory bowel disease, diabetes, liver disease, weight loss and even tooth decay. How impressive is that?

But the article also goes into great detail to list the potential side effects and drug interactions possible for tea drinkers. Here's a small sampling, but please read this excellent article in it's entirety. It's well worth the time:


The use of herbs is a time-honored approach to strengthening the body and treating disease. However, herbs contain active substances that can trigger side effects and interact with other herbs, supplements, or medications. For these reasons, people should take herbs with care, under the supervision of a practitioner knowledgeable in the field of botanical medicine.
People with heart problems, kidney disorders, stomach ulcers, and psychological disorders (particularly anxiety) should not take green tea. Pregnant and breastfeeding women should also avoid green tea.
People who drink excessive amounts of caffeine (including caffeine from green tea) for prolonged periods of time may experience irritability, insomnia, heart palpitations, and dizziness. Caffeine overdose can cause nausea, vomiting, diarrhea, headaches, and loss of appetite. If you are drinking a lot of tea and start to vomit or have abdominal spasms, you may have caffeine poisoning. If your symptoms are severe, lower your caffeine intake and see your health care provider.

Possible Interactions:

If you are being treated with any of the following medications, you should not drink green tea or take green tea extract without first talking to your health care provider:
Adenosine -- Green tea may inhibit the actions of adenosine, a medication given in the hospital for an irregular (and usually unstable) heart rhythm.
Antibiotics, Beta-lactam -- Green tea may increase the effectiveness of beta-lactam antibiotics by reducing bacterial resistance to treatment.
Benzodiazepines -- Caffeine (including caffeine from green tea) has been shown to reduce the sedative effects of benzodiazepines (medications commonly used to treat anxiety, such as diazepam and lorazepam).
Beta-blockers, Propranolol, and Metoprolol -- Caffeine (including caffeine from green tea) may increase blood pressure in people taking propranolol and metoprolol (medications used to treat high blood pressure and heart disease).
Blood Thinning Medications (Including Aspirin) -- People who take warfarin, a blood thinning medication, should not drink green tea. Since green tea contains vitamin K, it can make warfarin ineffective. Meanwhile, you should not mix green tea and aspirin because they both prevent platelets from clotting. Using the two together may increase your risk of bleeding.
Chemotherapy -- The combination of green tea and chemotherapy medications, specifically doxorubicin and tamoxifen, increased the effectiveness of these medications in laboratory tests. However, these results have not yet been demonstrated in studies on people. On the other hand, there have been reports of both green and black tea extracts stimulating a gene in prostate cancer cells that may cause them to be less sensitive to chemotherapy drugs. Given this potential interaction, people should not drink black and green tea (as well as extracts of these teas) while receiving chemotherapy for prostate cancer in particular.
Clozapine -- The antipsychotic effects of the medication clozapine may be reduced if taken fewer than 40 minutes after drinking green tea.
Ephedrine -- When taken together with ephedrine, green tea may cause agitation, tremors, insomnia, and weight loss.
Lithium -- Green tea has been shown to reduce blood levels of lithium (a medication used to treat manic/depression).
Monoamine Oxidase Inhibitors (MAOIs) -- Green tea may cause a severe increase in blood pressure (called a "hypertensive crisis") when taken together with MAOIs, which are used to treat depression. Examples of MAOIs include phenelzine and tranylcypromine.
Oral Contraceptives -- Oral contraceptives can prolong the amount of time caffeine stays in the body and may increase its stimulating effects.
Phenylpropanolamine -- A combination of caffeine (including caffeine from green tea) and phenylpropanolamine (an ingredient used in many over-the-counter and prescription cough and cold medications and weight loss products) can cause mania and a severe increase in blood pressure. The FDA issued a public health advisory in November 2000 to warn people of the risk of bleeding in the brain from use of this medication and has strongly urged all manufacturers of this drug to remove it from the market.
These studies refer to a commercially produced green tea made from Camellia sinesis and may be referred to as a Chinese green tea. Other tea products found on your health food store shelf may contain very different ingredients which may have other health implications, especially for those of us with autoimmune disease. A very good example? Alfalfa tea and sprouts. The effects of alfalfa have been documented as detrimental to Lupus and other autoimmune disease patients. This from the National Institutes of Health:
Lupus-like effects have been associated with alfalfa use, including antinuclear antibodies in the blood, muscle pains, fatigue, abnormal immune system function, and kidney abnormalities. Therefore, people with a history of lupus (systemic lupus erythematosus) or a family history of lupus should avoid alfalfa supplements.
Any tea made from herbal supplements such as echinacea or any other supplement that promises to boost immune function should never be used without checking with your physician. Some studies have indicated that these supplements increase autoimmune activity.

Well. When ingested after some careful conversations with your doctor and/or pharmacist and with a healthy dose of common sense, it seems as though a few cups of garden-variety green tea, for many of us, may be indeed a healthy drink. One lump or two? Milk?



Anonymous said...

And in moderate amounts. Some of those warnings appear addressed at people who take green tea pills, or who slug it back by the jug instead of the cupful.

I love the one about pregnant and breastfeeding women. EVERYTHING is contraindicated for pregnant and breastfeeding women, so they don't have to do the studies (that someone would yell about, no doubt). Fortunately my doctors are sane - and a cup or two of green tea a day is just fine.

Unknown said...

You are absolutely right! Green tea is very good health and it has beeen proven by doctors also that regular intake of green tea makes you healthy. It has many health benefits and it tastes good also.