Black and Green Tea

By Rania Gollakner, BS, DVM, MPH

What is black and green tea?

Black and green teas are made from the leaves and buds of the tea plant, Camellia sinensis. Black tea is made from green tea leaves that have oxidized. This oxidation process results in decreased levels of catechins, the active ingredient in tea. Therefore, green tea has higher levels of catechins.

Catechins or polyphenols have been shown to possess strong antioxidant properties (see handout ”Antioxidants”), thus preventing damage to DNA, and reducing risk of cancer cell formation. Through their antioxidant activity, the catechins in green tea may also profoundly reduce inflammation of the liver and gastrointestinal tract, providing a potential benefit in enteritis and hepatitis in small animals of almost any cause. Black tea also contains theaflavins and thearubigins, which inhibit carcinogens and protect against oxidative damage. In humans, it is used as an anti-cancer agent and to lower blood cholesterol.

What are dietary supplements?

Dietary supplements are substances that can be used to supplement the diet, such as vitamins, minerals, amino acids, herbs, botanicals, enzymes, and probiotics. While many supplements are sold over the counter, they still contain ingredients that have biological effects that should be managed by your veterinarian. Follow your veterinarian’s directions and cautions very carefully as their directions may be significantly different from those on the label.

There are differences in how countries regulate supplements. In the United States, these substances are not as vigorously regulated by the FDA as other medications, which means they can be sold without the manufacturer proving their effectiveness, safety, and without a guarantee of consistent or accurately reported ingredients. In Canada, products that have been evaluated for quality, safety, and effectiveness by Health Canada and authorized for sale will have a license number on the label.

How effective is green/black tea?

Limited studies in animals have been performed, but there is anecdotal evidence that green/black tea works to supplement cancer treatment via antioxidant actions. In humans, epidemiological research suggests that regular consumption of green tea reduces the incidence of colon, pancreatic, and stomach cancers. Clinical trials using green tea in humans are limited in number.

How is green/black tea given?

Green/black tea is given by mouth in the form of dry tea leaves mixed into food. Supplements containing the active ingredients may also be given by mouth and typically come in the form of capsules.

What if I miss giving my pet the supplement?

If you miss a dose, give it when you remember, but if it is close to the time for the next dose, skip the dose you missed and give it at the next scheduled time, and return to the regular dosing schedule. Never give your pet two doses at once or give extra doses.

Are there any potential side effects?

Studies are limited for this supplement and therefore information regarding side effects is also limited. If using caffeinated green/black tea, side effects may include sleeplessness, nervousness, increased heart rate, and anxiety.

Are there any risk factors for this supplement?

Studies are limited for this supplement and therefore information regarding risk factors is also limited. While green/black tea is considered a food and is generally regarded as safe, contraindications for ingesting green tea in humans includes kidney disease, stomach or intestinal ulcers, heart disease, insomnia, glaucoma, and high blood pressure. Based on this, use green/black tea should be used cautiously in pets with these conditions.

Are there any drug interactions I should be aware of?

The following medications should be used with caution when given with green/black tea: antifungals, fluoroquinolone antibiotics, insulins, MAOIs, phenylpropanolamine, theophylline, or warfarin.

Vitamins, herbal therapies, and supplements have the potential to interact with each other, as well as with prescription and over the counter medications. It is important to tell your veterinarian about any medications (including all vitamins, supplements, or herbal therapies) that your pet is taking.

Is there any monitoring that needs to be done with this supplement?

There is no specific monitoring that needs to be done while your pet is taking this medication. Your veterinarian may monitor your pet to be sure that the medication is helping. Monitor your pet at home for side effects.

How do I store green/black tea?

Store loose tea in an airtight container, preferably it the refrigerator, and protected from light. For the manufactured supplements, there are many different manufacturers, so follow the storage directions on the label.

What should I do in case of emergency?

If you suspect an overdose or an adverse reaction to the medication, call your veterinary office immediately. If they are not available, follow their directions in contacting an emergency facility.

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