Camellia Sinensis (Green Tea) Benefits, Uses, Dosages & Side Effects

The common name for Camellia sinensis is Green Tea. It is one species of flowering evergreen shrubs/small trees in the Theaceae family.

The leaves and leaf buds of C. sinensis are used to make white, yellow, green, oolong, black, and dark teas like Pu-erh tea. [1]

Tea is one of the most popular beverages in the world. People drink green tea for numerous reasons and the use of Camellia sinensis in traditional Chinese medicine (TCM) dates back thousands of years.

In ancient times, it was used as a cooling agent to quench thirst, reduce phlegm, enhance alertness, refresh the mind, boost concentration, ease digestion, and promote urination. It was also used to treat headaches, sleepiness, heat stroke, and dizziness. [5]

Some of its most common uses today are for gastrointestinal disorders, cognitive function, normalizing blood-lipid levels, cardiovascular health, and weight loss. [2]

This article will discuss the Camellia sinensis plant, how it works in the body, common uses and health benefits, safety and side effects, and possible interactions with drugs and other supplements.

Green Tea Extract

Herbal Supplement

Alertness

Fat Loss

Cognition

How It Works:

• Increases energy, focus & mental function
• Boosts metabolism for weight loss
• Anti-oxidant & supports general well-being

Dosage:

Between 200 - 1000 mg per day

Safety:

Rated Possibly Safe

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Camellia Sinensis Description

Camellia sinensis plants can be found growing along the edges of forests in altitudes up to 9500 feet.

The plant is a woody, evergreen, mid-sized shrub that is normally cropped to about 5 feet tall to make harvesting easier. [3]

According to BioNET, Camellia sinensis plants develop oval, pointy-tipped, dark-green, finely-serrated leaves about 2 inches long, and five-petaled, white fragrant flowers. [3]

Green tea plants in commercial farming operations are prevented from flowering to keep the plant producing more leaf buds. The delicate first leaves and buds make the most desired teas and the plants are plucked up to five times yearly. [4]

There are four recognized varieties of Camellia sinensis: variant sinensis, var. assamica, var. pubilimba, and var. dehungensis.

Of those, C. sinensis var sinensis (Chinese Tea) and C. sinensis var. assamica (Indian Tea, Assam Tea) are primarily used for tea making. [3]

White, green, oolong, and black teas all come from the same plant. The degree of oxidation and how they are processed dictates the color of tea leaves and leaf buds.

A longer fermentation period yields a darker color because the plant material is more oxidized. The chlorophyll molecules that produce the green color are degraded which causes the leaves to darken. [4]

As a general rule, white tea is entirely unoxidized, green tea is minimally oxidized or not oxidized, oolong tea is moderately oxidized, and black tea is fully oxidized. [4]

Do not confuse Camellia tea trees with the source of tea tree oil, Melaleuca alternifolia. These plants are distinct and do not contain the same bioactive compounds. [1]

Herbal teas like those made with dandelion, chamomile, lavender, berries, and other plants do not contain the same bioactive chemical constituents that Camellia sinensis does.

While these “teas” may have various health benefits of their own, they are not true teas. Rather, they are non-tea plants used to make decoctions in water.

How Camellia Sinensis Works in the Body

Tea contain bioactive compounds called polyphenols. Polyphenols are compounds that contain multiple phenolic structural units.

Each phenolic hydroxyl group has the chemical formula C6H6O and consists of a phenyl group (?C6H5) bonded to a hydroxyl group (?OH). [1]

The Natural Medicines Comprehensive Database (NMCD) states, “Green tea is produced by steaming fresh leaves at high temperatures. This process inactivates certain oxidizing enzymes, but doesn’t decrease polyphenols.” [2]

The primary polyphenols in Camellia sinensis are known as catechins, including:

• Catechin gallate (Cg)
• Epicatechin
• Epicatechin gallate (ECg)
• Epigallocatechin
• Epigallocatechin gallate (EGCg)
• Gallocatechin
• Gallocatechin gallate (GCg) [2]

According to NMCD “Catechins in green tea range from 69 to 103 mg/gram of tea.” [2]

Plants are usually made up of 10-20% epigallocatechin-gallate (EGCg) and epigallocatechin catechins. The EGCg constituent accounts for 50-60% of the total catechin content. [2]

Camellia sinensis catechins are part of a class of polyphenols called flavonols. These catechin polyphenols are the most abundant and active in green tea.

This plant also contains several other types of polyphenols including flavandiols, flavonoids, and phenolic acids.

Some flavonoids include kaempferol, quercetin, and myricetin. Green tea leaf, leaf bud, and stem also contain:

• 2-4% caffeine
• A proteinogenic (protein building) amino acid called L-theanine
• Organic heterocyclic compounds called xanthenes
• Phytoestrogens including beta-sitosterol, matairesinol and secoisolariciresinol [2]

Mechanisms of Action

The NMCD reports dozens of mechanisms of action for Camellia sinensis observed in cell, animal, and human research. It has been shown to exhibit the following effects:

• Anti-arthritis effects
• Anticancer effects
• Anticoagulant/antiplatelet effects
• Antidiabetic effects
• Antidiarrheal effects
• Anti-inflammatory effects
• Antilipemic effects (reducing blood lipids)
• Antioxidant effects
• Antiviral effects
• Blood pressure effects
• Bone effects
• Cardiovascular effects
• Central nervous system (CNS) effects
• Cognitive effects
• Gastrointestinal effects
• Immunologic effects
• Respiratory effects
• Weight loss effects [2]

According to Shen-Nong, many of the benefits of drinking tea are linked to the antioxidant activity of polyphenolic compounds like EGCg.

Shen-Nong states that, “EGCG is considered the major component responsible for tea’s antioxidant activity, anti-aging properties, and cardiac health maintenance.” [5]

Uses for Camellia Sinensis

According to the NMCD green tea is used orally for:

• Cardiovascular disease
• Chronic fatigue syndrome (CFS)
• Diabetes mellitus
• Gastrointestinal disorders such as vomiting and diarrhea headaches
• Human papilloma virus (HPV)
• Hypotension (low blood pressure)
• Improving cognitive performance and mental alertness
• Non-alcoholic fatty liver disease (NAFLD)
• Osteoporosis (brittle, fragile bones) [2]

Camellia sinensis tea and supplements are also used orally for depression, ulcerative colitis, weight loss, genital warts, and perianal warts. It is also used for cervical dysplasia, Crohn’s disease, Parkinson’s disease, dental cavities/caries, kidney stones, and skin damage. [2]

Green tea has also been studied for a variety of cancers, including breast, cervical, colon, gastric, liver, lung, and prostate cancer. In traditional medicine, it is also taken for leukemia and skin cancer related to ultraviolet (UV) radiation and other environmental causes. [2]

Some people gargle with room-temperature green tea to improve symptoms of flu and colds. A liquid extract from this plant has been used in mouthwash for treating post-surgical pain after teeth extractions. [2]

Green tea leaves have been used topically in tea bags and poultices to soothe sunburn, treat “bags” under the eyes, stop tooth socket bleeding, and for headaches or tired eyes.

Some people chew the leaves for gingivitis, while others use it in a foot bath for athlete’s foot infections. [2]

Many of the purported benefits are based on traditional uses and anecdotal evidence. More research is needed to validate many of the health claims made about this supplement.

Camellia Sinensis Health Benefits

Camellia sinensis extracts have been studied extensively for decades for their health-promoting effects. Population studies have found a number of benefits linked to regular consumption of tea.

The NMCD rates green tea Likely Effective for genital warts and hyperlipidemia (abnormally high blood-lipid levels). [2]

This herb is rated Possibly Effective for:

• Cervical dysplasia
• Coronary artery disease (CAD)
• Endometrial cancer
• Hypertension (high blood pressure)
• Hypotension (low blood pressure)
• Oral leukoplakia (white patches in the mouth)
• Ovarian cancer
• Parkinson’s disease [2]

Some research studies have shown promising results using green tea for acne, breast cancer, cardiovascular disease, colds and flu, depression, esophageal cancer, infertility, leukemia, mental alertness, periodontal disease, and stress.

More human studies are still needed to determine the therapeutic efficacy of Camellia sinensis for these and other conditions. The FDA has not approved green tea extract as a drug to prevent or treat any medical conditions.

Blood Pressure

Green tea appears to have benefits for blood pressure regulation. It may help to normalize both high and low blood pressure.

NMCD rates Camellia sinensis as Possibly Effective for both hypotension (low blood pressure) and hypertension (high blood pressure). [2]

In a 2014 systematic review of randomized controlled trials, researchers from Griffith University in Australia concluded there was a significant benefit for people with high systolic pressure.

The authors of this study wrote that, “Green tea and its catechins may improve blood pressure, and the effect may be greater in those with systolic blood pressure ? 130 mm Hg.” [6]

More research in humans is needed to determine whether consumption of green tea can improve hypotension or hypertension in clinical settings.

If you are interested in taking this dietary supplement for cardiovascular health it is recommended that you speak with your doctor before beginning use.

Body Composition

Green tea supplements are commonly used for promoting weight loss, either on its own or in combination products. This product is purported to boost metabolism, increase resting energy expenditure and to suppress hunger cravings.

Some preliminary clinical evidence suggests that both caffeine and catechins may have thermogenic (heat-increasing) effects that could contribute to body weight and body fat reductions.

However, this evidence is limited, and further study is needed to confirm these effects. [2]

One 2014 study from Barcelona University in Spain evaluated both caffeine and catechin constituents from green tea for effects on body composition.

According to the authors of the study, “Green tea or green tea extracts […] exerts [sic] no statistically significant effect on the weight of overweight or obese adults. There is a small effect on the decrease in the percentage of fat mass, but it is not clinically relevant.” [7]

Further research trials are needed to understand how this supplement affects body fat or body weight and whether it can be used to support a weight reduction program.

Breast Cancer

In 2017, researchers in Iran reviewed evidence from in vitro (cultured cell) and in vivo (in live animals) studies on green tea’s possible protective effects against breast cancer.

It was found to have both chemopreventive and chemotherapeutic effects, meaning it may both prevent and treat breast cancer.

They concluded that Camellia sinensis blocked carcinogenesis (cancer development) and inhibited cellular proliferation (rapid replication of cells). [8]

According to the researchers, “The studies demonstrated anti-breast cancer activity of Camellia sinensis and its component by adjusting cell signaling pathways such as angiogenesis, apoptosis, and transcription factor.” [8]

The researchers state that drinking more green tea might reduce the risk of developing breast cancer. They say that the potential breast cancer chemopreventive effects of C. sinensis have been “highly confirmed” in both cell and animal studies. [8]

However, some clinical studies using green tea have shown low anticancer effects and others have shown no anticancer effects at all.

Most of the research has involved Asian women only. It is not clear if increasing tea consumption reduces breast cancer risk in other populations. [8]

Although some preliminary results have shown promising results, more clinical trials are needed to determine the therapeutic efficacy of green tea for any type of cancer.

The FDA has not approved this supplement as a drug for the prevention or treatment of cancer.

Camellia Sinensis Extract Supplements

The Natural Medicines Comprehensive Database reports that there are more than 7500 different dietary supplement products that contain Camellia sinensis.

Because there are so many different products to choose from, it is important to do your research and be selective, as some products available may be of substandard quality. [2]

Look for supplements that are certified by a third party to be organic, non-genetically modified, and free of adulterants or contaminants.

Green tea supplements are available in a few different forms including capsules, tablets, liquid drops, and bulk powder. Unless the processing method is described on a product, most extract products contain dried powdered tea leaves.

Many supplements are standardized to their total catechin content.

he NMCD states, “Green tea-containing beverages used in clinical research have been standardized to contain about 400 mg of total catechins per cup of green tea beverage or 302 mg of EGCG per cup.” [2]

Oral capsules are usually standardized to contain between 40-50% of catechins by weight. [2]

Camellia Sinensis Dosages

The NMCD reports the following adult oral doses of green tea have been used in clinical studies:

• 135 mg EGCG 3 times daily with meals for enhancing athletic performance
• Green tea extract with up to 2500 mg catechins daily for hyperlipidemia
• 4 cups of green tea with 928 mg catechins daily for 8 weeks for obesity
• 1.5 grams green tea extract daily for 12 months for colorectal cancer
• 1 cup of green tea 2 hours after meals for 4 weeks for hypertension
• 200 mg green tea catechins three times daily for 1 year for prostate cancer
• 3 or more cups of green daily for breast cancer
• 500-700 mg EGCG daily for amyloidosis [2]

One common dosage recommendation is 3 cups daily of a tea that provides between 240-480 mg of total polyphenols per cup. The tea generally consumed in between meals. [9]

If you are using an oral supplement, it is recommended to follow dosing directions provided on the package. If you are not sure about any of the directions, then ask a pharmacist or your doctor for clarification.

It is always best to discuss the best dose of Camellia sinensis for you with a medical professional who understands your health history.

Safety and Side Effects

The NMCD rates the safety of Camellia sinensis as follows:

• LIKELY SAFE when consumed as a beverage in moderate amounts
• POSSIBLY SAFE when used as an oral extract for up to 2 years
• POSSIBLY SAFE during pregnancy in moderate oral doses
• POSSIBLY SAFE during lactation in moderate oral amounts
• POSSIBLY SAFE in children when used in common dietary amounts
• POSSIBLY UNSAFE when used orally in large amounts during lactation
• POSSIBLY UNSAFE when used orally long-term or in high doses
• LIKELY UNSAFE when used orally in very-high doses (150-200 mg per kilogram) [2]

Camellia sinensis is generally well-tolerated in most people when consumed as a beverage in typical dietary amounts or as a supplement at recommended dosages.

Adverse side effects are rare. When they occur, they are generally gastrointestinal-based complaints like nausea, diarrhea, or abdominal discomfort. [2]

Rare side effects have been reported including hypertension, hypokalemia (low blood potassium levels), hypotension, irritation, muscle pain, nervous system stimulation, skin rashes, and thrombotic thrombocytopenic purpura (a rare blood disorder). [2]

Green tea contains 2-4% caffeine and large doses can cause caffeine-related side effects like hyperglycemia (low blood sugar), ketosis (elevated ketone bodies in the blood), massive catecholamine release and subsequent sinus tachycardia (elevated heart rate), and metabolic acidosis.

Caffeine in camellia sinensis extract might also cause anxiety, arrhythmia, chest pain, headache, hypokalemia, premature heartbeat, respiratory alkalosis, or ringing in the ears (tinnitus).

Drug Interactions

There are various prescription and over-the-counter medications that Camellia sinensis can interact with. Some of these include, but are not limited to:

• Blood thinners like aspirin and warfarin (Coumadin)
• Drugs that can cause liver damage like acetaminophen, isoniazid, and methotrexate
• Drugs used to treat migraine headaches or to prevent sleepiness
• Estrogen drugs including hormonal birth control pills and patches
• Statin drugs like atorvastatin and lovastatin
• Stimulants like amphetamine, Ephedra, and theophylline [2]

Be careful combining green tea supplements with other substances that contain caffeine to avoid overstimulation or other possible caffeine-related side effects.

This supplement can interfere with some laboratory tests including urine tests for catecholamines or calcium, and chemical stress tests that use dipyridamole/adenosine. You should stop consuming green tea at least 24 hours before any lab tests.

Because of possible effects on heart rate, blood pressure, and other factors, you should discontinue using this product at least 2 weeks prior to any surgery.

Interactions with other drugs, herbs, and supplements exist. It is recommended that you speak with your doctor before beginning to use Camellia sinensis supplements to determine whether they are appropriate for you.

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