White tea

White Tea (Camellia sinensis)

1. Identity: Botanical Name, Natural Source, and Common Forms

Botanical and Chemical Identity

White tea is produced from the fresh leaves and buds of Camellia sinensis and C. sinensis var. assamica. The plant belongs to the family Theaceae. White tea is one of China's six official tea categories — alongside yellow, green, oolong, black, and pu-erh — and is the category with the least processing of any of the six.

True white tea comes from a few select cultivars of the tea plant — specifically the Da Bai and the Da Hao tea plants from Fuding County in Fujian Province, China. These two types of tea plants are very similar and contain several small and downy white hairs on the buds and leaves of the plant. The name "white tea" does not describe the colour of the brewed liquor (which is pale golden to peach) but the white down visible on the unprocessed buds of the tea plant.

The plant Camellia sinensis is the source of different teas — white, green, yellow, oolong, black, and pu-erh — consumed worldwide, and they are classified by the oxidation degree of their bioactive compounds. White tea undergoes the least oxidation of all true teas. There is no rolling, kill-green steaming, pan-firing, or shaping. The complete absence of kill-green processing means Silver Needle undergoes a slow, natural, minimal oxidation during withering — not enough to classify it as green tea or oolong, but enough to develop the subtle complexity of flavour that distinguishes white tea from the purely fresh character of green tea.

Processing and Production

Silver Needle is made up of only buds hand-plucked from the tea bush. The freshly harvested white tea buds are fanned out into a single layer on bamboo trays and air-dried naturally until 85–90% of their moisture is removed. After 36 to 38 hours of withering, the drying process is then completed with a gentle baking to stabilize the tea. The very low temperature drying is designed to preserve the white color of the buds. The technique of white tea production is not very old; not until somewhere between 1772 and 1782 was true white tea produced. The process was developed by the Xiao family in Jiang Yang County in northern Fujian and the technique quickly spread to Fuding, Zheng He, and Song Xi.

Common Commercial Grades and Forms

White tea is commercially available in several distinct grades and preparations:

• Bai Hao Yinzhen (Silver Needle / 白毫銀針): A white tea chiefly produced in Fujian Province in China. It is more commonly known just as Yinzhen. Amongst white teas this is the most expensive variety and the most prized as only top buds are used to produce the tea.
• Bai Mudan (White Peony): Made from the bud and the first two leaves of the shoot, representing a less costly but still high-quality grade from Fujian Province.
• Gongmei and Shoumei: Lower grades made from larger, more open leaves harvested later in the season.
• Supplement and extract forms: Innovative applications range from ready-to-drink infusions to skincare products. White tea has been proposed as a raw material for supplements, meal replacements, and confectionery.

By the traditional definition, true white tea can only be made from the Da Bai Hao bushes. While the leaves from the Da Bai Hao bush can be processed to make both green and white tea, no other tea bush leaves can be used to make true white tea.

2. Traditional and Historical Use

Early Historical Records

Tea culture emerged in the Tang dynasty, and flourished in the succeeding eras as a major cultural practice and as a major export good. The earliest references to a pale, minimally processed tea appear in Chinese imperial records. The first mention of White Tea appeared in the "Treatise on Tea," written by Emperor Huizong (1107–1110). The emperor was a well-known tea connoisseur, while white tea was his tea of choice. His book included profoundly detailed descriptions, as well as rules for the making and evaluation of tea.

In the treatise, it is mentioned that Emperor Huizong particularly enjoyed drinking 'Bai Cha' (Bai means white, Cha means tea), which was, in fact, an unprocessed, pale, green tea. This is the first historical record of an unprocessed tea that had a white tea-like appearance.

During the Song Dynasty (960–1279), white tea became the tea of choice for the royal court and was always given as a tribute to the emperor. The tea cakes were ground into a very fine powder and then whisked in boiling water to produce a frothy liquid (similarly to matcha).

The Modern White Tea Tradition

The white tea known today was first commercially produced from the very first white tea plant varieties discovered in China's Fujian Province in the 1700s. Subsequently, a loose leaf version of white tea was developed from these plants, known for producing large and beautiful tea buds. Today these bush varieties are still used to produce white tea. Only in the late 1800s did Silver Needle become popular and begin to be exported out of China, followed by White Peony in the early 1900s.

Traditional Medicinal Use

Like green and yellow tea, white tea is considered cooling in Chinese Medicine. Silver Needle in particular is considered a very effective cooling tea and used to treat inflammation, dental problems, fevers, and skin problems.

Even in contemporary times, individuals residing in Southern China and other Southeast Asian nations continue to frequently utilize white tea for alleviating inflammatory responses, such as sore throat and oral ulcers.

In early tea-drinking cultures, such as during the Shang Dynasty of China (1766 BC – 1050 BC), tea leaves were air dried and then typically added to a boiling pot full of water and herbs and spices in order to create a blend used for medicinal purposes. It is important to note, however, that attributing these early uses specifically to "white tea" as a defined category is anachronistic; the formal category of white tea as understood today did not exist until the 18th century.

3. Key Constituents and Active Compounds

Polyphenols and Catechins

The nutritional value and healthful properties of tea are closely related to the large amounts of three major characteristic constituents including polyphenols (mainly catechins), theanine, and caffeine.

Polyphenol concentrations in white tea range from 10.60 to 25.95 g per 100 g, while in green tea they range from 13.7 to 24.7 g per 100 g. White and green teas had the highest concentrations of catechins, with EGCG accounting for approximately 59%, EGC (19%), ECG (13%), and EC (6%).

Tea polyphenols, commonly known as catechins, are flavonoid compounds with a basic structure of α-phenyl-benzopyran, which are about 18% to 36% of the dry weight of tea leaves. The most important types of tea polyphenols are (−)-epigallocatechin-3-gallate (EGCG), (−)-epicatechin-3-gallate (ECG), (−)-epigallocatechin (EGC), and (−)-epicatechin (EC).

Epigallocatechin-3-gallate (EGCG), a flavon-3-ol polyphenolic compound, is the most active and abundant natural catechin found in tea, representing 50–80% of the total catechin content, followed by (−)-epigallocatechin (EGC), (−)-epicatechin gallate (ECG), (−)-epicatechin (EC), and (+)-catechin (C).

White tea has been proven to have a maximum level of polyphenols that is even higher than that in green tea, especially catechins and their derivatives. It should be noted, however, that this finding is variable across studies and depends heavily on grade, harvest season, and brewing method.

Methylxanthines: Caffeine and Theophylline

The sensory and functional properties of teas are affected by the amount of methylxanthines (caffeine and theobromine), amino acids (L-theanine), and reducing sugars in their composition.

Caffeine levels were highest in black and yellow tea (14 ± 1.0 mg/200 mL and 13.8 ± 0.2 mg/200 mL, respectively), both of which were significantly higher than the levels in green, white, and oolong tea (11 ± 2.1 mg/200 mL; 5.8 ± 0.7 mg/200 mL; and 4 ± 1.6 mg/200 mL, respectively). These per-cup values reflect conditions of standardized brewing; caffeine content in a finished cup varies widely depending on leaf grade, steeping time, and water temperature.

White tea contains theophylline and caffeine. Theophylline has been demonstrated to induce acid reflux, a factor which can precipitate the development of erosive oesophagitis.

L-Theanine

Theanine, one of the most abundant amino acids found in tea, has received considerable attention in recent years. The mean L-theanine content of white, green, oolong, and black teas were 6.26, 6.56, 6.09, and 5.13 mg/g, respectively. Based on available scientific data, it can be stated that samples with lower caffeine/theanine ratio have less pronounced stimulating effect.

Other Bioactive Constituents

Chemical investigation of plants in the Camellia section Thea has led to the identification of 398 compounds, including hydrolyzable tannins, flavan-3-ols, flavonoids, terpenoids, alkaloids, and other phenolic and related compounds.

The chemical composition of the flower, from which white tea originates, consists of 34% carbohydrates (glucose, fructose, sucrose, and polysaccharides), 12% phenolic compounds, 28% crude proteins and 3% saponins. Additionally, it contains a wide variety of amino acids, such as aspartic acid, serine, histidine, arginine, γ-aminobutyric acid, threonine, tyrosine, valine, methionine, leucine, phenylalanine, lysine, and theanine.

White tea stands out as a rich source of polyphenols, polysaccharides, and saponins. The quercetin-class flavonols are also present. Quercetin is a flavonoid found in various foods and plants, including green tea.

4. Mechanisms of Action

Antioxidant Activity

Tea catechins present antioxidant activity by scavenging free radicals, chelating redox-active transition-metal ions, inhibiting redox-active transcription factors, inhibiting pro-oxidant enzymes, and inducing antioxidant enzymes.

Iron also catalyzes oxidation; however, the catechol structure in tea polyphenols can chelate Fe²⁺. Different catechin compounds have different inhibitory effects on lipid peroxidation, and the inhibitory effects are in the order EGCG > ECG > EGC > EC.

Owing to the presence of multiple hydroxylic groups in their chemical structure, polyphenols can reduce and quench reactive oxygen species (ROS) and chelate metal ions. Tea polyphenols can also stimulate endogenous antioxidant defenses through the activation of the nuclear factor erythroid 2-related factor (Nrf2) pathway and regulate pro-inflammatory and anti-inflammatory signaling and factors such as NF-κB, TNF-α, Toll-like receptors, and COX-2.

Antimicrobial Mechanisms

Tea has antimicrobial properties due to the polyphenols it contains. The antimicrobial activity of unfermented tea is higher than that of fermented or semi-fermented tea. High antimicrobial activity is found in teas that have high total polyphenol concentrations and antioxidant activity. EGCG and EGC are the major components responsible for antimicrobial activity. It has been reported that EGCG and EGC inactivate the retrovirus that disrupts the human immune system by inhibiting the transcriptase enzyme which allows the virus to form in host cells.

Anti-inflammatory Mechanisms

Catechins, the major polyphenolic compounds in green tea, exert vascular protective effects through multiple mechanisms, including antioxidative, anti-hypertensive, anti-inflammatory, anti-proliferative, anti-thrombogenic, and lipid-lowering effects.

Metabolic and Lipid-Modulating Mechanisms

Polyphenols stimulate nutrient absorption by inhibiting the enzyme pancreatic lipase (PL), which is effective in lipid metabolism. The outcome is a decrease in blood glucose and lipid profile. While fat oxidation and energy expenditure increase, body weight decreases. In addition, tea catechins lower glucose concentrations.

Tea extracts may exert their anti-obesity effects by stimulating thermogenesis in brown adipose tissue through the interaction between catechin polyphenols and norepinephrine, which improves body weight and body fat levels.

Bioavailability of Key Catechins

The mechanism for catechins being transported across the epithelium is principally based on passive diffusion, including paracellular and transcellular diffusions. Cell studies have also suggested that EGCG underwent active efflux after absorption by ATP-dependent proteins.

After repeated oral dosing, plasma C_max values of free EGCG were reported to be between 0.3 and 0.63 µM, and the mean AUC_0–24h of 2.0–5.8 µM × h following 800 mg EGCG/day from Polyphenon E taken with a meal for 4 weeks. These figures are derived from isolated EGCG supplementation studies, not from whole white tea beverage consumption.

5. Scientific Evidence by Health Area

5.1 Antioxidant Properties

Despite some studies reporting that green tea is a richer polyphenol source than white tea, it is known that the strongest antioxidant activity sequence is white, green, and black tea. In one study, antioxidant and antimicrobial properties of black, green, and white tea were examined and the total phenolic substance was detected highest in white tea.

Total phenolics (125.9–295.4 mg gallic acid equivalents/g dried extract) and total flavonoids (35.2–69.7 mg rutin equivalents/g dried extract) were higher in green teas than in white teas and flowers in Azorean Camellia sinensis varieties. This illustrates that comparisons of white versus green tea antioxidant activity remain inconsistent across studies and are highly dependent on cultivar, harvest conditions, and extraction method.

Evidence strength: The antioxidant superiority of white tea relative to other teas is supported by multiple in vitro assays but results are mixed across studies. No large-scale controlled human trials have specifically confirmed that consuming white tea raises human plasma antioxidant capacity more than equivalent amounts of green tea.

5.2 Antimicrobial Activity

Recent research has illuminated the specific antimicrobial potential of white tea against common pathogens. Its inhibitory effects on the growth of bacteria like Staphylococcus aureus and Streptococcus mutans, as well as fungi such as Candida albicans, highlight its broad-spectrum efficacy. The versatility of white tea in combating both Gram-positive and Gram-negative bacteria underscores its potential as a natural antimicrobial agent.

White tea's efficacy has been substantiated through in vitro studies, demonstrating antioxidant and anti-inflammatory activity in primary human skin fibroblasts, as well as antibacterial activity and anti-adherence and anti-protease effects.

Evidence strength: Antimicrobial activity is established in in vitro and laboratory settings. Clinical (human) evidence specifically for white tea as an antimicrobial agent is lacking. Findings should not be extrapolated to in vivo therapeutic applications without further clinical investigation.

5.3 Obesity, Metabolic Health, and Body Composition

One of the most clinically studied areas for white tea is its potential effect on body weight and metabolic parameters. A key human clinical study specifically investigated white tea in obese patients:

Patients between the ages of 18 and 65 and with a body mass index of 30 and above (kg/m²) were included in this study. Patients who met the exclusion and inclusion criteria based on anthropometric and biochemical measurements were randomly assigned into 4 groups: control, orlistat, metformin, and white tea groups. Pancreatic lipase (PL) decreased significantly in the white tea group. Although it fell in other groups too, it was not significant. In an in vitro study investigating PL activity, white tea inhibited PL activity more than green tea.

White tea plays an important role in the regulation of lipid metabolism. Despite a lack of clinical studies, animal studies have confirmed the health benefits of white tea. Rats treated with white tea extract showed an effective decrease in lipid-related parameters. White tea extract significantly decreased total cholesterol and low-density lipoprotein-cholesterol (LDL-c).

In addition to animal tests, in vitro studies have been conducted to identify the hypolipidemic effects of white tea. Researchers found strong lipolytic and antiadipogenic effects of white tea extract on human subcutaneous preadipocytes.

Animal studies have further investigated white tea against high-fat-diet (HFD)-induced obesity. One study aimed to evaluate the effects of white tea on metabolic parameters (HOMA-IR, BMP4, Gremlin1) and GREM1 expression in rats made obese by a high-fat diet. A total of 40 male Sprague-Dawley rats were randomized into five groups: a standard diet group; a high-fat diet group; an HFD + orlistat group; an HFD + 50 mg/kg white tea group; and an HFD + 150 mg/kg white tea group. Obesity was induced by feeding the rats a 45% high-fat diet for 3 weeks. White tea supplementation significantly reduced weight gain and HOMA-IR compared to the HFD group. Given the short intervention duration and the exploratory design of this animal study, the findings should be interpreted with caution.

Evidence strength: Preliminary. There is one small human clinical study and a larger body of animal and in vitro evidence. Despite a lack of clinical studies, animal studies have confirmed the health benefits of white tea in this domain. Large-scale, well-controlled, randomized human trials are absent.

5.4 Cardiovascular Health

Epidemiological, clinical, and experimental studies have established a positive correlation between green tea consumption and cardiovascular health. Catechins, the major polyphenolic compounds in green tea, exert vascular protective effects through multiple mechanisms, including antioxidative, anti-hypertensive, anti-inflammatory, anti-proliferative, anti-thrombogenic, and lipid-lowering effects. Because white tea shares these catechins — primarily EGCG, EGC, ECG, and EC — much of the cardiovascular evidence for the catechin class applies mechanistically to white tea.

Overall, the observational data suggest a benefit for tea in cardiovascular contexts, but results are mixed and likely confounded by lifestyle and background dietary factors. The weight of evidence indicates favorable effects on risk factors and a number of plausible mechanisms have been elucidated in experimental and translational human studies.

Evidence strength: Mechanistic plausibility is strong based on shared catechin chemistry. Direct human clinical evidence specifically for white tea in cardiovascular endpoints is limited; most of the relevant clinical trial evidence involves green tea or isolated catechin (EGCG) preparations.

5.5 Cancer Biology (Chemopreventive Research)

Among the major tea polyphenols, EGCG showed the most potent antiproliferative effects and significantly induced cell cycle arrest in the G1 phase and cell apoptosis in human colorectal cancer cell lines.

In a 1-year carcinogenicity bioassay in rats, animals were treated with three short cycles of 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP)/high-fat diet, followed by 2% white tea (wt/vol), 0.05% EGCG, or 0.065% caffeine as the sole source of fluid intake. Thirty-two percent of the PhIP/HF controls survived to 1 year, compared with 50%, 48.7%, and 18.2% in groups given white tea, EGCG, and caffeine, respectively. For all sites combined (excluding the colon), tumor incidence data were: PhIP/HF 69.5%, PhIP/HF + EGCG 48.7%, PhIP/HF + white tea 46.9%, and PhIP/HF + caffeine 13.3%. Unexpectedly, a higher incidence of colon tumors was detected in rats post-treated with white tea (69%) and caffeine (73%) compared with the 42% incidence in PhIP/HF controls.

It is important to note that a substantial literature exists on tea and coffee consumption in humans, which does not indicate an adverse effect on tumor outcome — indeed, some studies suggest a protective role for these caffeinated beverages.

Recent investigations have associated white teas with anti-carcinogenic, immune-boosting, and antioxidative properties that may impact human health in a manner comparable to green teas.

Evidence strength: The chemopreventive evidence for white tea is largely preclinical (in vitro cell-line studies and rodent carcinogenicity bioassays). The human clinical evidence is indirect, based on epidemiological data for tea consumption generally and EGCG clinical trials, not white tea specifically. The rodent study above also illustrates the complexity and context-dependency of outcomes. No human clinical trials have directly assessed white tea as a chemopreventive agent.

5.6 Neuroprotection

White tea's neuroprotective and anti-amyloid β effects have been substantiated through in vitro studies. Research has shown that tea polyphenols, including those found in white tea, may have relevance to neurodegenerative disease pathways. EGCG has attracted significant research interest due to its beneficial health effects including antioxidation, anti-diabetes, anti-inflammation, and anti-tumorigenesis activity.

White tea extract has been shown to have a significant effect on the oxidative stress injury of lung fibrosis induced by nano-sized SiO₂ in rats. A white tea extract treatment group and an EGCG group showed significant alleviation in the content of nitrogen monoxide (NO), inflammatory factor interleukin-6 (IL-6), and glutathione peroxidase (GSH-Px) activity in the lungs of the rats.

Evidence strength: Preliminary; largely confined to in vitro and animal models. Human clinical trials specifically examining white tea for neuroprotective endpoints do not exist as of current literature.

5.7 Skin Health and Dermatology

White tea has demonstrated antioxidant and anti-inflammatory activity in primary human skin fibroblasts. Polyphenols are usually recognized to be responsible for the remarkable antioxidant properties of green tea, which led to an interest in its health benefits as a nutraceutical and preventive strategy for cardiovascular, metabolic, inflammatory, and degenerative diseases.

Particular attention has been paid to the antioxidant, anti-hyaluronidase, anti-inflammatory, slimming, hair-strengthening, photoprotective, and sealing blood vessel properties of tea extracts in cosmetic applications.

Various studies suggest white tea's potential in enhancing gut health, supporting endurance, and contributing to photoprotection in skincare.

Evidence strength: In vitro and mechanistic evidence supports antioxidant and anti-inflammatory activity in skin cells. Systematic clinical trials specifically examining white tea for skin health endpoints in humans are limited; most clinical evidence in this space involves green tea extracts and EGCG.

5.8 Oral / Dental Health

An in vitro laboratory study used white tea extract in calcium silicate cement formulations. This in vitro research used forty removed human molar teeth. After the teeth were sectioned to obtain dentin specimens, the dentin was randomly divided into four groups according to the type of treatment: control; conventional calcium silicate cement; calcium silicate cement combined with 5% white tea extract; and calcium silicate cement combined with 10% white tea extract. The findings underscore the potential of white tea extract as a beneficial additive in dental materials, particularly in enhancing the mechanical properties of calcium silicate cement. The significant improvement in flexural strength observed in the extract-treated groups may be attributed to the synergistic interaction between the bioactive compounds in white tea and the calcium silicate matrix.

Strong antioxidant and anti-inflammatory characteristics of white tea extract, which is high in polyphenols and flavonoids, may shield dentin collagen from enzymatic degradation. Antioxidants have been shown in earlier research to suppress matrix metalloproteinases (MMPs) that break down collagen, protecting dentin's structural integrity.

Evidence strength: Preliminary, based on a single in vitro study using extracted human teeth. No clinical (patient) trials have assessed white tea for dental endpoints.

5.9 Radioprotection (Emerging Research)

A study assessed the radiation protection or repair effect of one-year (WT-1Y) and seven-year (WT-7Y) stored white teas. HGC-27 cells exposed to ¹³⁷Cs γ-rays (30 Gy) exhibited significant changes in cell structure, apoptosis, ROS, LDH, and expression of p53 and Caspase-3. The results showed that WT-1Y and WT-7Y acted as antioxidants, showing reduced ROS and LDH levels, and had increased CAT and SOD activities as well as cell survival rate.

A Spearman analysis of the differential metabolites in WT-1Y and WT-7Y with cellular radioprotective indicators revealed that metabolites such as EGC, procyanidin B4, and phenolic acids (abundant in WT-1Y), quercetin-3-glucosylrutinoside, and caffeine (enriched in WT-7Y) contributed to their distinct effects.

Evidence strength: Very preliminary; entirely in vitro (cell line). No human data exist.

6. Body Systems and Health Areas of Association

Based on the available literature, white tea has been studied or proposed for relevance to the following body systems:

• Metabolic system: Lipid metabolism, glucose regulation, body weight, pancreatic lipase inhibition, insulin sensitivity (mostly animal and in vitro evidence; one small human study).
• Cardiovascular system: Blood pressure, endothelial function, lipid profiles — based primarily on shared catechin chemistry with green tea and indirect human data.
• Immune and inflammatory system: Anti-inflammatory effects via NF-κB, TNF-α, COX-2 inhibition (in vitro and animal data).
• Integumentary system (skin): Antioxidant and anti-inflammatory activity in skin fibroblasts; photoprotection; cosmetic applications.
• Nervous system: Neuroprotective and anti-amyloid-β effects (in vitro only).
• Oral/dental health: Antibacterial activity against oral pathogens; potential dentin-protective effects in dental materials (in vitro).
• Gastrointestinal system: Enzyme inhibition (lipase, amylase); emerging gut microbiome research.
• Oncology (preclinical): Antiproliferative, apoptotic, and antimutagenic effects in cell and animal models.

Benefits associated with white tea bioactive components include antioxidant, anti-inflammatory, anti-aging, anti-radiation, anti-hyperglycemia, anti-hyperlipidemia, neuroprotection, and cardiovascular-protection properties. It must be emphasized that the majority of these associations are based on preclinical evidence and that the clinical translation of these properties in humans remains an area requiring substantially more research.

7. Dosage Forms and Dosages Reported in Studies

There is no standardized recommended dosage for white tea as a dietary supplement. The following dosages have been reported in published research:

• Beverage (infusion): A typical tea, prepared by 1 g dried leaf in 100 mL of water for 3 minutes, contains 250–350 mg of tea solid materials, of which 30–42% is catechin and 3–6% is caffeine.
• Animal study (metabolic/obesity): In a rat HFD-obesity model, groups received HFD + 50 mg/kg white tea or HFD + 150 mg/kg white tea.
• EGCG supplementation (from Polyphenon E, not white tea specifically): 800 mg EGCG/day from Polyphenon E taken with a meal for 4 weeks was used in a clinical pharmacokinetic study.
• In vitro dental study: Calcium silicate cement combined with 5% or 10% white tea extract concentrations were evaluated.
• Carcinogenicity bioassay: 2% white tea (wt/vol) was administered as the sole source of fluid intake in a 1-year rat study.

No government body (NIH, EFSA, WHO) or recognized pharmacopeia has established an official recommended daily intake for white tea or its standardized extract as a dietary supplement.

8. Safety Considerations and Drug Interactions

General Safety Profile

White tea consumed as a beverage is considered generally safe in typical dietary amounts. Its safety considerations are closely aligned with those of green tea, sharing the same plant source and similar active compounds. Side effects of green tea extract supplements include nausea, constipation, abdominal discomfort, and increased blood pressure. Although uncommon, liver injury has been reported in some people who used green tea products, primarily green tea extracts in tablet or capsule form.

Individuals with a specific variant of a gene that plays an important role in immune function appear to be especially susceptible. Between 5 and 15 percent of Americans have this variant.

Caffeine-Related Adverse Effects

The presence of caffeine in white tea has been demonstrated to induce adverse effects, including symptoms such as nausea and vomiting. Caffeine-related side effects can range from mild to serious and include headache, nervousness, sleep problems, vomiting, diarrhea, irritability, irregular heartbeat, tremor, heartburn, dizziness, ringing in the ears, convulsions, and confusion.

Theophylline-Related Adverse Effects

White tea contains theophylline and caffeine. Theophylline has been demonstrated to induce acid reflux, a factor which can precipitate the development of erosive oesophagitis. The burning sensation experienced may be attributable to elevated levels of theophylline entering the body.

High-Dose Catechin Effects

Catechins, a type of polyphenol found in white tea, have been shown to possess therapeutic benefits in treating various diseases. However, in excessive doses, they have the potential to cause excessive pro-oxidant effects, triggering inflammatory reactions, necrosis, and steatosis in the liver.

Iron and Folate Absorption

The high polyphenol content of white tea has been demonstrated to have a potential inhibitory effect on iron absorption, which may consequently result in iron deficiency and the subsequent development of anaemia.

Studies have shown that green tea consumption can lead to nutrient–nutrient interactions. The majority of studies indicate that the bioavailability of folic acid and iron has declined. It is recommended to reduce tea consumption during pregnancy and never drink tea near meals.

Drug Interactions

Green tea at high doses has been shown to reduce blood levels and therefore the effectiveness of the drug nadolol, a beta-blocker used for high blood pressure and heart problems. Green tea extract can reduce blood levels of the cholesterol-lowering drug atorvastatin. A study funded by the National Center for Complementary and Integrative Health showed an interaction between green tea and the drug raloxifene, which is used to treat osteoporosis.

The importance of subject genotyping for enzymes involved in catechin metabolism should be noted to aid in interpreting liver injury biomarkers, and the necessity of assessing drug–catechin interactions in clinical contexts has been underscored in the literature.

Pregnancy and Lactation

A cross-sectional study of about 400 pregnant women evaluated the association between tea consumption during pregnancy and the risk of iron deficiency anemia. Serum iron and ferritin levels were higher in non-tea drinkers, whereas total iron-binding capacity was higher in tea drinkers. Women who drank tea during pregnancy developed anemia. Caffeine passes into breast milk and can affect a nursing infant. Caffeine intake should be kept low (2–3 cups per day) while breast-feeding. High intake of caffeine while breast-feeding can cause sleep problems, irritability, and increased bowel activity in breast-fed infants.

Preclinical Oncological Caution

A note of scientific caution comes from a rodent carcinogenicity study. A higher incidence of colon tumors was detected in rats post-treated with white tea (69%) and caffeine (73%) compared with the 42% incidence in PhIP/HF controls. White tea and caffeine increased colon tumor volume in the rat. Importantly, a substantial literature on tea and coffee consumption in humans does not indicate an adverse effect on tumor outcome; indeed, some studies suggest a protective role for these caffeinated beverages. This rodent finding has not been replicated in humans and should be interpreted in the context of the specific carcinogen-treatment model used.

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