Diet and nutritionCoffee and green tea — allies of health or silent enemies?
Sources: 10 · Article: 17 230 characters
Henryk Różański presents green tea as a possible aid to health, but warns against strong, long-steeped tea and promises of miraculous effects.
- He attributes to it, among other things, anti-inflammatory, diuretic, and stimulating effects, as well as effects on blood glucose and cholesterol levels.
- On the other hand, strong tea may interfere with digestion and the absorption of medicines, and drinking green tea on an empty stomach may cause nausea, cramps, or vomiting.
What the authors write
Henryk Różański
Green tea polyphenols are said to protect cells, reduce inflammation, and inhibit processes that contribute to cancer.
„It has antioxidant and free-radical-scavenging effects, stabilizes the structure of basic membranes (biomembranes), and blocks the release of inflammatory mediators and allergic reactions. It inhibits the harmful effects of nitrosamines on cells (an inhibitor of N-nitrosation). It protects cells from the harmful effects of asbestos (macrophages, red blood cells).”Działa antyoksydacyjnie i przeciwrodnikowo, stabilizuje strukturę błon elementarnych (biomembran), blokuje uwalnianie mediatorów stanu zapalnego i reakcje alergiczne. Hamuje szkodliwy wpływ nitrozoamin na komórki (inhibitor N-nitrozacji). Chroni komórki przed szkodliwym wpływem azbestu (makrofagi, erytrocyty).
Henryk Różański
Green tea is said to lower blood glucose, cholesterol, and lipid levels.
„It is also worth adding that green tea lowers blood glucose, cholesterol, and lipid levels. However, the tea leaves should be fresh, dried quickly, and well packaged, and we should pay attention to how the preparation is made, depending on the intended use.”Warto również dodać, że zielona herbata obniża stężenie glukozy, cholesterolu i lipidów we krwi. Ważne jest jednak, aby liście herbaty były świeże, szybko wysuszone, dobrze zapakowane i zwracajmy uwagę na sposób przyrządzenia preparatu zależnie od potrzeby.
Henryk Różański
Tea is said to be stimulating, increase urine production, and support the treatment of certain inflammatory conditions and infections of the digestive tract.
„It has analeptic and psychostimulant effects, meaning that it stimulates the cerebral cortex, heart, and skeletal muscles. It increases diuresis (has a diuretic effect). It stimulates metabolism. It increases peristalsis in the digestive tract. It stimulates pulmonary breathing. It reduces inflammation of the mucous membranes and skin, which is why it works well as a compress on the eyes for inflammation of the eyelids and conjunctiva.”Działa analeptycznie i psychostymulująco, czyli pobudzająco na korę mózgową serce i mięśnie szkieletowe. Zwiększa diurezę (wpływ moczopędny). Pobudza przemianę materii. Zwiększa ruchy robaczkowe przewodu pokarmowego. Pobudza oddychanie płucne. Hamuje stany zapalne błon śluzowych i skóry, dlatego sprawdza się w okładach na oczy przy zapaleniu powiek oraz spojówek.
Henryk Różański
Green tea on an empty stomach may cause nausea, stomach and intestinal cramps, and even vomiting in some people.
„It worsens gastroesophageal reflux, increases the acidity of gastric juice, and stimulates intestinal peristalsis. As a result, many people experience nausea, stomach and intestinal cramps, and even vomiting after drinking green tea on an empty stomach. It affects the blood and bone marrow by lowering the number of T lymphocytes and increasing the activity and number of suppressor lymphocytes.”Wzmaga reflux żołądkowo-przełykowy i zwiększa kwasowość soku żołądkowego i pobudza perystaltykę jelit, dlatego u wielu osób po wypiciu herbaty zielonej na czczo występują objawy nudności, skurcze żołądka i jelit, a nawet wymioty. Wpływa na krew i szpik kostny obniżając liczbę limfocytów T, a podnosząc aktywność i liczbę limfocytów supresorowych.
Henryk Różański
Strong, long-steeped tea contains a lot of tannins, which may inhibit digestion.
„It should also be remembered that strong tea, especially tea steeped for a long time or boiled, is rich in tannins, which also inhibit digestion in our digestive tract by denaturing the protein structure of enzymes. In animal husbandry, tannins are even considered antinutritional factors because they precipitate gastric, pancreatic, and intestinal enzymes.”Pamiętać należy również, że mocna herbata, szczególnie długo parzona, gotowana jest bogata w garbniki, które również hamują trawienie w naszym przewodzie pokarmowym poprzez denaturację struktury białkowej enzymów. W zootechnice nawet garbniki są uważane za czynniki antyżywieniowe właśnie poprzez strącanie enzymów żołądkowych, trzustkowych, czy jelitowych.
Henryk Różański
Do not take certain medicines with strong tea or combine it with iron, zinc, or calcium supplements, vitamin B12, or folic acid, because it may interfere with their absorption.
„Strong tea should not be used to take medicines, especially those with a peptide/polypeptide structure (e.g. some antibiotics and enzyme preparations), an amide structure, or an imidazole structure. It is incompatible with iron, zinc, and calcium preparations (e.g. calcium gluconate), vitamin B12, and folic acid (this involves chelation reactions, which in this case impair the absorption of the medicine).”Mocna herbata nie powinna być stosowana do popijania leków, szczególnie o budowie peptydowej/polipeptydowej (np. niektóre antybiotyki, preparaty enzymatyczne), amidowej, imidazolowej; wykazuje niezgodność z preparatami żelaza, cynku, wapnia (np. glukonianem wapnia), witaminą B12, kwasem foliowym (chodzi o reakcje chelatowania – upośledzające w tym przypadku wchłanianie leku).
Henryk Różański
The effects of tea depend on how it is prepared: briefly steeped tea is more stimulating, while longer steeping increases the tannin content.
„A short-steeped, 3-minute infusion contains more xanthine alkaloids than tannins, so it has a stronger stimulating effect than an astringent one. A long-steeped infusion — over 10 minutes — contains more tannins. Tannins impair the absorption of xanthine alkaloids and tan the mucous membrane of the digestive tract, further hindering the absorption of other psychoactive substances.”Napar krótkotrwały, 3-minutowy wykazuje większą zawartość alkaloidów ksantynowych niż garbników dlatego działa silniej pobudzająco niż ściągająco. Napar długotrwały – ponad 10 minutowy zawiera więcej garbników. Garbniki upośledzają wchłanianie alkaloidów ksantynowych, garbują błonę śluzową przewodu pokarmowego, utrudniając dodatkowo absorpcję innych substancji psychoaktywnych.
Henryk Różański
Henryk Różański warns against treating green tea as something that prevents almost every disease.
„Manufacturers of green tea-based products promise “miracles,” as if tea were a cure-all for every human ailment and prevented almost every disease. As for cosmetics, products based on tea extracts should, of course, stop the skin from aging and keep us young and beautiful until we die.”Producenci preparatów opartych na herbacie zielonej obiecują “cuda na kiju” jakoby herbata była panaceum na wszystkie dolegliwości ludzi i zapobiegała prawie wszystkim chorobom. Jeżeli chodzi o kosmetologię to oczywiście preparaty oparte na wyciągach z herbaty powinny zatrzymać starzenie się skóry i zachować nas młodych i pięknych aż do śmierci.
Henryk Różański
Henryk Różański points out that examples of countries with high tea consumption do not prove that drinking tea alone ensures a longer life.
„Life expectancy, for example: Ireland consumes more than 3 kg of tea per person per year, but ranks 32nd among the countries of the world for life expectancy. The same is true of Mauritania: 3.22 kg of tea per person, but 157th in the world for life expectancy. The United Arab Emirates consumes 6.24 kg of tea per person; life expectancy is 75.69 years, placing it 49th in the world (see http://www.wprost.pl/ar/318921/Herbata-kto-ja-pije-a-kto-produkuje/ and http://pl.wikipedia.org/wiki/Lista_pa%C5%84stw_%C5%9Bwiata_wed%C5%82ug_oczekiwanej_d%C5%82ugo%C5%9Bci_%C5%BCycia). They are therefore far behind the Swiss, who rank 6th in the world for life expectancy, while tea consumption in Switzerland is 0.22 kg per person per year (85th in the world).”5 długości życia, dla przykładu: Irlandia – ilość spożycia herbaty na mieszkańca w ciągu roku wynosi przeszło 3 kg, ale długość życia wśród krajów świata plasuje się na 32 miejscu; podobnie jest z Mauretanią – 3,22 kg herbaty na mieszkańca, ale pod względem długości życia 157 miejsce na świecie; Zjednoczone Emiraty Arabskie – zużycie herbaty na mieszkańca 6,24 kg, długość życia mieszkańca 75,69 lat co daje 49 miejsce w świecie (patrz http://www.wprost.pl/ar/318921/Herbata-kto-ja-pije-a-kto-produkuje/ oraz http://pl.wikipedia.org/wiki/Lista_pa%C5%84stw_%C5%9Bwiata_wed%C5%82ug_oczekiwanej_d%C5%82ugo%C5%9Bci_%C5%BCycia) daleko więc im do Szwajcarów, którzy mają 6 miejsce pod względem długości życia w świecie, przy czym zużycie herbaty na Szwajcara wynosi 0,22 kg/rocznie (85 miejsce w świecie).
Henryk Różański
The average caffeine content of green tea is 2.2%.
„Black and green tea differ in their polyphenol and aromatic substance content. The methylxanthine content of green tea is slightly lower; the average caffeine (theine) content is 2.2%. Theobromine, theophylline, and dimethylxanthine also have significant effects (diuretic, bronchodilating, and psychomotor-stimulating).”Herbata czarna i zielona różnią się pod względem zawartości polifenoli i substancji aromatycznych. Zawartość metyloksantyn w herbacie zielonej jest nieco niższa, średnia zwartość kofeiny (teiny) wynosi 2,2%. Dużą aktywność (moczopędną, rozszerzającą oskrzela, pobudzającą psychoruchowo) wykazują również teobromina, teofilina i dimetyloksantyna.
Michał Tombak
In the ORAC values table, green tea scores 1772 per 100 g of product.
„Nuts: walnuts (13,541), hazelnuts (9645), raw pistachios (7983), almonds (4454), peanuts (3166).
Drinks: green tea (1772), white tea (1742), black tea (1328), mint tea (409).
Link to a list of ORAC values for a range of foods compiled by the US Department of Agriculture.”Orzechy: orzechy włoskie (13 541), orzechy laskowe (9645), pistacje surowe (7983), migdały (4454), orzeszki ziemne (3166).
Napoje: herbata zielona (1772), herbata biała (1742), herbata czarna (1328), herbata miętowa (409).
Link do listy wartości ORAC dla szeregu artykułów spożywczych przygotowanej przez Departament Rolnictwa USA
Henryk Różański
A 50 ml espresso contains 50 mg of caffeine, while a 125 ml serving of filtered coffee contains 80–125 mg.
„Swiss sources report the following caffeine content in various drinks:
Espresso, 50 ml: 50 mg of caffeine
A 125 ml cup of filter coffee: 80–125 mg of caffeine
One 200 ml glass of cola: 13–50 mg of caffeine
One 150 ml glass of mate (yerba mate): 25 mg of caffeine
One 125 ml cup of black tea: 30–60 mg of caffeine
One 125 ml cup of cocoa: 2–5 mg of caffeine
Energy drinks (stimulant drinks for athletes and drivers; amounts vary by manufacturer), 200 ml: 1–240 mg of caffeine”Szwajcarskie źródła podają następującą zawartość kofeiny w poszczególnych napojach:
Expresso kawa 50 ml: 50 mg kofeiny
Filiżanka kawy z ekspresu do kawy wyposażonego w filtr 125 ml: 80-125 mg kofeiny
1 szklanka Coli 200 ml: 13-50 mg kofeiny
1 szklanka Mate (Yerba Mate) 150 ml: 25 mg kofeiny
1 filiżanka czarnej herbaty 125 ml: 30-60 mg kofeiny
1 filiżanka kakao 125 ml: 2-5 mg kofeiny
Energy Drinks (napoje energetyczne, pobudzające dla sportowców i kierowców, zależnie od producenta) 200 ml: 1-240 mg kofeiny
Research from PubMed · Europe PMC
We selected 4 studies with the best, positive results. This is a selection, not a full review of all research.
Total number of studies on this topic in PubMed: 4 254.
The review indicates that moderate coffee consumption and higher tea consumption, especially green tea, are associated with cardiovascular benefits.
Aim of the study: Coffee and tea are among the most widely consumed beverages worldwide and are the main source of caffeine for adults. In this review, we present findings on the effects of habitual coffee and tea consumption on the prevention of cardiovascular disease (CVD).
Results: In this review, we present findings on the effects of habitual coffee and tea consumption on the prevention of cardiovascular disease (CVD). Mild-to-moderate coffee/caffeine consumption, at 2-3 cups/day, is associated with beneficial effects on metabolic syndrome, including hypertension and diabetes mellitus, although it may raise lipid levels. Furthermore, coffee consumption reduces the risk of coronary heart disease, heart failure, arrhythmia, stroke, CVD, and death from any cause. Higher tea consumption, particularly green tea, offers cardiovascular benefits similar to those of coffee, with 3 cups/day associated with improved survival in population-based studies.
Money for the studycompany together with others · Biosense Webster, National Health and Medical Research Council
Do the authors have ties to companies?not stated
Did a manufacturer help with the study?YES
Type of studydiscussion of other studies
“Not stated” does not mean nobody paid — the database does not always record it.
A cohort study found that moderate coffee consumption and moderate or high tea consumption were associated with slower decline in some cognitive functions.
Aim of the study: Background: Coffee and tea are widely consumed around the world and may provide neuroprotection through anti-inflammatory and antioxidant effects. Objective: This study aimed to investigate associations between coffee and tea intake and cognitive function. Methods: In a longitudinal prospective cohort study, older adults from the UK Biobank who were free of dementia (n = 8715; age range 60.0-85.2 years) reported their coffee and tea intake over the previous year as 'never', 'moderate' (1-3 cups/day), or 'high' (≥4 cups/day).
Results: Background: Coffee and tea are widely consumed around the world and may provide neuroprotection through anti-inflammatory and antioxidant effects. Objective: This study aimed to investigate associations between coffee and tea intake and cognitive function. Methods: In a longitudinal prospective cohort study, older adults from the UK Biobank who were free of dementia (n = 8715; age range 60.0-85.2 years) reported their coffee and tea intake over the previous year as 'never', 'moderate' (1-3 cups/day), or 'high' (≥4 cups/day). Participants completed cognitive assessments at ≥2 timepoints (mean of 9.11 years). Results: Those who 'never' consumed coffee and those with 'moderate' coffee consumption (β = 0.06, p = 0.005; β = 0.07, p < 0.001, respectively), as well as those with 'moderate' and 'high' tea consumption (β = 0.06, p = 0.009; β = 0.06, p = 0.003, respectively), had slower declines in fluid intelligence.
Money for the studygovernment, public institutions · The National Health and Medical Research Council, Western Australian Near-Miss Award
Do the authors have ties to companies?not stated
Did a manufacturer help with the study?NO
Type of studyobservation of people
Participants8 715
“Not stated” does not mean nobody paid — the database does not always record it.
Low coffee or tea consumption was associated with better lung function and a lower risk of COPD, while coffee was also associated with a lower risk of asthma.
Aim of the study: Introduction: Previous studies suggest non-linear associations between tea and coffee intake and respiratory health, with lower risks at low-to-moderate intakes but higher, unexplored risks at high intakes. This study aims to investigate associations between tea and coffee intake and the risk of chronic obstructive pulmonary disease (COPD) and adult-onset asthma.
Results: Results: Compared with not consuming tea or coffee, low intakes (0.5-2 cups per d) were associated with better lung function, lower inflammation, and a lower risk of incident COPD [HR (95% CI); tea: 0.87 (0.81, 0.93) and coffee: 0.86 (0.82, 0.92)] and asthma [coffee: 0.90 (0.85, 0.95)]. A higher risk of COPD was seen with high tea, but not coffee, intake when analyses were restricted to never smokers, but not when participants with respiratory symptoms at baseline were excluded. Conclusion: Both tea and coffee can be part of a healthy diet when consumed in moderation (∼2 cups per d). The lack of a beneficial association at high intakes may be due to residual confounding from smoking for coffee and, in part, reverse causation for tea.
Money for the studygovernment, public institutions · Department of Agriculture, Environment and Rural Affairs, National Health and Medical Research Council
Do the authors have ties to companies?not stated
Did a manufacturer help with the study?NO
Type of studyobservation of people
Participants366 869
“Not stated” does not mean nobody paid — the database does not always record it.
A meta-analysis suggested that higher coffee or tea consumption is associated with a lower risk of cancer progression, particularly colorectal cancer.
Aim of the study: Coffee and tea intake has been suggested to improve survival in cancer patients, but studies published so far have produced conflicting results. This systematic review and meta-analysis aimed to summarize the existing evidence on the association between coffee and tea consumption and cancer survival across different types of cancer.
Results: Overall, a protective effect of coffee and tea consumption on cancer survival was suggested. High coffee and/or tea intake was associated with a 24% reduction in the risk of cancer progression (SHR = 0.76, 95% CI 0.67-0.87, I2 = 57%). Subgroup analysis indicated a stronger protective effect for tea consumption (SHR = 0.64, 95% CI 0.44-0.92, I2 = 45%) than for coffee. The strongest evidence was found for colorectal cancer (SHR = 0.75, 95% CI 0.68-0.83, I2 = 12%); for breast cancer, only tea consumption showed a significant reduction in risk. Dose-response meta-analysis found that each additional cup of coffee/tea significantly reduced the risk of colorectal and breast cancer progression (SHR = 0.93, 95% CI: 0.91-0.95, I2 = 0% and SHR = 0.89, 95% CI: 0.81-0.99, I2 = 57%, respectively). No significant effects were observed for prostate cancer, while data on other sites were too limited.
Money for the studygovernment, public institutions · Ministero della Salute
Do the authors have ties to companies?not stated
Did a manufacturer help with the study?NO
Type of studycombined analysis of many studies (meta-analysis)
“Not stated” does not mean nobody paid — the database does not always record it.
Perspectives and opinion materials
The content below presents the authors’ opinions, interpretations and hypotheses. It is not treated as equal to scientific studies and systematic reviews.
Orthomolecular Medicine News Service Opinion material
„Oxalate is produced by many foods in the diet, including spinach (100-200 mg oxalate per ounce of spinach), rhubarb, and beets.[8-10] Tea and coffee are thought to be the largest source of oxalate in the diets of many people, providing up to 150-300 mg/day.[8,11] This is considerably more than would likely be produced by an ascorbate dose of 1000 mg/day.[5,12] The study we are discussing did not tabulate participants' oxalate intake, but on average they had relatively high intakes (several cups) of tea and coffee.”Oxalate is generated by many foods in the diet, including spinach (100-200 mg oxalate per ounce of spinach), rhubarb, and beets.[8-10] Tea and coffee are thought to be the largest source of oxalate in the diet of many people, up to 150-300 mg/day.[8,11] This is considerably more than would likely be generated by an ascorbate dose of 1000 mg/day.[5,12] The study we are discussing didn't tabulate the participants' intake of oxalate, but on average they had relatively high intakes (several cups) of tea and coffee.
Orthomolecular Medicine News Service Opinion material
„Moyer L (2025) How much caffeine is in coffee, tea, soda, and other foods? Center for Science in the Public Interest. Hamblin MR (2017) Mechanisms and applications of the anti-inflammatory effects of photobiomodulation. AIMS Biophys 4:337-361. Cheng RZ (2025) May is Sunshine Month: Rediscover the Healing Power of Light. Orthomolecular Medicine News Service.”Moyer L (2025) How much caffeine is in coffee, tea, soda, and other foods? Center for Science in the Public Interest. Hamblin MR (2017) Mechanisms and applications of the anti-inflammatory effects of photobiomodulation. AIMS Biophys 4:337-361. Cheng RZ (2025) May is Sunshine Month: Rediscover the Healing Power of Light. Orthomolecular Medicine News Service.
Orthomolecular Medicine News Service Opinion material
„[1,2] Tea and coffee are thought to be the largest source of oxalate in the diets of many people, providing up to 150-300 mg/day. Oxalate is also formed in much smaller quantities by the normal metabolism of ascorbate (vitamin C). High levels of oxalate can cause a common type of kidney stone because oxalate in urine tends to precipitate with calcium to form calcium oxalate crystals. The problem gets worse with inadequate fluid intake. But the typical amount of oxalate ingested in the diet is much more than would be produced by an ascorbate dose of 1000 mg/day. Why have patients with CKD been told to avoid vitamin C supplements?”[1,2] Tea and coffee are thought to be the largest source of oxalate in the diet of many people, up to 150-300 mg/day. Oxalate is also formed in much smaller quantities by the normal metabolism of ascorbate (vitamin C). High levels of oxalate can cause a common variety of kidney stone because oxalate in the urine tends to precipitate with calcium to make crystals of calcium oxalate. The problem gets worse with inadequate liquid intake. But the typical amount of oxalate ingested in the diet is much more than would be generated by an ascorbate dose of 1000 mg/day. Why have CKD patients been told to avoid vitamin C supplementation?
Pisaczek does not judge who is right. It shows what was written and where to read it. Every sentence above has its source.