tea and coffee

see also:

• caffeine
• diets and healthy foods

• drinking coffee and tea daily in moderation appear to have a variety of health benefits with significant reductions in all cause mortality
• regular caffeine intake results in tolerance (and also risk of withdrawal symptoms upon cessation):
  • in middle-aged adults who regularly drink coffee, there was little to no association between habitual caffeine intake, sleep quality, and daytime sleepiness¹⁾
  • lower regular intakes (< 750mg/day) result in incomplete tolerance

• coffee's bioactive compounds, particularly caffeine, polyphenols, and diterpenes, exert antioxidant, anti-inflammatory, antifibrotic, gut microbiome-modulating, and epigenetic-regulating effects, thereby slowing the progression of liver damage and reducing the risk of cirrhosis and liver cancer, but this beneficial effect apparently requires at least 3 cups per day ³⁾
• adding milk can reduce the absorption of chlorogenic acids and other polyphenols by more than half - the antioxidant activity of coffee may decrease significantly with just a small amount of milk
  • a mainly milk coffee drink also adds to calorie intake
• 2 cups a day of black coffee (preferably early in the day to avoid caffeine's effects on sleep or GORD) appears to be beneficial, higher intake may have increasing adverse effects
  • although a stimulant, coffee does not appear to increase long term hypertension ⁴⁾
  • nevertheless, those with severe hypertension should probably limit coffee to 1 cup per day as a Japanese studied suggested higher cardiovascular mortality in this subgroup who drank 2 or more cups a day ⁵⁾
• coffee intake may reduce risk of uterine cancer
• coffee intake appears to improve the GIT microbiome⁶⁾
• drinking 3-4 cups a day appears to slow cellular aging (slow the reduction in length of telomeres) in individuals with schizophrenia and affective disorders ⁷⁾
• the gut organism Lawsonibacter asaccharolyticus appears to be mainly found in coffee drinkers⁸⁾
• coffee (even decaffeinated) apparently via muscarinic effects also enhances the gastro-colic effect and the urge to defecate, hence a good reason to have it first thing in the morning
• in a very large UK study over 11 years with avg age 56yrs published in 2021, 0.5-3 cups coffee per day was associated with a 12% reduction in all cause mortality, 17% reduction in mortality from cardiovasc disease, and 21% lower risk of stroke ⁹⁾

• green tea / matcha
  • may have benefits due to its caffeine, antioxidants and catechins like epigallocatechin gallate (EGCG) and L-theanine
    • matcha has greater concentrations of caffeine and L-theanine (50-100% more per cup of brewed tea), more vitamin C, and matcha can contain up to 137 times more antioxidants than low-grade green teas and up to 3 times more antioxidants than high-quality green teas
    • matcha contains notably higher aluminium levels than green or black tea infusions due to consuming the whole leaf powder, which absorbs soil aluminium during shaded growth. Studies report matcha samples ranging 1,743–2,350 mg/kg, potentially exceeding EFSA's TWI (1 mg/kg body weight/week) with 2–3.6g daily intake (e.g., 1–2 portions), even as a sole source. Green and black teas, steeped as leaves, leach far less (<500 mg/kg or <13 µg/mL or < 3mg per 250mL cup in infusions), keeping exposure low¹⁰⁾
    • black teas have about half the amount of EGCG as oxidation converts catechins to theaflavins and thearubigins
  • green tea reduces systolic and diastolic blood pressure, especially in those with baseline systolic ≥130 mm Hg, and lowers total cholesterol and LDL
  • 3-5 cups daily appears to lower stroke risk
  • appears to improve HbA1c in type 2 diabetes with better glucose/insulin levels, and gut microbiome shifts aiding obesity prevention
  • may reduce risk of a range of cancers, may inhibit a range of infections, reduce diarrhoea, reduce cognitive decline but also may reduce iron absorption, and as with black teas, may contain high levels of aluminium while high levels of EGCG may be hepatotoxic, cytotoxic to pancreas, and at extreme doses may induce goitres ¹¹⁾
  • a 12-month RCT found 2g daily matcha improved social acuity (facial emotion perception) and trended toward better sleep quality in older adults with mild cognitive decline.¹²⁾
  • matcha appears to reduce the usual allergen-induced increased expression of c-Fos gene in the ventral spinal trigeminal nucleus caudali with resultant reduction in sneezing ¹³⁾

• drinking 2 cups a day of coffee appears to be beneficial for those with AF or in helping to prevent AF and cardiac failure
  • this study showed a 37% hazard reduction in AF recurrences ¹⁴⁾
  • appears to reduce risk of cardiac failure in patients with AF
  • appears to reduce risk of dementia in those with AF and in those without AF¹⁵⁾
• excessive caffeine intake however may cause rapid AF

• studies suggest that daily drinking coffee or tea reduces risk of osteoporosis by about 17-25% with tea seeming to have the greater benefit however excessive coffee at over 5 cups a day increased osteoporosis risk ¹⁶⁾
• the effect may be due to catechins while caffeine theoretically can interfere with calcium absorption and bone metabolism although this effect appears to be minimal and further reduced by drinking it with milk

• those who drank two cups of coffee every day were at a 70% lower risk of developing polycystic ovary syndrome (PCOS) / polyendocrine metabolic ovarian syndrome (PMOS) symptoms than those who never drank coffee. Mechanistically, this protective role of coffee has been attributed to its effects on the metabolism of sex hormones like testosterone in the plasma. ¹⁷⁾
  • coffee contains high phenol levels that improve insulin sensitivity and alleviate hypersecretion. Reduced expression of the phosphatidylinositol 3-kinase (PI3K) pathway also decreases insulin sensitivity and improves β-cell function.