Coffee, health and caffeine

Coffee and sleep

Caffeine can affect sleep. The European Food Safety Authority says a single 100 mg dose may affect sleep duration and patterns in some adults, particularly close to bedtime; the NHS's advice for insomnia is to avoid tea and coffee for at least six hours before bed.

Regulatory guidance·Associated with increased risk/effect

Two official statements, read for this page. EFSA's 2015 opinion, as the authority summarises it, says single doses of 100 mg of caffeine may affect sleep duration and patterns in some adults, particularly when consumed close to bedtime. The NHS's page on insomnia tells people who have it not to drink tea or coffee for at least six hours before going to bed. Neither gives a time that suits everyone, and this page does not either.

Limitations and confounders

The NHS advice is written for people who have insomnia, not for everyone. EFSA's statement says "some adults": people differ in how caffeine affects them, and neither document gives a figure for how long it stays active.

This is general information, not personalised medical advice. It does not diagnose, treat or replace professional care. If you have a specific medical condition, take medication, are pregnant or breastfeeding, or have symptoms that concern you, speak with a doctor, pharmacist or other qualified healthcare professional.

Coffee, anxiety and jitteriness

The US Food and Drug Administration lists anxiety and jitters among the symptoms too much caffeine can cause, and says some conditions and medicines make people more sensitive to it.

Regulatory guidance·Associated with increased risk/effect

The FDA's consumer guidance says too much caffeine can cause a variety of symptoms, among them increased heart rate, palpitations, insomnia, anxiety, jitters, upset stomach, nausea and headache, and that certain conditions and some medications tend to make people more sensitive to caffeine's effects. It does not say at what amount any one person will notice them. This page does not diagnose anxiety; persistent or severe symptoms are a matter for a healthcare professional whatever your coffee intake.

Limitations and confounders

The guidance describes what too much caffeine can do, not what a given cup will do. It names no threshold for sensitive people.

This is general information, not personalised medical advice. It does not diagnose, treat or replace professional care. If you have a specific medical condition, take medication, are pregnant or breastfeeding, or have symptoms that concern you, speak with a doctor, pharmacist or other qualified healthcare professional.

Coffee and blood pressure

The NHS's guidance on high blood pressure advises not drinking too much caffeine, and names coffee, tea and cola as drinks high in it. The FDA lists high blood pressure among the effects of too much caffeine.

Clinical guidance·Associated with increased risk/effect

The NHS's page on high blood pressure includes, among the things to avoid, drinking too much caffeine; it gives no amount. The FDA's consumer guidance lists high blood pressure among the symptoms too much caffeine can cause. Neither document, as read for this page, says how large or how lasting the effect of a cup is, or whether regular drinkers are affected less, so this page does not say so either. If you have diagnosed high blood pressure, follow your own clinician's guidance, and never adjust medication on the strength of this page.

Limitations and confounders

Both documents speak of "too much" without defining it. No study of the size or duration of the effect was read for this page.

This is general information, not personalised medical advice. It does not diagnose, treat or replace professional care. If you have a specific medical condition, take medication, are pregnant or breastfeeding, or have symptoms that concern you, speak with a doctor, pharmacist or other qualified healthcare professional.

Coffee and heart health

A 2017 review of the published meta-analyses found coffee drinking more often associated with benefit than harm, including for cardiovascular outcomes, and called most of that evidence low or very low quality. Separately, the FDA lists a raised heart rate and palpitations among the effects of too much caffeine.

Systematic review·Mixed or uncertain evidence

The review, published in the BMJ, pooled existing meta-analyses of observational studies. Its authors conclude that coffee consumption seems generally safe within usual levels of intake, and in the same paper say that most of the evidence is observational and of low or very low quality, that residual confounding could explain the associations, and that genetic studies found no evidence that the association with lower cardiovascular mortality is causal. It is not evidence that coffee protects the heart. The FDA's guidance, separately, lists increased heart rate and palpitations among the symptoms of too much caffeine. Anyone with a diagnosed heart or rhythm condition should follow their clinician's advice.

Limitations and confounders

Associations in population studies, which the review's own authors say may be produced by confounding. Read by passage, not in full; its tables were not read.

This is general information, not personalised medical advice. It does not diagnose, treat or replace professional care. If you have a specific medical condition, take medication, are pregnant or breastfeeding, or have symptoms that concern you, speak with a doctor, pharmacist or other qualified healthcare professional.

Coffee, cholesterol and filtering

Paper-filtered coffee carries far less of two coffee-oil compounds, cafestol and kahweol, than unfiltered brews such as French press, Turkish and boiled coffee. That is a measurement. What it means for anyone's cholesterol is a question this page does not answer.

Laboratory study·Mixed or uncertain evidence

Cafestol and kahweol are diterpenes found in coffee oil, and laboratory measurements find far less of them in paper-filtered coffee than in unfiltered brews. A pooled analysis of fourteen trials, published in 2001, concluded that unfiltered coffee, and not filtered coffee, raises total and LDL cholesterol. CoffeeHQ has read that analysis only in summary, so it does not state the size of the effect or what anyone should drink because of it. If you are managing your cholesterol, ask your doctor or pharmacist whether how your coffee is brewed matters for you.

Limitations and confounders

The amounts in the cup were read in full; the pooled trials of coffee and blood lipids were read only in summary. The size of any effect on cholesterol, and how it depends on how much is drunk, was not read.

This is general information, not personalised medical advice. It does not diagnose, treat or replace professional care. If you have a specific medical condition, take medication, are pregnant or breastfeeding, or have symptoms that concern you, speak with a doctor, pharmacist or other qualified healthcare professional.

Coffee, heartburn and acid reflux

The NHS lists coffee, with tomatoes, alcohol, chocolate and fatty or spicy foods, among the food and drink that can cause heartburn and acid reflux or make them worse.

Clinical guidance·Associated with increased risk/effect

That list is on the NHS's page on heartburn and acid reflux, under causes. The page gives no amount and does not single coffee out in its advice. The FDA's guidance separately lists upset stomach and nausea among the effects of too much caffeine. Other things often said about coffee and digestion, including its effect on bowel movement, are not covered by anything read for this page, so they are not stated here. Recurring heartburn or digestive discomfort is worth raising with a healthcare professional.

Limitations and confounders

A list of possible triggers in patient guidance, not a measured effect. What triggers symptoms differs from person to person.

This is general information, not personalised medical advice. It does not diagnose, treat or replace professional care. If you have a specific medical condition, take medication, are pregnant or breastfeeding, or have symptoms that concern you, speak with a doctor, pharmacist or other qualified healthcare professional.

Coffee and hydration

Coffee counts towards daily fluid intake in the NHS's guidance on drinks. One controlled study of fifty men who habitually drank coffee found no difference in body water between three days of moderate coffee drinking and three days of water.

Randomised trial evidence·No clear effect shown

The NHS's guidance says water, lower-fat milk and lower-sugar drinks, including tea and coffee, all count towards daily fluid intake, and advises drinking caffeine in moderation because people differ in how sensitive they are to it. The study, published in 2014, gave fifty men who usually drank three to six cups a day four 200 mL cups of coffee daily in one period and the same volume of water in another, and found no significant change in total body water in either. Its authors conclude that coffee, drunk in moderation by men used to caffeine, provides similar hydrating qualities to water.

Limitations and confounders

The study was of men who already drank coffee daily, over three days per arm, at about 308 mg of caffeine a day. It says nothing about women, people unused to caffeine, larger amounts, heat or exercise.

This is general information, not personalised medical advice. It does not diagnose, treat or replace professional care. If you have a specific medical condition, take medication, are pregnant or breastfeeding, or have symptoms that concern you, speak with a doctor, pharmacist or other qualified healthcare professional.

Coffee, caffeine and headaches

The FDA lists headache among the symptoms too much caffeine can cause, and says withdrawal from caffeine can be unpleasant.

Regulatory guidance·Mixed or uncertain evidence

Both statements are in the FDA's consumer guidance: headache appears in its list of symptoms of too much caffeine, and it describes caffeine withdrawal as not dangerous but possibly unpleasant, advising people who want to cut back to do so gradually. The guidance read for this page does not say that caffeine relieves headaches, and it gives no treatment for them; nor does this page. Recurring or severe headaches warrant a medical assessment.

Limitations and confounders

Consumer guidance, not a study of headache. Migraine is a separate condition that nothing read for this page addresses.

This is general information, not personalised medical advice. It does not diagnose, treat or replace professional care. If you have a specific medical condition, take medication, are pregnant or breastfeeding, or have symptoms that concern you, speak with a doctor, pharmacist or other qualified healthcare professional.

Caffeine dependence and withdrawal

Regular caffeine use is followed, in many people, by unpleasant withdrawal symptoms when it stops abruptly; official consumer guidance advises cutting back gradually.

Regulatory guidance·Associated with increased risk/effect

The US Food and Drug Administration's consumer guidance says caffeine withdrawal is not considered dangerous but can be unpleasant, and that anyone used to caffeine every day who wants to cut back does best to do so gradually. How long symptoms last is not stated there and is not stated here.

Limitations and confounders

The guidance gives no duration and no list of who is affected.

This is general information, not personalised medical advice. It does not diagnose, treat or replace professional care. If you have a specific medical condition, take medication, are pregnant or breastfeeding, or have symptoms that concern you, speak with a doctor, pharmacist or other qualified healthcare professional.

Coffee, pregnancy and breastfeeding

The NHS advises no more than 200 mg of caffeine a day in pregnancy and recommends the same figure while breastfeeding, counting every source and not coffee alone. Limits are set nationally and differ between countries.

Regulatory guidance·Associated with increased risk/effect

In the United Kingdom the NHS says you should not have more than 200 mg of caffeine a day in pregnancy, and gives about 100 mg for a cup of instant coffee, noting that filter coffee and coffee from coffee shops can contain more. It says too much caffeine has been linked to a higher chance of miscarriage and stillbirth. For breastfeeding, the NHS says caffeine can reach a baby through breast milk and recommends no more than 200 mg a day, while saying there is not enough information to say how much is too much. The European Food Safety Authority's 2015 opinion found intakes up to 200 mg a day raise no safety concern for the foetus. The FDA recommends talking to a healthcare provider. Follow your own midwife's or doctor's advice.

Limitations and confounders

Serving sizes vary a great deal, so counting cups is less reliable than counting caffeine. The figures are national guidance, not a personal limit.

This is general information, not personalised medical advice. It does not diagnose, treat or replace professional care. If you have a specific medical condition, take medication, are pregnant or breastfeeding, or have symptoms that concern you, speak with a doctor, pharmacist or other qualified healthcare professional.

Coffee, caffeine and children

The FDA says too much caffeine in children and teenagers can cause a raised heart rate, palpitations, high blood pressure, anxiety, and sleep and digestive problems. The European Food Safety Authority proposes 3 mg per kilogram of body weight a day as a level of habitual intake raising no safety concern.

Regulatory guidance·Associated with increased risk/effect

Both statements come from the documents named. The FDA's list for children and teenagers also includes dehydration. EFSA's figure, from its 2015 opinion as the authority summarises it, is a level proposed as raising no safety concern for habitual consumption by children and adolescents; it is not a recommendation to give children caffeine. Neither document says anything about coffee and growth, and this page does not either. A child's doctor is the right source for advice about a particular child.

Limitations and confounders

Caffeine reaches children from soft drinks, energy drinks and chocolate as well as coffee; the documents concern caffeine from all sources.

This is general information, not personalised medical advice. It does not diagnose, treat or replace professional care. If you have a specific medical condition, take medication, are pregnant or breastfeeding, or have symptoms that concern you, speak with a doctor, pharmacist or other qualified healthcare professional.

Coffee and long-term disease risk: an overview

Population studies more often associate coffee drinking with lower than with higher risk of several diseases, and the authors of the largest review of them call most of that evidence low or very low quality. The World Health Organization's cancer agency found no conclusive evidence that drinking coffee causes cancer.

Systematic review·Mixed or uncertain evidence

A 2017 review in the BMJ of existing meta-analyses found coffee consumption more often associated with benefit than harm across a range of health outcomes, and concluded it seems generally safe within usual levels of intake. The same authors write that most of the evidence comes from observational research of low or very low quality, that residual confounding could produce the associations, and that genetic studies found no evidence the associations with type 2 diabetes and with mortality are causal. They also report that drinking coffee in pregnancy seems associated with low birth weight, preterm birth and pregnancy loss, and that high consumption was associated with a higher risk of fracture in women. None of this shows that coffee prevents or treats any disease. On cancer, the International Agency for Research on Cancer in 2016 moved coffee drinking to Group 3, not classifiable as to its carcinogenicity, after reviewing more than 1,000 studies; it found reduced risks for cancers of the liver and the lining of the womb and inconclusive evidence for more than twenty others. The same evaluation classed drinking very hot beverages, above 65 °C, as probably carcinogenic to the oesophagus: a finding about temperature, not about coffee.

Limitations and confounders

Associations, not causes. The review was read by passage and its tables not at all; the cancer evaluation was read from the agency's press release, not the monograph.

This is general information, not personalised medical advice. It does not diagnose, treat or replace professional care. If you have a specific medical condition, take medication, are pregnant or breastfeeding, or have symptoms that concern you, speak with a doctor, pharmacist or other qualified healthcare professional.

Coffee and medicines

Some medicines make people more sensitive to caffeine, the FDA's consumer guidance says. Which medicines, and what to do about it, is a question for a pharmacist or doctor.

Regulatory guidance·Mixed or uncertain evidence

The FDA's guidance says certain conditions tend to make people more sensitive to caffeine's effects, as can some medications. It names none, and this page names none: no list of interacting medicines was read for it. If you take any medicine, ask the pharmacist or doctor who knows what you take whether caffeine matters, and read the leaflet that came with it.

Limitations and confounders

One general sentence in consumer guidance. It does not say which medicines or how.

This is general information, not personalised medical advice. It does not diagnose, treat or replace professional care. If you have a specific medical condition, take medication, are pregnant or breastfeeding, or have symptoms that concern you, speak with a doctor, pharmacist or other qualified healthcare professional.

Coffee, iron and nutrient absorption

Large amounts of tea and coffee make it harder for the body to absorb iron, according to the NHS's guidance on iron deficiency anaemia, which lists them with milk and dairy among things to have less of.

Clinical guidance·Associated with increased risk/effect

The NHS's page on iron deficiency anaemia advises people who have it to eat and drink less tea, coffee, milk and dairy, because large amounts make it harder for the body to absorb iron. It gives no amount and no timing rule, and this page gives none. If you have, or think you may have, low iron, the advice to follow is your own doctor's.

Limitations and confounders

Guidance for people with the condition, not a study of absorption. It does not say how much is a large amount.

This is general information, not personalised medical advice. It does not diagnose, treat or replace professional care. If you have a specific medical condition, take medication, are pregnant or breastfeeding, or have symptoms that concern you, speak with a doctor, pharmacist or other qualified healthcare professional.

Coffee, caffeine and trying to conceive

The FDA recommends that anyone pregnant, trying to become pregnant or breastfeeding talk to their healthcare provider about whether to limit caffeine.

Regulatory guidance·Mixed or uncertain evidence

That recommendation is the only statement about trying to conceive in the documents read for this page. No study of caffeine and fertility was read, so nothing is said here about whether caffeine affects it. For the limits that apply once pregnant, see the entry on pregnancy and breastfeeding.

Limitations and confounders

A recommendation to ask, not a finding.

This is general information, not personalised medical advice. It does not diagnose, treat or replace professional care. If you have a specific medical condition, take medication, are pregnant or breastfeeding, or have symptoms that concern you, speak with a doctor, pharmacist or other qualified healthcare professional.

Coffee and menopause

The NHS suggests avoiding or reducing potential triggers of hot flushes and night sweats, and names caffeine among them, with spicy food, hot drinks, smoking and alcohol.

Clinical guidance·Mixed or uncertain evidence

The suggestion is on the NHS's page of things you can do about menopause symptoms. It calls these potential triggers; it does not say that caffeine causes hot flushes or that everyone is affected, and it gives no amount.

Limitations and confounders

A list of potential triggers in patient guidance. No study of caffeine and menopause symptoms was read.

This is general information, not personalised medical advice. It does not diagnose, treat or replace professional care. If you have a specific medical condition, take medication, are pregnant or breastfeeding, or have symptoms that concern you, speak with a doctor, pharmacist or other qualified healthcare professional.