Health benefits of tea and coffee

04 January 2021

Your daily cup of tea or coffee could prove a potent brew of health benefits. We take a look at the research findings that link tea and coffee with better health.



For every cup of tea or coffee you drink, you take in around 200 mls of fluid, (depending on the size of your cup). About 40% of the nation’s fluid intake comes from tea alone.

Keeping properly hydrated is important. It helps you avoid urinary tract infections (UTIs), and helps to maintain your cognitive functions. That alone would be good enough reason to drink tea and coffee. But as scientists discover more each year, we’re learning that our favourite drinks may offer other important health benefits.

For example, some key findings from early-stage studies on tea and coffee include:

  • Drinking tea or coffee regularly could reduce cognitive decline by as much as 37 percent as you get older.
  • Drinking at least three cups of tea or coffee a day is associated with a reduced risk of Type 2 Diabetes.
  • Drinking coffee may protect you from being diagnosed with a more advanced prostate cancer.
  • Coffee drinkers (four or more cups a day) may have a 39 percent decreased risk of developing mouth and pharynx cancers.
  • Coffee may cut your risk of being hospitalised due to heart rhythm problems.
  • Caffeine may reduce your risk of ovarian cancer.

Is tea good for you?

"Teas - black and green – come from the same plant, Camellia sinensis. They contain active plant compounds called polyphenols (antioxidants), which have heart health and possibly anti cancer benefits too," explains dietitian and nutritionist Dr Carrie Ruxton, a member of the Tea Advisory Panel (TAP).

Polyphenols help to combat oxidation of fats in the blood, and so help protect us against heart disease and their antioxidant action on damaging free radicals protects against some cancers."There’s pretty strong evidence from controlled trials that tea polyphenols relate to a reduced risk of heart disease at around four cups of tea a day," says Dr Ruxton.

How tea helps heart health

A study in the Netherlands found that people who drank three to six cups of tea a day had a 45 percent lower risk of dying from heart disease than those who drank less than one cup of tea a day. People who drank two to four cups of coffee a day had a 20 percent lower risk of heart disease than those who drank less.

"Other studies relate regular tea consumption with a reduced risk of stroke and type 2 diabetes, but these are quite new areas and need more work," she said. It’s harder to make a clear case at the moment for the cancer-fighting properties of tea, simply because it’s hard to carry out reliable trials.

How tea helps your brain

Tea contains two other elements that benefit us. "Caffeine, in moderate doses of 50-450mg per day, is very beneficial for cognitive function," says Carrie Ruxton. "We have good evidence from controlled trials that after drinking tea our memory improves, we have faster reaction times and a better ability to concentrate." So even though tea has about half as much caffeine as coffee (which also gives the little grey cells a boost), it’s enough to make a difference.

Despite old wives' tales to the contrary, the caffeine in tea doesn’t cause dehydration. A recent study revealed, using blood and urine tests, that four cups of tea a day was just as hydrating as a similar amount of water.

How tea helps your gut microbiome

Dr Tim Bond from the Tea Advisory Panel says:

“Both black and green tea contains a number of ingredients, including polyphenols and tannins that interact with the gut microbial flora. Tea polyphenols are typically broken down by the gut microflora and produce secondary metabolites, which can be absorbed. The interaction between tea and the gut microbiota may explain the large number of human trials which report beneficial effects of tea drinking on vascular function, blood pressure, oral and gut pathogens and body fat control.

“Tea has an important role to play in a gut friendly diet, helping to rebalance the gut microbiota, with evidence for a range of different teas including black (regular) tea, green tea, oolong and Pu-erh tea. A recent review of 24 trials found that tea, especially green tea, can exert prebiotic effects and help to improve the health of the gut microflora.

“Tea has been shown to improve the health of the oral microbiome with the oral microbial flora for tea drinkers differing from that of non-tea drinkers. These beneficial changes may contribute to links between tea consumption and reduced risk of various diseases including cancer. ”

Tea and immune function

Tea contains a number of active compounds that may beneficially impact the immune system. “The main active constituents include a high concentration of polyphenols, mainly the flavonoids. The predominant group of flavonoids in tea are the catechins which, together with the amino acid L-theanine found principally in black tea, have been implicated in the positive impacts of tea on the immune system,” says Dr Tim Bond. “Laboratory studies suggest both antibacterial and antiviral effects of these compounds. A 2012 review highlighted laboratory studies that showed reduced viral replication with theanine-related compounds.”

Why tea makes you feel great

Tea contains an amino acid called L-theanine, which is known to make us feel relaxed. "You get a fantastic combination of feeling slightly more alert, with your cognitive functions working a bit harder, and at the same time you’re more relaxed. We’ve known for a long time that tea makes us feel good. But it’s only recently that we’ve known why it has that effect," says Carrie Ruxton.

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New research has, however, found that tea may contain higher concentrations of fluoride than previously realised. Instead of the one to two milligrams of fluoride per litre of black tea that most published reports have shown in the past, the new findings show it may be as high as nine milligrams. This isn’t a problem for most people, who take in two to three milligrams a day from sources such as fluoridated water, toothpaste, tea and food. Really serious tea drinkers on the other hand – those who measure their daily tea intake in gallons, and like it good and strong – may be at risk of skeletal fluorosis, a fairly rare disease that can damage joints and bones.

Green tea benefits

Green tea comes from the same plant as black tea, but is processed differently and doesn’t undergo the oxidation process that gives black tea its distinctive colour and taste. As a result it has higher levels of more simple flavonoids, known as catechins. "It’s easier to extract the catechins from green tea," explains Dr Tim Bond. "So a lot of studies are carried out using green tea extract."

In trials, drinking green tea has been associated with lower risk of death from cardio-vascular disease and colorectal cancer. It may also protect us against eye disease such as glaucoma, but this research is at a very early stage.

Green tea and weight loss

In research green tea has produced weight loss results, albeit very modest. However, if you swap a standard, semi-skimmed caffe latte (95 calories) for the same size cup of black tea with semi-skimmed milk (13 calories), over the course of a year you could lose 8lbs in weight.

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Dip or soak the teabag?

To get the most benefit from your tea, go for a relatively strong brew. Caffeine comes out of tea very quickly, so if you just dip your tea bag in a cup of hot water, you’ll get the caffeine. However the polyphenols have larger molecules, so take longer to come out.

Health benefits of herbal teas

Dr Tim Bond adds: “Herbal tea infusions have a range of health benefits. This is because many are rich sources of natural bioactive compounds, such as alkaloids, carotenoids, and flavonoids. A recent review of clinical trials found evidence for health benefits linked to drinking different herbal tea infusions - one to three cups daily. The review found: improved sleep quality and blood sugar control with chamomile tea: improved hormone control, and less osteoarthritic joint stiffness after drinking spearmint tea and reduced oxidative stress with lemon balm tea.

“Laboratory studies have found antibacterial and antioxidant effects, the ability to help lower inflammation and allergic disposition, relax blood vessels, and possibly help target excessive blood clotting – which is a risk factor for heart disease.”

Health benefits of coffee

The caffeine in coffee – and tea, and caffeinated drinks – is a stimulant, and that’s the substance that perks us up, gets our brain moving and gives us a buzz. There is also evidence that coffee can boost our physical performance and may reduce our risk of depression.

Coffee - one of the most popular drinks in the world - is being subjected to ever-increasing amounts of research. Like tea, coffee is also a good source of polyphenol antioxidants. These mop up the free radicals in our blood, which can cause damage to our bodies. The findings so far indicate that moderate consumption of coffee – four to five cups a day – is fine for most people and may bring health benefits.

Coffee and stroke risk

Recent research has shown some promising results. A study published in February 2009 linked coffee drinking with a reduced risk of stroke in women. The results showed that the more coffee a woman drank, the lower her risk of stroke. However, as with many studies that hit the headlines this research is still in its early stages.

Coffee and Parkinson's disease

Scientists have also found evidence that people who drank two to three cups of coffee a day decreased their risk of developing Parkinson’s disease by up to 25 percent. "These results represent the strongest evidence so far that caffeine may have some protective effects against developing Parkinson’s," says Kieran Breen, Director of Research and Development at the Parkinson’s Disease Society.

Coffee and dementia

Another study, carried out on mice, found that drinking three to five cups of coffee a day in middle age is associated with a 65 percent decrease in risk of developing Alzheimer’s and dementia. Alzheimer’s Research Trust spokesperson, Alison Cranage says "The same team that reported these findings on mice hope to begin human trials of caffeine to see if the findings are replicated in people."

Until the scientists can give us more answers, we have to wait and hope that something as every-day as a cup of tea or coffee could be the magic potion that helps keep us healthy.

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The material is for general information only and does not constitute investment, tax, legal, medical or other form of advice. You should not rely on this information to make (or refrain from making) any decisions. Always obtain independent, professional advice for your own particular situation.