Health and coffee

Does coffee raise your blood pressure? Here’s how much it’s OK to drink

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Clare Collins, University of Newcastle

Coffee first entered human lives and veins over 600 years ago.

Now we consume an average of almost two kilos per person each year – sometimes with very specific preferences about blends and preparation methods. How much you drink is influenced by genes acting on your brain’s reward system and caffeine metabolism.

Coffee can raise your blood pressure in the short term, especially if you don’t usually drink it or if you already have high blood pressure.

But this doesn’t mean you need to cut out coffee if you have high blood pressure or are concerned about your heart health. Moderation is key.

So how does coffee affect your blood pressure? And if yours is high, how much is OK to drink?

What is high blood pressure?

Blood pressure is the force blood exerts on artery walls when your heart pumps. It’s measured by two numbers:

• the first and biggest number is systolic blood pressure, which is the force generated when your heart contracts and pushes blood out around your body

• the lower number, diastolic blood pressure, is the force when your heart relaxes and fills back up with blood.

Normal blood pressure is defined as systolic blood pressure of less than 120 millimeters of mercury (mm Hg) and diastolic blood pressure of less than 80 mm Hg.

Once your numbers consistently reach 140/90 or more, blood pressure is considered high. This is also called hypertension.

Knowing your blood pressure numbers is important because hypertension doesn’t have any symptoms. When it goes untreated, or isn’t well-controlled, your risk of heart attacks and strokes increases, and existing kidney and heart disease worsens.

About 31% of adults have hypertension with half unaware they have it. Of those taking medication for hypertension, about 47% don’t have it well-controlled.

How does coffee affect blood pressure?

Caffeine in coffee is a muscle stimulant that increases the heart rate in some people. This can potentially contribute to an irregular heartbeat, known as arrhythmia.

Caffeine also stimulates adrenal glands to release adrenaline. This makes your heart beat faster and your blood vessels to constrict, which increases blood pressure.

Blood caffeine levels peak between 30 minutes and two hours after a cup of coffee. Caffeine’s half-life is 3–6 hours, meaning blood levels will reduce by about half during this time.

The range is due to age (kids have smaller, less mature livers so can’t metabolise it as fast), genetics (people can be fast or slow metabolisers) and whether you usually drink it (regular consumers clear it faster).

The impact of caffeine on blood pressure from coffee (and cola, energy drinks and chocolate) varies. Research reviews report increases in systolic blood pressure of 3–15 and a diastolic blood pressure increase of 4–13 after consumption.

The effect of caffeine also depends on a person’s usual blood pressure. An increase in blood pressure may be more risky if you have hypertension and existing heart or liver disease, so it’s best to discuss your coffee consumption with your doctor.

What else is in coffee?

Coffee contains hundreds of phytochemicals: compounds that contribute flavour, aroma, or influence health and disease.

Phytochemicals that directly affect blood pressure include melanoidins, which regulate the body’s fluid volume and activity of enzymes that help control blood pressure.

Quinic acid is another phytochemical shown to lower systolic and diastolic blood pressure by improving the lining of blood vessels, allowing them to better accommodate blood pressure rises.

Can coffee cause hypertension?

In a review of 13 studies that included 315,000 people, researchers examined associations between coffee intake and the risk of hypertension.

During study follow-up periods, 64,650 people developed hypertension, with the researchers concluding coffee drinking was not associated with an increased risk of developing the condition.

Even when they examined data by gender, amount of coffee, decaffeinated versus caffeinated, smoking or years of follow-up, coffee was still not associated with an increased risk of developing hypertension.

The only exceptions suggesting lower risk were for five studies from the United States and seven low-quality studies, meaning those results should be interpreted with caution.

A separate Japanese study followed more than 18,000 adults aged 40–79 years for 18.9 years. This included about 1,800 people who had very high blood pressure (grade 2-3 hypertension), with systolic blood pressure of 160 or above or diastolic blood pressure of 100 or above.

Here, risk of dying from cardiovascular disease, including heart attack or stroke, was double among those drinking two or more cups of coffee a day compared to non-drinkers.

There were no associations with death from cardiovascular disease for those who had either normal blood pressure or mild (grade 1) hypertension (systolic blood pressure 140–159 or diastolic blood pressure 90–99).

The bottom line

There is no need to give up coffee. Here’s what to do instead:

1. know your blood pressure, health history and which food and drinks contain caffeine

2. consider all factors that influence your blood pressure and health – family history, diet, salt and physical activity – so you can make informed decisions about what you consume and how much you move

3. be aware of how caffeine affects you and avoid it before having your blood pressure measured

4. avoid caffeine in the afternoon so it doesn’t affect your sleep

5. aim to moderate your coffee intake by drinking four cups or less a day or switching to decaf

6. if you have systolic blood pressure of 160 or above or diastolic blood pressure of 100 or above, consider limiting to one cup a day, and talk to you doctor.

Clare Collins, Laureate Professor in Nutrition and Dietetics, University of Newcastle

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Artificial intelligence: fast html code of comets example

The example above is html coding done by AI in 1 second to show comets crossing the sky.

Environment - Microplastics have been located at every level of the world's oceans

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Microplastics have been found throughout the world's oceans and at all levels of the water column following a comprehensive survey of over 1,885 sites across the planet. The survey conducted by researchers from Japan, China, New Zealand, Italy, the Netherlands and the United States located microplastics across depths in the ocean including the deepest parts. The Mariana Trench, for example, recorded more than 13,000 microplastic particles per cubic metre nearly 7 miles down. 

Of particular concern from the findings, is that the smallest particles were distributed almost evenly throughout the water currents, rather than being more at the surface level than at the bottom of the ocean.  Another key finding from the survey measurements is that the polymers in these plastics were accounting for very strong reading of the carbon in the water. At depths of 2,000 metres, the polymers comprise as much as 5 per cent of the carbon. 

These high carbon levels may reduce the capacity of oceans to aborb carbon dioxide from the atmosphere and thus enable global warming.

The full report can be accessed here: Microplastics in the ocean

Artificial intelligence: A glowing sun: coded by AI in 0.5s

Easter 2026 - customs

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The Easter period for Christians celebrates the resurrection of Jesus from the dead, a chief tenet of their faith. It's a period of holidays, religious practices, rituals and the consumption of specific food such as hot cross buns and chocolate eggs (or chocolate rabbits/bunnies is another popular practice).  

For the religious faithful, the concept of resurrection is one where, through the faith in God, followers of Jesus are resurrected spiritually and walk a new existence through eternal salvation and dwell in the Kingdom of Heaven.

The custom of Easter eggs is a symbol of life and rebirth and connected with the empty tomb upon the resurrection of Jesus. Eggs were previously chicken eggs dyed in different colours, but in recent decades took on a sweet form through the use of chocolate. In orthodox religions, dyed eggs are still the common practice.

The hot cross bun or spiced bun is made with fruit marked with a cross on the top. Traditionally eaten on Good Friday in the Christian calendar, the bun marks the commencement of the season of Lent. Parts of the bun have different meanings however the cross on the top is umistakeable as the crucifixion of Jesus. The bun has a long history stretching back to the 6th Century with variations occuring in the centuries thereafter.

May the period of Easter be one of reflection and celebration in a conflicted world.

Climate change - the world continues to heat up

 

The latest world climate report is grim, but it’s not the end of the story

Andrew King, The University of Melbourne

It’s no secret our planet is heating up.

And here’s the evidence: we’ve just experienced the 11 hottest years on record, with 2025 being the second or third warmest in global history.

The annual State of the Climate report, published today by the World Meteorological Organization, suggests we’re still too reliant on fossil fuels. And that’s pushing us further from our goal to decarbonise.

So what is happening to our climate? And how should we respond?

The climate picture

Unfortunately, the most recent climate data makes for grim reading.

Let’s look back at 2025, through the lens of four climate change indicators.

Carbon dioxide

We now have a record amount of carbon dioxide in the atmosphere, about 50% higher than pre-industrial levels. And we’re still emitting large amounts of carbon dioxide through our use of fossil fuels. In 2025, global emissions reached record high levels. The carbon dioxide we emit can stay in the atmosphere for a long time. So each year we keep emitting large amounts of carbon dioxide, the more concentrated it will be in our atmosphere.

Temperature

In 2025, the world experienced its second or third warmest year on record, depending on which dataset you use. The average temperature was about 1.43°C above the pre-industrial average.

This is particularly unusual given we observed slight La Niña conditions in the Pacific region. La Niña is a type of climate pattern characterised by temperature changes in the Pacific Ocean. It typically creates milder, wetter conditions in Australia and has a cooling effect on the global average temperature. But even with La Niña conditions, the planet stayed exceptionally hot.

And each of the last 11 years were hotter than any of the previous years in the global temperature series. This is true across all the different datasets used in the report. However, this does not mean a new record was set each year.

Oceans and ice

In 2025, the heat held within the world’s oceans reached a record high. And as our oceans continue to warm, sea levels will also rise. Hotter oceans also speed up the process of acidification, where oceans absorb an increased amount of carbon dioxide with potentially devastating consequences for some marine animals.

The amount of Arctic and Antarctic ice is also well below average. This report shows sea ice extent, a measure of how much ocean is covered by at least some sea ice, is at or close to record low levels in the Arctic. Meanwhile, the amount of ice stored in glaciers has also significantly decreased.

Extreme weather

Research shows many of the most devastating extreme weather events of 2025 were exacerbated by human-driven climate change. The heatwaves in Central Asia, wildfires in East Asia and Hurricane Melissa in the Carribean are just three examples. Through attribution analysis, which is how scientists determine the causes of an extreme weather or climate event, this report highlights how our greenhouse gas emissions are making severe weather events more common and intense.

How does Australia stack up?

Compared to most other countries, Australia has a disproportionate impact on the global climate.

This is largely because our per capita carbon dioxide emissions are about three times the global average. That means on average, each of us emits more carbon dioxide than people in all European countries and the US.

Emissions matter because they exacerbate the greenhouse effect. That is the process by which greenhouse gases, such as carbon dioxide and methane, trap heat near Earth’s surface. So by emitting more greenhouse gases, we contribute to global warming. And research suggests Earth is warming twice as fast today, compared to previous decades.

However, Australia is also experiencing first-hand the adverse effects of human-induced climate change.

In 2025, we lived through our fourth-warmest year on record. The annual surface temperatures of the seas around Australia reached historic highs, beating the record temperatures set in 2024. And last March was the hottest March we’ve seen across the continent.

Here in Australia, we are also battling longer and hotter heatwaves and bushfire seasons. And scientists warn these extreme weather events will only become more common.

The Bureau of Meteorology’s annual summary highlights how Australia’s climate is changing.

So what can we do?

The 2025 State of the Climate Report shows how much, and how quickly, we are changing our climate. And it is worryingly similar to previous reports, highlighting the need for urgent action.

The priority should be decreasing our emissions. This would slow down global warming, which will only continue if we keep the status quo. Some countries are already decarbonising rapidly, in part through transitioning to renewable electricity supplies. Others, including Australia, need to move much faster to reduce emissions.

Crucially, we must also meet our net zero targets. In Australia, as in many other countries, we are aiming to reach net zero by 2050. The sooner we reach net zero, the more likely we are to avoid harmful climate change impacts in future. To achieve net zero, we need to significantly reduce our emissions while also increasing how much carbon we remove from the atmosphere.

Even if we meet our net zero targets, climate change will not magically disappear. However, by turning away from fossil fuels and cutting our greenhouse gas emissions now, we may spare future generations from its worst effects. That’s the least we can do.

Andrew King, ARC Future Fellow and Associate Professor in Climate Science, ARC Centre of Excellence for 21st Century Weather, The University of Melbourne

This article is republished from The Conversation under a Creative Commons license. Read the original article.