Health - the seven effects of coffee

 

7 of the weirdest things coffee does to your body

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Emma Beckett, Australian Catholic University

Coffee is best known, and perhaps most valued, for its caffeine and its ability to make us feel more awake and alert.

But coffee is much more than caffeine dissolved in hot water.

Coffee is a chemically complicated plant extract containing hundreds of bioactive compounds. These can have all kinds of weird and wonderful effects in your body, even when you’re drinking decaf.

Here are seven of the strangest.

1. Coffee can make you poo

One study shows about three in ten people say they get the urge to poo shortly after drinking coffee.

This happens quickly, and with both regular and decaf. So it’s down to more than just the caffeine. But it’s not clear exactly which coffee compounds cause this.

Your colon can also be more active in the morning, and this is when most people drink their first coffee.

What you add to your coffee can also affect your bowels. The lactose in milk or some sugar-free sweeteners can also get the bowels moving, particularly if you consume a lot.

2. Coffee can affect your reflux, eyes and ears

Coffee can worsen reflux symptoms for some people. Reflux, when your stomach acid flows back up into your food pipe, isn’t always just felt as heartburn. It can contribute to coughing, wheezing and other respiratory symptoms when reflux affects the throat and airways.

Caffeine can temporarily increase pressure inside the eye in some people with glaucoma or ocular hypertension, where pressure in the eye can already be high. Controlling this pressure is an important part of protecting the major nerve of the eye from damage. So some people with these conditions might be advised to limit their coffee and caffeine intake.

There’s also an ear condition where the tube connecting the middle ear to the back of the nose stays abnormally open, which can make you hear your own voice, or your breathing, unusually loudly. People with this condition, known as patulous Eustachian tube dysfunction, are sometimes advised to drink fewer caffeinated drinks and stay well hydrated, because dehydration can worsen symptoms. However, there is little direct evidence coffee itself causes the condition.

Caffeine’s relationship with migraine is complicated: caffeine can help relieve a migraine, but too much, or suddenly having less than usual, can trigger one in some people.

3. Coffee can interact with your medicines

Coffee can change the way some medicines behave in the body. For instance, it can reduce absorption of the thyroid medication levothyroxine and the osteoporosis drug alendronate.

Caffeine can slow the metabolism of the antipsychotic clozapine, increasing its concentration in the blood.

Sometimes medicines change the way your coffee behaves. For example, the antibiotic ciprofloxacin slows your breakdown of caffeine. So, your usual coffee may stay in your system for longer.

4. Coffee can affect your cholesterol

Coffee contains compounds called diterpenes. Two of these, cafestol and kahweol, can increase total and LDL (“bad”) cholesterol.

But in short-term trials, the same compounds lower lipoprotein(a), which may indicate a lower risk of a heart attack or stroke.

Other coffee compounds, including chlorogenic acids, may modestly lower blood pressure and improve blood vessel function.

So overall, it’s unclear what coffee means for markers of heart health.

5. Coffee may feed your gut microbes

You’re not the only one getting something from your coffee. Laboratory experiments suggest your gut microbes do too.

Some of coffee’s chlorogenic acids aren’t absorbed in the small intestine and reach the colon. There, microbes break them down into other compounds.

Coffee contains complex carbohydrates and roasting products called melanoidins that can reach the colon, where gut microbes can ferment them.

Small human studies suggest drinking coffee can also change the composition of the gut microbiome. But the evidence is still developing, so it’s too early to call coffee a prebiotic.

6. Coffee can influence your iron levels

Coffee can also limit how much iron you get from your food. Drinking coffee with a meal can substantially reduce the absorption of non-haem iron – the form found mainly in plant foods.

This isn’t primarily a caffeine effect. Polyphenols in coffee, including chlorogenic acids, can bind with iron in the digestive tract, making it harder to absorb.

This matters most for people who already have low iron stores or rely heavily on plant sources of iron, rather than being a reason for everyone to give up coffee with breakfast.

7. Coffee can kick-start the gut

Coffee can kick parts of your digestive system into action even when there’s no food to digest. It can stimulate the pancreas to release trypsin, an enzyme involved in digesting protein.

This happens with both regular and decaffeinated coffee, suggesting other compounds in your cup are talking to your digestive system.

Whether this digestive “heads-up” changes how hungry you feel isn’t clear.

Coffee can also affect gut hormones involved in appetite and fullness. But studies haven’t consistently shown whether this translates into eating more or less.

So, what does all this mean?

Caffeine and feeling more alert might be coffee’s most popular feature, but this is far from the whole story. Caffeine can do much more than that.

A cup of coffee contains hundreds of compounds that can interact with our digestive system, microbes, medicines, nutrients and more – sometimes in confusing and unexpected ways.

Emma Beckett, Senior Lecturer, Nutrition and Food Science, Australian Catholic University

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

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.