Are you the type who feels jittery after the caffeine hit of a single espresso — or do you feel unaffected no matter how many coffees you line up?

There are multiple reasons why we all react to caffeine differently. Chief among them is the amount of an enzyme called CYP1A2 in your liver, and that’s down to your genes.

It takes people with lower levels of CYP1A2 longer to break down caffeine; they also feel its stimulating effects more keenly.

But even if you feel you can ‘hold’ your caffeine well, there are good reasons to limit it.

The NHS recommends that adults drink no more than 400 mg per day (for pregnant women, it’s 200 mg).

Are you the type who feels jittery after the caffeine hit of a single espresso ¿ or do you feel unaffected no matter how many coffees? Are you the type who feels jittery after the caffeine hit of a single espresso ¿ or do you feel unaffected no matter how many coffees?

Are you the type who feels jittery after the caffeine hit of a single espresso — or do you feel unaffected no matter how many coffees?

Even if you feel you can ¿hold¿ your caffeine well, there are good reasons to limit it Even if you feel you can ¿hold¿ your caffeine well, there are good reasons to limit it

Even if you feel you can ‘hold’ your caffeine well, there are good reasons to limit it

But as a standard cup of instant coffee contains around 100 mg (takeaway coffees may contain three times this), a mug of tea around 55 mg and even a bar of dark chocolate around 80 mg per 100 g, it can soon add up.

Indeed, while we tend to think of caffeine as being present in just tea or coffee, in its pure form it’s found in 60 different plants, from the kola nut to cacao.

Caffeine has some surprising health benefits — for example, it’s been linked to a reduced risk of some types of skin cancer (more on this later) — but it is best known, of course, as a stimulant, which kicks us awake and improves our focus.

It has this effect because it blocks the action of a chemical called adenosine, which is naturally produced in the body, mainly in the liver.

Adenosine binds to receptors that are found on cells around our bodies — including nerve cells in the brain, where they play a part in our sleep/wake cycle.

Normally, our levels of adenosine rise during the day and it binds to these receptors. As a result, it slows down nerve cell activity, making us feel drowsy and tired.

But caffeine, which chemically is similar to adenosine, sticks to these receptors, too. This blocks the path of the sedating adenosine in the brain, with the result being that we feel perky and alert.

While that can be helpful in the morning, it’s one reason to avoid caffeine later in the day (I personally don’t have any after noon). But you can make the most of the stimulating effect by having your caffeine an hour before you need a mental — or physical — boost.

Caffeine is rapidly absorbed in the gut and levels peak after about an hour and steadily fall over the next five hours on average.

You can use that ‘high performance’ window to do work that requires extra brain power or to make a workout easier to bear.

A review published last year in the journal Nutrients found that caffeine increased the stamina of runners and improved their times.

But having shot after shot of caffeine won’t make you feel more alert nor run faster; research suggests a second coffee only perks you up if you have it eight hours after your first.

In one study, 49 habitual caffeine drinkers were given coffee or a placebo drink at varying times in the day — and asked to repeat mental tasks at 9am, 11am, 1pm and 5pm.

Did you know? 

Smells can act on the brain like a drug, by activating nerves in the nose that send signals to parts of the brain responsible for functions including heart rate, memory and the stress response. And research has shown that peppermint oil (try fresh peppermint tea) can help increase mental focus.

Results showed the first coffee of the day (after eight hours’ abstinence or more) improved cognition, as did a coffee at 5pm (after an eight-hour gap from the first) — but those in between had no effect, reported the journal Psychopharmacology in 2005.

This may be because caffeine gets broken down in the liver, and when you consume anything above 100 mg, this process slows down.

There are other short-term perks to caffeine. For example, it increases thermogenesis — the rate at which you burn calories to generate heat — thanks to the resulting increase in hormones such as epinephrine, which encourage fat-burning.

These effects don’t last that long — a few hours at best — but it is enough to make a difference.

A study in the journal Obesity in 2007 found that having 300 mg of caffeine led to the burning of around an extra 100 calories across the day. In theory, this would mean 300 mg of caffeine daily could keep off close to 5 kg (around 11 lb) of weight a year. But the reality is less impressive because your body adapts to the thermogenesis effects of caffeine over time.

This is why ‘metabolism-boosting’ pills that are loaded with caffeine don’t lead to weight loss in the long term.

One of the more unusual things about caffeine is its association with a reduced risk of skin cancer. Studies have found that caffeine drinkers have lower rates of basal cell carcinoma (the most common of all skin cancers) and malignant melanoma (the more deadly form).

A 2012 study in the journal Cancer Research found that those who consumed more than three cups of coffee per day had the lowest risk of basal cell carcinoma compared to those who had coffee only occasionally.

We suspect it’s the caffeine and not other components at work, as a review in the journal PLOS One in 2016 found that people who drank coffee had a lower risk of melanoma, but those who stuck to decaf didn’t.

Separate research has identified a possible mechanism: caffeine helps our bodies identify and dispose of damaged skin cells, reducing the cancer threat.

But while caffeine can lay claim to some impressive benefits, there are downsides. One that will surprise anyone who swears they need a caffeine fix to calm them down, is that it increases your stress levels. That’s because caffeine raises levels of cortisol, a key stress hormone, which increases heart rate and blood pressure.

A landmark study from the 1990s involving 25 men who were given a caffeinated drink or a placebo before a stressful task found that the caffeine group’s cortisol levels were double the levels of those given a placebo.

My suggestion is if you have an interview or other stressful event ahead, it is probably not a great day to have multiple coffees.

Caffeine is also a gut stimulant — it encourages the production of the hormone gastrin, which stimulates the muscle in the final part of the colon. If you have a sensitive gut, this can lead to diarrhoea and abdominal pain.

It can also relax the valve at the bottom of the oesophagus, which stops stomach contents coming back up. So if you have acid reflux, stick to half the 400 mg daily limit.

I would not want to do away with my morning coffee, but I stick to one — and I have started having my dark chocolate treat after lunch rather than before bed.

TRY THIS: Frothy cashew latte

Forget faffing about with soaking and straining, this nutty latte uses whole cashews, saving you time and giving you an extra hit of prebiotic fibre to nourish your gut microbes, on top of those beneficial compounds in coffee. It’s deliciously creamy, too.

Serves 1

  • 250 ml hot coffee, made to your strength preference
  • 30 g roasted cashew nuts
  • 1 Medjool date

Place all the ingredients in a high-powered blender and blitz for one minute, or until smooth. Taste and adjust flavours to your preference.

On top of those beneficial compounds in coffee, it¿s deliciously creamy, too On top of those beneficial compounds in coffee, it¿s deliciously creamy, too

On top of those beneficial compounds in coffee, it’s deliciously creamy, too

Forget faffing about with soaking and straining, this nutty latte uses whole cashews Forget faffing about with soaking and straining, this nutty latte uses whole cashews

Forget faffing about with soaking and straining, this nutty latte uses whole cashews

Tip: If you’re feeling indulgent, use salted roasted cashews for a flavour explosion. While they contain a little added salt, in the grand scheme of a whole-food, plant-loaded diet that’s rather negligible.

ASK Megan

I am 57 and over the years of perimenopause — and now menopause — I’ve developed a large belly. This may be genetic, as I recall my gran being stockily built, but I’d like to know what sort of diet might shift it. I don’t eat sweet things and I only have a couple of glasses of wine at weekends. However, I do love wholemeal bread and eat quite a bit of pasta.

Tina Sims, by email.

Abdominal weight gain during perimenopause and menopause is very common — a 2021 study in the Journal of Clinical Endocrinology and Metabolism found that compared to pre-menopause, women’s weight gain around the middle was greater during the menopause.

This change in fat distribution is thought to be down to a combination of factors, such as hormonal changes and reduced physical activity, commonly attributed to menopause-related symptoms (such as fatigue) and, therefore, reduced muscle mass.

Abdominal weight gain during perimenopause and menopause is very common Abdominal weight gain during perimenopause and menopause is very common

Abdominal weight gain during perimenopause and menopause is very common

To combat these effects, maintaining muscle mass through regular exercise and spreading your protein intake across the day (which helps stimulate muscle growth) can be game-changing.

It’s also more important to minimise blood sugar spikes that tend to be more pronounced in menopause, leading to greater fatigue and food cravings (I’ll explain more about this in my next column).

A simple way to do this is by eating your carbohydrate-rich foods (such as bread and pasta) with protein, fibre or healthy fat. For example, have an egg (protein) and tomato (fibre) with your bread instead of jam, another carbohydrate.

I’d also switch your bread to wholemeal sourdough, if available, as that has been shown to have a lower impact on blood sugar levels.

Contact Megan Rossi

Email [email protected] or write to Good Health, Daily Mail, 9 Derry Street, London, W8 5HY — please include contact details. Dr Megan Rossi cannot enter into personal correspondence. Replies should be taken in a general context; always consult your GP with health worries