For the vast majority, coffee is a morning necessity. The short-term benefits it has on cognitive function can be crucial to us when starting a busy day at work, and many may not feel like they can begin their routine until they’ve got a cup of it in front of them.

The proof of this is in its sheer popularity. The British Coffee Association states that around 55 million cups of it are consumed in the UK on a daily basis.

Whether or not coffee is good for us, and just how much of it can be detrimental to our health, is a subject which has been debated by researchers for a number of years. There is a wealth of reading material available on the supposed risks and benefits of coffee consumption, citing various studies; and as such, guidance on the subject is somewhat erratic.

In this post, we’ll attempt to provide some clarity on this question, to determine how many cups of coffee per day are too many.

How much caffeine is in a cup?

Coffee comes in a variety of forms and sizes, so just how much caffeine is in one cup depends on what your usual tipple is.

For example:

  • a mug (8 fl oz) of regular instant coffee contains roughly 100mg of caffeine
  • a grande (large) Americano at Starbucks contains 225mg
  • a medio latte at Costa is thought to contain 185mg
  • a lungo coffee from a Nespresso machine contains between 50mg and 90mg.

The figure of 400mg has been cited by some as the recommended daily safe limit for adults.

(During pregnancy, the NHS advises no more than 200mg per day. Adolescents are advised by Mayo Clinic to limit consumption to no more than 100mg per day.)

So in theory, no more than four cups of instant coffee would seem like the sensible consumption limit for most adults.

But as we’ll discuss, theories abound on the optimum number of cups within this range.

What can happen if you exceed 400mg per day?

Drinking too much caffeine can have a number of effects, including an increase in heart rate, stomach pain, dehydration, diarrhoea, feelings of restlessness and irritability, muscle shivers and anxiety; and the more someone drinks in a day, the more pronounced these effects will be.

However it is important to remember that caffeine is a drug, and different people tend to have different tolerance levels. For some, particularly those who aren’t used to drinking caffeine regularly, the above may well occur when amounts smaller than 400mg are consumed.

Repeated consumption can also lead to dependence. So someone who regularly consumes caffeine but skips their morning coffee on a particular day may find that they develop mild withdrawal symptoms. These might include lethargy, irritability, and headaches.

It is possible to overdose on caffeine. Too much can have a poisonous effect on the body, and cause serious liver and kidney damage, as well as heart problems. But to fatally overdose on caffeine from drinking coffee alone would take some doing; and it’s highly likely that the preliminary signs of over-consumption described above would serve as a sufficient warning for someone to stop.

However, items such as pure caffeine powder and caffeine tablets are highly concentrated sources of caffeine; so the capacity for over-consumption (and overdose) is much higher when using these.

How do you take it?

How healthy your regular cup of coffee is can also be affected by the amount of sugar you add.

If you take sugar in your coffee, this counts towards your daily RI total, which for adults is 90g.

But this RI, which you will see on nutrition labelling, refers to total sugars, and includes naturally occurring sugars found in food. The recommended intake of products containing added sugar (such as coffee containing sugar) is that they account for no more than five percent of daily calorie intake.

A teaspoon of sugar contains roughly four grams. So someone who takes two sugars in their coffee and drinks three cups per day is already up to a quarter of their total sugar RI and approaching their recommended limit for added sugar before they’ve even had anything to eat.

As we’ve written before, regularly consuming too much sugar can negatively impact upon the body in a variety of ways, by raising blood sugar levels, increasing blood pressure, triggering cortisol and adrenaline release, and lowering immune function.

So while it is advisable if you take sugar in your coffee to limit the number of cups you consume, it is perhaps more beneficial to reduce the amount of sugar you add in the first place.

When should you drink it?

Most of us are familiar with the fact that drinking coffee in the evening is not recommended, as it can have a disruptive influence on circadian function and lead to sleep deprivation.

It has long been believed that the optimum time frame to drink coffee was between first thing in the morning and lunchtime (so between 6am and 2pm for most). However, recent studies taking into account circadian rhythms and hormone release suggest otherwise.

The body releases cortisol in the morning, a hormone which acts as a natural stimulant, and helps us to wake up. As the days goes on, levels of this hormone fall, so that we start to feel more naturally tired.

Caffeine can interfere with the production of cortisol, and thereby reduce its effects.

Consequently, some experts now think it is more beneficial to time caffeine intake so that it effectively ‘rides the drop’ in this release; and they say that the optimum times to drink coffee are between 9:30 and midday, and again after lunch between 2pm and 5pm. The theory is that this helps to plug gaps in natural energy dips throughout the day.

Once again, however, it’s important to take into account that everyone is different. Those who work irregular hours may well find that coffee consumption at these times doesn’t suit their routine.

Can coffee prevent the development of certain conditions?

It has been suggested that coffee can be beneficial for health. Moreover, a number of studies have posited that moderate consumption (3-4 cups per day) can lower the risk of a number of medical conditions.

Moderate habitual coffee consumption has been found by a meta-analysis to be ‘inversely associated’ with increased risk for cardiovascular disease (it identified the highest inverse consumption level at 4 servings, with the potential risk increasing in line with increasing consumption above this); drinking 3-5 cups has been linked with a 20 percent reduced risk of Alzheimer’s; and one study suggested that drinking 3-4 cups of coffee per day can lower a person’s risk of developing type 2 diabetes by a quarter, when compared to less than two.

However, a study of moderate caffeine use in those with diabetes found that it increased daytime glucose levels, potentially presenting an obstacle to managing blood sugar and keeping the condition under control.

Increased caffeine consumption can also cause the body to pass urine more frequently, which means that they body excretes more calcium; which can affect bone health in the long term, and be a contributing factor in osteoporosis.

What the above serves to demonstrate is that there isn’t yet a definite consensus on what the ‘optimum’ level of consumption is, and also that this may differ depending on someone’s medical profile.

Our advice

If you’re an otherwise healthy adult, it’s generally advisable to:

  • try to stay under 400mg a day (the equivalent of 4 cups of instant)
  • not drink it after 5pm (or up to six hours before you plan to go to sleep)
  • and keep the amount of sugar you put in to a strict minimum.

And if you find that you’re developing withdrawal symptoms, such as headaches or tremors, it might be good to reduce your regular level of consumption, or take a few coffee-free days.

If you’re concerned about your coffee consumption or worried that it may be affecting your health, speak to your GP.