Does Lemon Water Break a Fast?

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Helen Foster
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If you’re trying an approach like intermittent fasting where you leave a long break between the last meal of your day and the first meal the next, you might be wondering what, if anything, you can consume in between and still get the health benefits fasting is said to provide. In this series, we’re looking at exactly that – and today, we’re asking does lemon water break a fast.

But we go a bit further in these posts than just that. As well as examining whether drinking lemon water is okay during IF, we also look at whether it’s something you actually want to be consuming first thing in the morning on an empty stomach.

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Before we start though, we need to define what is meant by breaking a fast.

We covered this quite thoroughly in the first of this series – Does MCT Oil Break a Fast – so if you want a full breakdown, then head there, but it’s important to go through at least the basics again, so, here’s the rules.

What Classes as a Fast?

In this series, we’re not talking about fasting in a religious or spiritual sense, or the type of fasting you might need to do before a medical procedure – instead, we’re talking about fasting for health reasons.

This might include what’s known as time restricted eating where you leave a break of at least 12, and up to 16 hours, between your last meal of one day and your first the next. Or alternate day fasting where you cut calories very low for a few days a week.

Slightly confusingly, both of these also get called Intermittent Fasting.

There’s a few different reasons why you might try one of these approaches.

Some people are doing it to rest their digestive system. When we take a break of about 4-5 hours between meals of snacks the digestive system starts doing a bit of a clear out through a series of muscular contractions called the Migrating Motor Complex. This is said to play a role in keeping the gut, and the bacteria that call it home, healthy.

Lack of food also stimulates a cleaning process in your cells called autophagy which it’s said may have anti-aging and other health-giving properties.

It’s also suggested that both time restricted eating and alternate day fasting help the body metabolically balancing levels of the fat storing hormone insulin.

Plus, cutting calories a few days a week, or avoiding snacks on the sofa past 7pm, might also help you lose weight as well.

PS: IF that last one is a bit of an issue for you, have a look at our guide on how to stop nibbling at night time here.

What Then Constitutes Breaking a Fast?

How long do you have to argue?

Some fasting experts say anything that isn’t water breaks a fast. Others say it’s fine so long as whatever you consume doesn’t have many calories in it.

Another school of thought says even calories are find if they don’t impact on insulin and kick you out of the fat-burning state known as ketosis.

To get a clear definition, I therefore asked nutritionist Gabrielle Newman, nutritionist at fasting specialists The Fast 800 for her definition and this is what she said …

‘Simply put, fasting is when you stop consuming anything containing calories for a period of time. Having said this, calorie restriction (consuming less calories while eating regularly throughout the day) is also a form of fasting. 

Strictly speaking, therefore anything containing calories will break a fast – however, at The Fast 800, we have found that you will still reap the benefits of fasting even with something containing a tiny amount of calories like a small splash of milk in your tea or coffee in the morning (around one tablespoon).

If you’re fasting to improve your insulin sensitivity though, then anything that causes an insulin response would class as breaking your fast whether it contains a small amount of calories or not.’

So, using this definition what does it mean about consuming lemon water while fasting?

Does Lemon Water Break a Fast?

Gabrielle says no – and in fact,. ‘Staying hydrated while fasting is crucial, so if adding a squeeze of fresh lemon juice helps you to drink a little more water, then go for it!’

If you want a bit more explanation though, read on.


The thing is, a slice of lemon squeezed into water is going to contain a negligible number of calories – one tablespoon of lemon juice contains around 4 calories – this means it won’t impact your calorie restriction goals if that’s a reason why you’re fasting.

Gut Health

So, what about the benefits of time restricted eating? Are you going to switch those off if you have a dash of lemon in your water rather than drinking it plain?

The Migrating Motor Complex is switched on by the release of a hormone called motilin – and while studies have shown you can start it moving with as few as 100 calories from the sugar fructose found in fruit, it’s unlikely the tiny amount of calories in a water with a squeeze of lemon will be enough to get things moving.

On top of this, some research has suggested that motilin doesn’t actually switch on as readily in the presence of bitter tastes – and this may also happen with sour tastes like lemon too.

So, it’s unlikely lemon water will make a huge difference to the gut-related benefits of fasting.


Because it’s sour, lemon also doesn’t trigger a rise in insulin – in fact, drinking lemon water (or a dash of apple cider vinegar in water) before a meal is actually a suggested way to try and lower the insulin spike you get after eating.

And, because it doesn’t raise insulin, lemon water also won’t kick you out of ketosis so it’s unlikely to also stop autophagy

So, to answer our original question drinking lemon water won’t ruin your fast – but, there’s now the question as to whether it’s a good idea to use it to do so…

Should You Drink Lemon Water First Thing in the Morning

There’s a few different things we need to unpick here..

The Tooth Issue

This is a big one… drinking lemon water without food can be bad news for your teeth.

I explained this before in my post on mistakes not to make during your morning routine, but I’ll go through it again here.

You see, lemon is an acidic substance, and, even though the enamel on your teeth is pretty hard, one thing that can damage it is exposure to acidic foods and drinks – and that leads to thinner, darker and more sensitive teeth.

In one UK study, people drinking hot water and lemon or fruity herbal teas twice a day were found to be at 11 times more risk of severe acid erosion than normal.

Now, some of the damage caused by the lemon was reduced if people consumed their lemon water with breakfast – but if you’re using lemon water as part of an intermittent fasting regime, you’re not going to be consuming breakfast for a while yet so damage may be more likely.

If you want to consume lemon water on an empty stomach – and protect your teeth, drink it through a straw so it doesn’t touch your teeth – and/or then wait at least an hour after drinking it to brush your teeth. Brushing when the enamel has been softened by acidic substances speeds up erosion.

The Hunger Issue

Obviously, it’s easier to extend your fast through the morning if you’re not hungry – and Gabrielle says that one problem that can occur with drinking lemon water on an empty stomach is that ‘the acidity may stir up your stomach juices and make you feel more hungry.’

‘If this makes it harder to stick to your plan, so if you want to consume lemon water, then drink it closer to when you’d like to break your fast.’

The ‘What’s the Point’ Issue!

There’s a lot of false information out there in health world about lemon water.

It is not a magic substance. It is water, with lemon in – all that changes is that it gives a tiny little bit more vitamin C (and the ability to perhaps lower spikes in glucose which I admit, is helpful and a little bit magic)


If you’re drinking lemon water because you think it’s going to have any magic detox properties, fight cellulite, re-alkalinise your system or have some miracle impact on weight loss, then unfortunately, there is absolutely no science that says that happens.

So, by all means, drink lemon water because it tastes nice or because it makes you drink more water, but forget about any kind of magic cleansing powers.

So there you have it. The advice you need if you want to drink lemon water.

At this point, you might be wondering about other ‘lemony’ substances and whether they break your fast too. So let’s just cover those before we go…

Does Lemon Tea Break a Fast?

If it’s just black or green tea with lemon added then no as it doesn’t have any calories or noticeable effect on insulin.

However, if it’s a prepared lemon tea which contains sugar, or, you add sugar, then yes it will break your fast as sugar will contain calories, raise insulin and take you out of ketosis.

Does Lemon Cordial Break a Fast?

Again, if it contains sugar, then it’s possible that it will cause insulin to rise and take you out of ketosis so, it would break your fast.

If your cordial it contains artificial sweeteners, in theory it won’t break your fast, but, when I wrote a book with UK ketosis guru Zana Morris, she said some people do actually get a small insulin rise from artificial sweeteners, so, if you want to be super cautious, stick with fresh lemon.

Does Lime Juice Break a Fast?

Just like lemon, a small squeeze of fresh lime contains too few calories to have a major impact on your fast. As for whether it works on insulin release in the same way, I can’t find any trials that have tested it either way so I couldn’t say for sure.

Just like lemon cordial, lime cordial that contains sugar will break your fast.

So, hopefully that’s all your questions about whether you can drink lemon juice when fasting, but if there is anything else you’d like to know, or another food you’d like me to investigate, drop a note in the comments.

Who is The Wellness Nerd?

My name is Helen Foster, and I’m a health journalist and wellness author. Publications I’ve written for include Women’s Health, Reader’s Digest, Body and Soul, Good Health at the Daily Mail, and more. I have also written 16 books on health and nutrition.

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