Is Diet Coke Bad For You?


It is sure to get jimmies rustled, get you unfollowed on Facebook and get gym leggings in a twist but is diet coke bad for you?

Seriously, we have been accused of being sponsored by Coca Cola before by someone who didn’t like it when we said that it’s not that bad for you. There’s the cat out of the bag already.

Why something so insignificant as a can of juice can command such hatred and why it’s the cause of many a hot debate is….well, quite frankly, bizarre.

Anyway, let’s get into it – is diet coke bad for you?

Listen to some and they’ll have you running to the hills with fear. You may have heard:

  • Diet coke causes cancer
  • It tricks your body and turns on fat-storing-mode
  • All diet drinks deplete nutrients and make you hungry
  • It’s filled with chemicals therefore it’s pretty much poison
  • Diet coke is the cause of all things evil, should be banned and how dare you, a nutritionist, say that it shouldn’t be outlawed

Now, before anyone gets even more worked-up and accuses us of saying it’s ‘healthy’ let’s get a few things straight.

There are a lot of myths surrounding the drink that are simply just a load of nonsense. This article is going to clear the confusion. What does the evidence say about diet drinks?

Also, just to clarify, before anyone drops the usual “this is sponsored by Diet Coke” no it isn’t. Pepsi Max or Diet Irn Bru are much better anyway…..

Is Diet Coke Bad For Your Health?

Probably not that bad at all.

There are no studies that indicate any long-term health risks from drinking diet soda. Diet Soda….is not harmful to health, well-being, or body composition

So far, so good for the coke zero and diet coke fans.

There are no studies that indicate any long-term health risks from drinking diet soda. Click To Tweet

What about the cancer risk?

Back in the 60’s, there was a study that linked aspartame (the sweetener in diet coke) with brain tumours but more recent evidence has proven that this isn’t the case and that there is no link between diet drinks and cancer.

A review paper in the Regulatory Toxicology and Pharmacology Journal concluded that:

…the studies provide no evidence to support an association between aspartame and cancer in any tissue…..the weight of scientific evidence confirms that, even in amounts many times what people typically consume, aspartame is safe for its intended uses as a sweetener and flavor enhancer…..

What About The Chemicals?


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My buddy said aspartame ingestion produces methanol and formaldehyde.”

Yes, that’s formaldehyde as in the stuff used to preserve dead bodies.

Whist it is true that aspartame is broken down into methanol (which is then converted into formaldehyde), as well as two amino acids, phenylalanine and aspartic acid – it is extremely unlikely to be detrimental to health.

Why? Well, the key is in the dosage.

Just because something has chemicals in it does not mean that it is harmful. Whether a chemical is natural or man-made doesn’t tell you anything about how toxic it is.

There are many naturally occurring chemicals in plants that are extremely toxic to humans in small amounts. On the other hand, there are many man-made chemicals that are totally harmless to us, even when consumed in large quantities.

Toxic fruit?

There are fruits and vegetables that everyone agrees would be classed as ‘natural foods’. However, many contain compounds that have been shown to be toxic to humans. The good news is that the dose is so small that you would never be able to eat enough of them for it to be harmful.

Just because something 'contains chemicals' doesn't mean it's automatically unhealthy. Click To Tweet

Semi-skimmed milk, for example, contains 6-9x more phenylalanine and 13x more aspartic acid than a diet coke. Tomato juice also has 4-6x more methanol than a diet coke too.

The air you breathe has chemicals in it, then you use that oxygen and that forms chemicals within you. The water you drink is a chemical and then you use it to form more chemicals; all of the carbs, protein and fat you eat are products of chemical reactions and then you use them in chemical reactions in your body.

Finally, formaldehyde is produced by our bodies every day in amounts thousands of times greater than you would ever get from aspartame. It is actually needed to make essential compounds, including your DNA. Source: Academy of Nutrition and Dietetics

Here’s another example of why dosage is key and just because something “contains chemicals” doesn’t mean it’s automatically unhealthy. Apples, cherries and apricots all contain the poison cyanine!

[RelatedToxins, Diet Cokes, Pseudoscience & Fighting The March Of Unreason]

Do you avoid them for this reason? No, because the dosage is insignificant. Ever heard of apple eaters dropping like flies with cyanide poising, no, of course you haven’t.

Anyway, back to diet coke…

Does it get the thumbs up? No so fast, your dentist won`t be a fan.

One thing to mention is that diet drinks, although sugar free, may not be great for your pearly whites.

Studies have shown that carbonated drinks aren’t great for tooth enamel, which is one reason why you may not want to go overboard with the coke zeros.

So far, according to the science, diet cokes aren’t bad for your health. But…

Is Diet Coke Bad If You’re Trying To Lose Fat?

Let’s get something straight, weight gain and weight loss is determined by calorie balance (calories in vs calories out):

A fundamental principle of nutrition and metabolism is that body weight change is associated with an imbalance between the energy content of food eaten and energy expended by the body to maintain life and to perform physical work” ~ Am J Clin Nutr

A drink that contains zero calories cannot cause you to gain weight. It’s physiologically impossible. There is no evidence that shows drinking diet drinks will result in fat gain.

A drink that contains zero calories cannot cause you to gain weight. It’s physiologically impossible. Click To Tweet

Some studies have actually shown that sweeteners may even improve weight loss and long-term control of body weight.

How can this be? Ever had a sweet tooth? Of course you have. Sometimes artificially sweetened foods, although unlikely to serve any nutritional benefit can eliminate sugar cravings.

If a zero calorie diet coke is the “go to” instead of a 300 calorie chocolate bar, it doesn’t require an expert to explain why this is going to make a difference to the waist line.

[Related: 11 Ridiculous Myths About Fat Loss]

Overweight Folks And Diet Drinks

Now some studies have shown that people who are overweight or obese drink more sugar-free drinks than people who are a healthy weight.

But is the diet coke to blame? Unlikely.

These studies have also shown that the overweight people – who were drinking the diet drinks – had a much higher calorie intake than those who didn’t.

What’s more, people who generally have poor diets may also be more likely to drink diet drinks to offset the high amount of calories consumed by making poor food choices.

Although overweight people may drink more diet drinks, the diet cokes are unlikely to be the cause of the problem. This is a classic example of why correlation does not equal causation. Here’s another example:

In America, in summer, people eat more ice cream. More people also get eaten by sharks in America, in summer..

One does not cause the other, ice cream does not cause shark attacks, just like Diet Coke doesn’t cause obesity.

Ice cream does not cause shark attacks, just like Diet Coke doesn’t cause obesity. Click To Tweet

Does Diet Coke Increase Heart Attack And Stroke Risk?

arginine pre-workout

An observational study published in February 2019 reported that people who drank diet drinks were more likely to suffer from heart attacks or a stroke.

However, because the study was observational it just looks at associations or links between the participants, rather than directly showing that diet drinks increase heart attacks or strokes. It also doesn’t actually explain why diet drinks might be linked to an increased risk. Follow?

Just like in the section above about overweight people drinking more diet coke, the folks more at risk of heart attack or stroke, due to other lifestyle factors, could be drinking more diet drinks in a bid to be healthier or manage their weight.

Lastly, the British Heart Foundation are still are happy with the safety of sweeteners and recommend them over a full sugar drinks every time.

Wait, Does Coke Trick Your Brain?

You’ve heard this one before too, haven’t you? That diet coke tricks your brain that it’s actually sugar.

The argument often centres around insulin (a hormone which plays a key role in the regulation of blood glucose levels). You’ll get folks that say that diet coke causes an insulin spike which results in weight gain.

Again, if you look at the evidence, this doesn’t happen in healthy humans or even in diabetic patients.

Diet Coke Can Clean Coins, So It Can`t Be Good!

The logic applied by some, is that if diet coke can clean coins, it can`t be good for your insides, which seems reasonable.

Other cleaning-related uses for diet coke are that it is good to clean rusted battery terminals, clean toilets and polish cars. The old favourite is that traffic police apparently carry two gallons of coke in their car boots to remove blood from the road after a car accident.

Here’s the deal.

Fizzy drinks contain carbonic acid which make them good stain removers.

Guess what? Plain old fizzy water or soda water does exactly the same thing. It isn’t anything mythical or chemical about the diet coke that makes it a good cleaner. It’s simply the carbonic acid.

Folks have been drinking fizzy water for years with no side effects and again. There is zero evidence that shows moderate consumption is detrimental.

Finally, the gastric acid in your stomach is far stronger than any acids found in fizzy juice anyway.

The Round-Up: Is Diet Coke…or Any Diet Drinks Bad For You?

Diet drinks aren’t ‘healthy’ but there isn’t really anything particularly ‘unhealthy’ about moderate consumption of them either.

If weight loss is the goal then swapping from a regular fizzy drink to a diet drink is probably going to be beneficial. If you’re a fizzy juice fiend then switching from three normal cokes to three diet cokes would cut sugar intake by around 90g. This will reduce calories by almost 400, which will likely help your waist line and you can do so knowing that the evidence shows that it’s safe to do so.

Similarly, if you’re often dehydrated and you find you can’t keep your fluids topped-up because you find water a tad dull then a slash of no-added sugar squash may make drinks more palatable and as a result, improve your hydration levels.

On the other hand, if you currently don’t drink diet coke and you’re perfectly happy with water, teas and coffees and so on then there certainly aren’t any health benefits to be had from diet drinks, you’re not missing anything.

It`s up to you what you drink but plain old water is still our favourite!

What do you think? Do you drink diet coke or do you avoid it? Let us know in the comments section below.

Is Diet Coke Bad For You & Is It Worse Than Regular Coke?

Scott is the owner and founder of Food For Fitness. He is a fat loss coach, speaker and fitness writer with a masters (MSc) degree in Applied Sports Nutrition.