Coke Zero, which was officially renamed Coke Zero Sugar in 2017, seems like the best of both worlds. It doesn't have sugar, carbs or calories like regular Coke, and the manufacturer claims that it also tastes more like the original than the company's first diet soda substitute, Diet Coke.
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But there's a reason for the old adage: If it seems too good to be true, it probably is. Like other diet sodas, Coke Zero Sugar may taste good, but several of its ingredients come with potential problems, like weight gain, imbalances in gut bacteria and decreased bone mineral density. It's not just that though. In addition to unhealthy ingredients, it lacks health-promoting ingredients.
What Is Coke Zero?
Coke Zero Sugar is a no-calorie soda option that's also free of carbohydrates, sugar and other nutrients, except for 40 milligrams of sodium and 2 percent of your daily potassium (a negligible amount that comes from potassium benzoate and potassium citrate, a preservative and buffering agent, respectively).
Coke Zero Sugar contains a total of nine ingredients:
- Carbonated water
- Caramel color
- Phosphoric acid
- Potassium benzoate
- Natural flavors
- Potassium citrate
- Acesulfame potassium
Like all ingredient lists, the ingredients in Coke Zero Sugar are listed in order of descending volume. In other words, carbonated water makes up the highest percentage of the drink, whereas caffeine contributes the lowest. Of these nine ingredients, at least three have been shown to cause negative health effects such as weight gain and kidney problems.
Health Risks of Artificial Sweeteners
Coke Zero Sugar contains two artificial sweeteners: aspartame and acesulfame potassium, or acesulfame K. Although these sweeteners are approved for use by the Food and Drug Administration and categorized as generally recognized as safe (GRAS), they may not be as desirable as alternatives to regular sugar as one would hope.
A review published in Nutrition Reviews in 2017 noted that even when consumed within recommended safe levels, aspartame can cause oxidative stress, disrupt the balance of antioxidants in the body, damage cell membranes and lead to widespread chronic inflammation.
The Science Around Artificial Sweeteners
Another study published in the Iranian Journal of Kidney Diseases in 2017 added that consumption of aspartame is linked to weight gain and obesity, metabolic syndrome, imbalances in healthy gut bacteria and possible damage to tissues in the kidneys (although there's not enough research to make definitive statements about this). It's not just Coke Zero that contains aspartame, but Diet Coke and other diet sodas as well.
Researchers also looked specifically at acesulfame potassium and published their findings in the journal PLoS One in 2017. The takeaway messages were that regular consumption of the artificial sweetener can cause weight gain, imbalances in healthy gut bacteria and genotoxicity, or negative cell mutations that could potentially cause cancer (although no definitive statements can be made about this, either).
Read more: The 10 Worst Chemicals in Our Food
Phenylalanine in Coke Zero
Aspartame also contains an amino acid called phenylalanine. Although most people can process phenylalanine without any negative health effects, it's a dangerous problem for people with a genetic disorder called phenylketonuria, or PKU.
Normally, the body breaks phenylalanine down into another amino acid called tyrosine. Those with phenylketonuria lack the ability to break phenylalanine down, and, as a result, the amino acid builds up in the body. If levels get too high, it can damage the brain and nervous system, potentially causing brain damage, seizures and learning disabilities.
Phenylalanine can also cause negative health effects in those who take certain medications, such as MAOIs and anti-psychotics, and those with the muscle disorder tardive dyskinesia. Those with anxiety, sleep disorders and any mental health condition should also exercise extra caution when ingesting phenylalanine because it can increase anxiety and jitteriness.
Health Risks of Phosphoric Acid
Phosphoric acid is an inorganic mineral acid that's used as a preservative in processed foods and drinks, like soda. It not only increases the shelf life of the drink, but it also gives it some of its characteristic tartness.
Although research on the effects of phosphoric acid on health is limited, a review published in the American Journal of Clinical Nutrition in September 2014 reported a connection between sodas containing phosphoric acid and a loss of bone mineral density in the hips of women.
Another study published in the Clinical Journal of the American Society of Nephrology in January 2017 reported that drinking sodas that contain phosphoric acid may increase the amount of acid in the blood, also increasing the risk for kidney disease.
What About Caramel Color?
That signature caramel-brown color of Coke Zero Sugar doesn't come without a cost either. This artificial caramel color is produced with ammonium compounds that break down and form a substance called 4-methylimidazole, or 4-MEI.
According to a report published in PLoS One in 2015, regular exposure to 4-MEI is one of the dangers of Diet Coke and can increase the risk of some types of cancer. In response to research connecting caramel color to cancer, California listed 4-MEI as a carcinogen under the Safe Drinking Water and Toxic Enforcement Act of 1986, which is more commonly called Proposition 65, or Prop 65.
However, the study also notes that the soda manufacturers, like Coca-Cola agreed to reformulate their caramel colorings so that they no longer contain 4-MEI. On its website, Coca-Cola notes that it did, indeed, reduce the levels of 4-MEI in its products but that they do still contain small amounts of the compound.
Read more: 15 Reasons to Kick Sugar
Coke Zero vs. Regular Coke
So should you opt for Coke Zero Sugar or regular Coke? The ideal answer is neither. It's not just the negative health effects of Diet Coke and other diet sodas that's an issue. Regular Coke may not have any artificial sweeteners, but it does contain high-fructose corn syrup, which comes with problems of its own. High-fructose corn syrup has been linked to:
- Metabolic syndrome
- Nonalcoholic fatty liver disease
A review published in Obesity in 2019 hypothesized that these negative health effects of regular Coke may be due to the high-fructose corn syrup and the difference in the way that fructose is metabolized by the liver. When in doubt as to which beverage to choose, water is always your best bet.
Is This an Emergency?
- Mayo Clinic: "My Favorite Diet Soda Has a Warning About Phenylalanine. Is Phenylalanine Bad for Your Health?"
- Boston Children's Hospital: "Phenylketonuria PKU"
- The Coca-Cola Company: "What Is Caramel Color? What Is Caramel Color Made Of?"
- The Coca-Cola Company: Product Facts: "Coca-Cola, Original, 12 Fl Oz"
- The Coca-Cola Company: Product Facts: "Coca-Cola Zero Sugar, Original, 12 Fl Oz"
- PLoS One: "Caramel Color in Soft Drinks and Exposure to 4-Methylimidazole: A Quantitative Risk Assessment"
- Clinical Journal of the American Society of Nephrology: "Diet Soda Consumption and Risk of Incident End Stage Renal Disease"
- The American Journal of Clinical Nutrition: "Soda Consumption and Risk of Hip Fractures in Postmenopausal Women in the Nurses’ Health Study"
- Nutrition Reviews: "Revisiting the Safety of Aspartame"
- Iranian Journal of Kidney Diseases: "Nephrotoxic Effect of Aspartame as an Artificial Sweetener: A Brief Review"
- PLoS One: "The Artificial Sweetener Acesulfame Potassium Affects the Gut Microbiome and Body Weight Gain in CD-1 Mice"
- Nutrients: "Dietary Sources of Fructose and Its Association With Fatty Liver in Mexican Young Adults"
- Obesity: "Are Liquid Sugars Different From Solid Sugar in Their Ability to Cause Metabolic Syndrome?"
- The Coca-Cola Company: "What Is Phosphoric Acid?"