Our Verdict
When comparing Coca-Cola to Diet Coke, we picked the Diet Coke.
Why?
While the Diet Coke is bad, the Coca-Cola has mostly the same problems plus sugar.
The sugar in a can of Coca-Cola is 39g high-fructose corn syrup (the worst kind of sugar yet known to humanity), and of course it’s being delivered in liquid form (the most bioavailable way to get, which in this case, is bad).
To put those 39g into perspective, the daily recommended amount of sugar is 36g for men or 25g for women, according to the AHA.
The sweetener in Diet Coke is aspartame, which has had a lot of health risk accusations made against it, most of which have not stood up to scrutiny, and the main risk it does have is “it mimics sugar too well” and it can increase cravings for sweetness, and therefore higher consumption of sugars in other products. For this reason, the World Health Organization has recommended to simply reduce sugar intake without looking to artificial sweeteners to help.
Nevertheless, aspartame has been found safe (in moderate doses; the upper tolerance level would equate to more than 20 cans of diet coke per day) by food safety agencies ranging from the FDA to the EFSA, based on a large body of science.
Other problems that Diet Coke has are present in Coca-Cola too, such as its acidic nature (bad for tooth enamel) and gassy nature (messes with leptin/ghrelin balance).
Summary: the Diet Coke is relatively less unhealthy, but is still bad in numerous ways, and remains best avoided.
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