Why Artificial Sweeteners Are Bad for You

By Stephen T. Sinatra, M.D., F.A.C.C., F.A.C.N., C.N.S., C.B.T.

When it comes to nutrition and heart health, there are a handful of questions that always seem to be on the tip of everyone’s tongue. The most popular is about cooking oil (another topic for another day)—but a close runner-up is about artificial sweeteners. Specifically, are artificial sweeteners bad for you?

It is an important question since many folks are looking for ways to reduce the amount of sugar they consume and to lose weight.

Believe it or not, artificial sweeteners have been around for more than 130 years—and for about 100 of them, experts have been debating their relative benefits and dangers. Industry insiders would probably claim that time alone supports their products’ safety. I disagree, though. The simple fact that studies continue to suggest artificial sweeteners may pose health risks tells me that they’re not nearly as safe as marketers would have us believe.

What, Exactly, Are Artificial Sweeteners?

I suspect one reason there’s confusion around artificial sweeteners and their dangers is that the terms “artificial sweetener” and “sugar substitute” are often used interchangeably, even though they’re not the same thing. For example, aspartame and xylitol are both sugar substitutes—but they’re quite different in terms of their creation and nutritional profile.

I consider artificial sweeteners to be synthetic, chemically processed, non-caloric sugar substitutes. There are a handful of them currently approved for use in the United States, but you’re most likely to run across these four:

  • Aspartame (Equal®, Nutrasweet®)
  • Saccharin (Sweet’N Low®, Necta Sweet®)
  • Sucralose (Splenda®)
  • Acesulfame potassium, or ace-K (Sunett®, Sweet One®)

Saccharin is the oldest of the bunch, dating back to the late 1870s; however, the use of artificial sweeteners has increased exponentially since the introduction of aspartame (early 1980s), ace-K (1988), and sucralose (1998). Today, artificial sweeteners are found in virtually all diet soft drinks, low-calorie foods, and sugar-free candy and snacks—as well as those colorful packets on restaurant tables.

Short-Term Impact: Confused Metabolism

To say these sweeteners are incredibly potent is an understatement. All of them are at least 200 times sweeter than sugar. (Sucralose is 600 times sweeter!)

Food manufacturers have taken advantage of this by substituting tiny amounts of artificial sweetener in lieu of sugar. This allows them to make products that taste sweet, but without the added calories real sugar contains.

In theory, this seems like a great way to help people reduce the amount of calories they consume. But in the body, artificial sweeteners are metabolic bait-and-switch schemes that actually have worse side effects than sugar.

Let’s use diet soda as an example. When you drink a diet soda, the sweetener activates your taste receptors just like sugar does—and that, in turn, stimulates appetite and causes your body to release a number of hormones.

One of those hormones is insulin, which is produced to remove the anticipated influx of glucose from the blood. However, because the sweetener doesn’t have any actual glucose in it, the insulin ends up removing whatever sugar is already in the blood—causing blood sugar to dip too low, and further triggering the appetite, to compensate.

The other hormones released help regulate the appetite cycle and include leptin, which lets your body know it’s consumed enough calories and is “full.” Again, though, because the sweetener doesn’t deliver any actual calories, the leptin circulates but is never sends back a message to stop. The appetite loop is effectively opened but never closed—so you continue to feel hungry.

In the end, that “low-“ or “zero-calorie” diet soda quite likely has led you to eat some chips, a cookie, or whatever else happened to be nearby. That doesn’t sound like an especially effective dieting aide, to me!

Long-Term Artificial Sweetener Side Effects

If appetite and metabolism can be disrupted each time an artificial sweetener is consumed, it’s easy to see how long-term consumption could damage health. Here are some dangers of artificial sweeteners to watch out for:


If you feel hungry, as sweeteners are prone to make you, you’re more likely to eat a little extra and gain weight, instead of losing it. And as far back as the mid-1980s, research was already suggesting this to be true—and that artificial sweeteners worsen the very problem they are marketed to solve.

One study, which followed more than 75,000 women (ages 50 to 69) for a year, found that those who consumed artificial sweeteners were more likely to gain weight, regardless of their initial weight. Another trial, which followed more than 5,000 adults for approximately nine years, also found that subjects who drank artificially sweetened beverages were more likely to gain weight—47 percent more likely. Worse, weight gain often comes in the form of harmful belly fat.  A report in the Washington Post shared data from the San Antonio Longitudinal Study of Aging (SALSA) showing that “daily and occasional diet soda drinkers gained nearly three times as much belly fat as nondrinkers, after they ruled out other factors such as age, exercise and smoking.”

Type 2 diabetes and metabolic syndrome

If artificial sweeteners can increase belly fat and weight gain, it makes sense that they also may increase risk for metabolic syndrome and type 2 diabetes. A study published in Diabetes Care confirmed this:  drinking diet soda on a daily basis was associated with a 36 percent greater relative risk of incident metabolic syndrome and a 67 percent greater relative risk of type 2 diabetes, compared with non-consumption.

Changes in gut bacteria

A 2014 study published in the journal Nature was the first to suggest that saccharin can alter gut flora, and that those changes may cause metabolic disorders. Researchers in Israel found that mice given water spiked with glucose and saccharin were more likely to develop high blood sugar than mice whose water was spiked with only glucose. They linked this change to gut flora when they were able to demonstrate that killing the rodents’ gut flora with antibiotics also reversed the blood sugar issue. Conversely, when they used fecal transplants to introduce the altered bacteria in healthy animals, they, too developed high blood sugar.

This is significant not only because it demonstrates another danger of artificial sweeteners, but also because the gut microbiome is linked with aspects of health unrelated to metabolism—including immunity and mood. Changes to the flora could have unanticipated effects beyond metabolic dysfunction.


As if potential diabetes and changes to the gut microbiome aren’t risky enough, two of the artificial sweeteners on our list—saccharin and aspartame—also have at some point been labeled as carcinogens. In the early 1970s, saccharin was found to cause bladder cancer in rats; aspartame has twice come under review for potential links to cancer, most recently in 2005.

Subsequent studies have found both substances to be safe but, frankly, I’m still skeptical. People may say I’m overreacting, and so be it. My point of view is rooted in one of the things I’m most vigilant about as a doctor—avoiding the unintended consequences of believing we can do things better than Mother Nature. This potential side effect of artificial sweeteners is one health risk that I’m just not willing to take.

Minimize the Dangers of Artificial Sweeteners With These Alternatives

The best ways to avoid the potential side effects of artificial sweeteners are by carefully reading food labels (you’ll be surprised how many include a sweetener), eating mostly whole foods, and opting for more natural alternatives when sweeteners are called for. Good options include—

  • Small amounts of local honey or maple syrup
  • Fresh juice from grapes, oranges, pears, and peaches
  • Shredded apples, coconut, raisins, or dates
  • A dash of cinnamon, cloves, or nutmeg

As far as other sugar substitutes go, stevia is one that I am okay with. It’s an herbal supplement that’s routinely used in South America, China and Japan. Look for it in health food stores.


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