Are artificial sweeteners, sugar alcohols, and regular sugar all bad? An update on effects on the gut and what it means for you

When I was diagnosed with Type I Diabetes at 14 years old, I thought artificial sweeteners were God’s gift to diabetics. I couldn’t have much sugar anymore (or at least needed to cut way down to make life easier), yet there was this miraculous way to still have sweets without the calories or blood sugar ramifications.

How delightful.

As Diet Coke became my new best friend, I got to know sugar free Red Bull and skinny vanilla lattes pretty well too. Looking back, I am sad I wasn’t aware enough of my body to actually tie it together that those were actually making me feel pretty sick.

I remember this one New Years that I spent with a girlfriend of mine in Seattle when we were 22ish. We decided not to drink that New Years and instead just stayed hopped up on sugar-free energy drinks. Pretty sure I was rocking my vegetarian lifestyle too and had tofurkey meat slices laden with soy and awful fillers and other sorts of sugar free candy…  

We woke up the next day honestly feeling just as hung over as if we had drank the night before.

We went out to coffee and were just looking at each other, confused as to why we felt so crappy. It’s not like we thought sugar-free Rockstar was GOOD for you, but surely it wasn’t comparable to alcohol, right?

Oh, Therese. You silly, naïve, 22 year old. So much learn.

To be clear, I am not saying it IS the same/worse/better than alcohol, but there is definitely a reason we felt the way we did after that night.

So, if you are dabbling in a low-carb diet or just trying to cut sugars down but going for the artificial replacements, I would like to take this opportunity to share with you some of the science behind artificial sweeteners, sugar alcohols, and “natural” non-caloric sweeteners so you can make a more educated decision when choosing food and drink.

Why do we love sugar so much?

It is no mystery that people love the sweets. Maybe you have even heard sugar is comparable to cocaine in how it affects the brain (5)? Sugar is VERY addictive. To be clear: I mean table sugar and high fructose corn syrup found in cereals, desserts, drinks, yogurts, ketchup, and a whole slew of other foods. I am concerned less with sugar in whole, natural foods, like fruit because the latter do not contain the dense amount of sugar that other packaged products do and are therefore far less stimulating and addictive.

With that said, of course it sounds great to have your diet soda without the problems sugar brings with it like excess calories, health problems, energy swings, etc.

But, is it really a better choice to grab the sugar-free option? 

I want to say straight-up that the research is a little slim on artificial sweeteners in human models, but that there is still some very compelling evidence that provides valid reasons to either stay away completely, or cut way back on your artificial sweetener intake. Let’s get some definitions down first.

What are artificial sweeteners?

Artificial sweeteners, also known as non-caloric or non-nutritive sweeteners, are compounds used to sweeten a variety of foods, medicines, gum, toothpaste, mouthwash, and other sneaky items. As the name implies, they do not provide any calories or nutrients to the body.  You may recognize a few:

  • Aspartame (Equal and NutraSweet)
  • Sucralose (Splenda)
  • Sacharin (Sweet ‘N Low, Sweet Twin, NectaSweet)
  • Acesulfame K (Sunett and Sweet One)
  • Neotame

These sweeteners are MANY times sweeter than table sugar and high-fructose corn syrup. I’m talking 600x’s (Splenda) sweeter. Dr. David Ludwig, an obesity and weight-loss specialist at Harvard-affiliated Boston Children’s Hospital (also partially behind the documentary “Fed Up”), points out “a miniscule amount produces a sweet taste comparable to that of sugar…Overstimulation of sugar receptors from frequent use of these hyper-intense sweeteners may limit tolerance for more complex tastes.”

Meaning, you won’t find less sweet foods like fruits as tasty, so foods like vegetables will be downright unpalatable. Sound familiar?

Your taste buds and your body are telling you the wrong thing, like “eat that key lime pie flavored yogurt instead of the plain Greek” because of how you train them with these overly-sweet foods (3). This is called “hyper-palatability”. We like the stimulation high fat, high salt, and high sugar provide and have an actual physiological response that encourages continued consumption. When separated, high fat isn’t necessarily THAT palatable without high salt and/or high sugar, but that high sugar is ALWAYS stimulating.  

Are Sugar Alcohols artificial sweeteners?

Sugar alcohols are a little different than other artificial sweeteners because they are partially absorbed in the gut. They are compounds found in a variety of foods, but mostly low-carb/low-sugar foods to be more appealing to folks watching their sugar intake. I find them pretty sneaky in foods like protein bars, supplements, gum, and more. Since they are partially absorbed, they have some but not all the calories and glycemic effect that regular sugar may have. Some are absorbed in the small intestine by passive diffusion and a number of them, such as isomaltose, maltitol, lactitol, and xylitol, can reach the colon (8) where they can ferment to create gas or pull water in and create diarrhea (6). This is one of the reasons some people may not handle sugar alcohols very well.

Here are a few more examples:

  • Sorbitol
  • Xylitol
  • Erythritol
  • Lactitol
  • Maltitol
  • Mannitol

The research around sugar alcohols trends toward advice of just “watching intake” since some negative reactions have been found, but overall can’t be entirely conclusive about benefits or harms. One, xylitol, has been shown to cause dysbiosis in the gut- changing the bacterial balance in an unfavorable way and another, erythritol, as actually shown to have some benefit in the gut. It breaks up biofilm and can in turn make probiotics more effective and even prevent tooth decay and candidas (6).

I generally recommend just staying away unless you are using erythritol pretty exclusively and minimally in, say, baked goods. Otherwise it’s just becoming a replacement to still stimulate your taste buds in the same fashion as sugar, continuing the cycle.

What about natural sweeteners?

There is some debate in the health world about how great natural sweeteners, like Stevia or Monk Fruit, are for you. While I think Stevia MAY be a better choice than the previous list, my thoughts on the matter are a little more complex. First, research is lacking a bit with Stevia, which always makes me a little more skeptical. Second, as discussed before, you are still choosing the SWEET option. You are still training your body and taste-buds to be over-stimulated with hyperpalatable flavors which can lead to cravings in the future.

Monk Fruit probably gets my biggest stamp of approval, but it is also not as sweet as others (part of why I like it). I have not come across research at this point that speaks negatively about it, though I highly encourage more research on YOUR end to be done until I get more information.

Artificial sweeteners and your gut

Okay, now that I have established a few definitions, lets dive into some major reasons I do not love artificial sweeteners. If you haven’t guessed already, artificial sweeteners are not good for the gut. They change the bacteria in your gut in a way that has a profound role in changing metabolism, especially that of sugar (2, 4, 7). This means that effects of insulin resistance, weight gain, impaired use of glucose, can compound and lead to some serious conditions.

Additionally, “researchers from Ben-Gurion University of the Negev in Israel and Nanyang Technological University in Singapore tested the toxicity of aspartame, sucralose, saccharine, neotame, advantame, and acesulfame potassium-k. They observed that when exposed to only 1 milligram per milliliter of the artificial sweeteners, the bacteria found in the digestive system became toxic”. (7) Not good.

What else does the research say?

As I mentioned before, most of the research has been done on animal models, which makes concluding evidence hard to apply to humans. However, there have been a decent amount of studies done on both animals and humans that challenge the belief that artificial sweeteners are a better option over regular sugar.

Research notes:

  • No evidence that sweeteners like aspartame and sucralose help people manage their weight (2)
  • Sweetener consumption may sharpen your sweet tooth, prompting you to eat more sugary foods, or make you feel virtuous and overcompensate later (2)
  • The sweet taste paired with no calories may confuse the body and change how it handles real sugar-shown in lab animals (2)
  • Research participants who drank more than 21 diet drinks per week were twice as likely to become overweight or obese as people who didn’t drink diet soda (3)
  • Daily consumption of diet drinks was associated with a 36% greater risk for metabolic syndrome and a 67% increased risk for type 2 diabetes (3)
  • Can lead to glucose intolerance (4)
  • Positive correlation between sweetener consumption and clinical parameters related to metabolic syndrome: weight, waist-to-hip ratio, fasting blood glucose, hemoglobin A1c, glucose tolerance test, and ALT (4)

With all of that said, there are definitely limitations to the studies, and more research needs to be done. I do like to err on the side of caution when consuming modern, industrial foods. As Chris Kresser has said before, the approach to these foods should be “guilty until proven innocent”. You are likely part of a population-wide experiment with these sugar substitutes right now, just like we were part of the experiment of the high omega-6 vegetable oils (4). We know that didn’t go over well…

I don’t think that having a diet or sugar-free drink here or there is going to kill you. I also don’t think having a regular sweet yogurt or soda will kill you. I am mostly concerned with how the intake affects your sweet cravings, and the effect on your gut microbiome. Those things can be the root of all evil when it comes to holding you back from reaching your optimal health. Please consider looking at all labels before choosing a product, if not to just create more awareness. After all, did you know sweeteners can hide in:

  1. Toothpaste and mouthwash
  2. Supplements
  3. Children’s chewable vitamins
  4. Cough syrup and liquid medicines
  5. Chewing gum
  6. No-calorie waters and drinks
  7. Alcoholic beverages
  8. Salad dressings
  9. Frozen yogurt and other frozen deserts
  10. Candies
  11. Baked goods
  12. Yogurt
  13. Breakfast cereals
  14. Processed snack foods
  15. “Lite” or diet fruit juices and beverages
  16. Prepared meats
  17. Nicotine gum

Yikes! Check the labels, people. If you really want the sweet stuff, indulge in moderation with natural sweeteners like honey or maple syrup, or if you’re watching blood sugars, erythritol, stevia, and monk fruit can be used.

Therese Martinez, MS, RD, CPT


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