The health effects of sugar are summed up by South Park’s Mr. Mackey:

Sugar’s bad, m’kay?

It increases your levels of insulin, hunger, and makes you fat.  Not good at all.

However, the general word on artificial sweeteners is more ambiguous.  They’ve been approved by almost all regulatory health agencies for years and are heavily tested for safety. But you always see stuff circulating on the internet about how saccharin causes cancer or aspartame promotes neural disorders and other creepy stuff.

So is there any bite to the bark?  Are we all helpless neophytes ignorantly sucking on the teet of Big Ag and the FDA?

By and large no.  Artificial sweeteners are safe and definitely better than using sugar.  They’re not particularly healthful, and can be irritants to a very small minority of people,  but are definitely harmless for the vast majority. If you look hard it’s very difficult to find a piece on the dangers of artificial sweeteners that isn’t poorly written or from a dubious source.  (And no, the DailyMail is not reputable).

For a very good piece by a source that is reputable I’d recommend this very informative article by the American Cancer Society.

I myself was a bit surprised by this, since I always assumed something so purely synthetic must be detrimental to human health, but in hindsight I suffered from the fallacy of mood affiliation.  A bias very present in health food writers.

There are a few caveats worth mentioning with regularly consuming artificial sweeteners, and they’re not a complete free lunch, but I’ll get to those in a bit.

But first, let’s start with the basics.

What They Are, How They’re Made

In the US there are five legal artificial sweeteners: aspartame, sucralose, saccharin, neotame, and acesulfame K.

Aspartame is the most popular, followed by sucralose, then saccharin.

Here’s a brief synopsis of how they work:

• Aspartame: the amino acids aspartic acid and phenylalanine linked together.  Popular in diet sodas.  Branded as Equal and NutraSweet.
• Sucralose.   A sucrose molecule with chlorine atoms attached.  Branded as Splenda.  Popular with baked goods since it’s not temperature sensitive.
• Saccharin.  Synthetically derived molecule that stores well but tastes bitter to some people.  Often mixed with aspartame since it doesn’t store well.  Branded as Sweet n’ Low.  
• Acesulfame K.  Similar to saccharin, made by NutraSweet.
• Neotame: Similar to aspartame, but 3-5 times as sweet.  Most recently approved.

Aspartame, sucralose, and saccharin are the most studied and I’m going to refer to them specifically and not Acesulfame K and Neotame since I’m less familiar with their mechanics.  But from what I understand the issues are fairly similar for all five.

Collectively sucralose, saccharin, and aspartame are some of the most extensively studied compounds on the planet.  Despite occasional rumours about links to cancer and metabolic diseases, nothing reputable has verified these claims.

On the other hand, every regulatory agency in every developed country has deemed them as safe, and the maximum amount that’s allowed to be put into foods is 100 times less than the threshold for what might be considered harmful.

You’d have to consistently drink more than 21 cans per day to approach a level that’d be deemed  “dangerous.”

The Good and Bad

Here are the good parts about artificial sweeteners:

• They don’t have calories
• They don’t cause your body to produce insulin and put your body in “fat-storing” mode the same way glucose and fructose do
• People who substitute sugar for artificial sweeteners usually end up consuming less calories and are more likely to lose weight
• Contrary to false beliefs, they don’t seem to promote any long-term health problems, unless you have a genetic disorder that prevents you from metabolizing phenylalanine (for aspartame).  This is at least true compared to sugar.

So that’s all pretty good, right?  Yep.

So why all the fear?!

Among the complaints about artificial sweeteners it’s important to separate the bogus from non-bogus.

Here’s how I’d classify them:

The Bogus:

• They’re linked to cancer. This was especially true of aspartame, but the media attention spawned from a handful of studies from one research group in Italy that were discredited later on.  Everything else since then suggests it’s benign.  (After all, it is just two amino acids linked together, nothing more).
• They’re linked to behavioral disorders.  The idea here was that artificial sweeteners may be “excitatory molecules” that could negatively effect neural synapses if consumed early in life that might affect brain development in young children.  However, it’s been shown that the compounds in artificial sweeteners either pass through your intestine entirely or are digested completely and thus don’t “swim upstream” in your body and wreak havoc.  Some people might be exceptions to this rule.
• They cause obesity.  This claim mostly comes from some epidemiology studies that show a correlation between diet soda use and weight gain over time.  This is a valid point, but the mechanistic analysis of how these sweeteners work in your body suggests that it’s not the soda itself that’s causing the weight gain.  And there are lots of others showing the exact opposite.  Here you have one type of study (epidemiology) that contradicts other types of studies (animal experiments, human clinical trials, etc),  but epidemiology studies are notorious for their inability to prove causality.

If Aspartame and Splenda Are so Safe Then What’s the Problem?

So where does the trouble actually lie?

Mostly from the problems with sweetness itself.

They come from two directions:

1).  The sweetness sensation activates an endocrine response regardless of the nutritive value of whatever’s providing the taste.

2).  Sweet sensations activate pleasure systems in your brain and foment food cravings and hunger regardless of their nutrition.

Practically all living creatures are primed to desire sweet food.  But when it comes to sugar, how much of its problems are from its structural composition and how much of it from the taste sensation it elicits?

It’s mostly due to its composition, but not entirely.

Glucose is the lifeblood of all living things, and therefore many of your body’s metabolic switches are turned on and off by changes in the way it’s oxidized.  This accounts for most of the physiological damage from eating too much sugar.

However, the sensation of sweetness elicits certain physiological responses regardless of where it’s coming from.  There are two main taste receptors for the sweet sensation, named T1R2 and T1R3.  When they’re activated they up regulate enzymes that stimulate the dopamine system in the brain, which is your body’s primary sensor for pleasure.  The pleasure button gets turned on from sweetness regardless of its source.

A part of hunger is pavlovian, so it’s likely that consistently eating low calorie sweeteners like aspartame can cause your brain to trigger pangs of hunger and trigger food addictions similar to sugar-rich foods.  However, it doesn’t do this anymore than caloric sweeteners, and probably does it a lot less since the presence of glucose itself plays a role in activating/de-activating pleasure signals in the brain.  And you’ll still be eating less calories.

But the effect is still there.

When it comes to your body’s hormonal response to artificial sweeteners things are also a little murky.  Artificial sweeteners do not cause insulin spikes and the cascade of hormonal switches that come along with it.  That’s a big deal.

However, the taste receptors for sweetness in your mouth are also located in your gut, and their activation can cause your body to secrete two chemicals called GLP-1 and GIP, which make your body want to eat more.

It’s been shown that in animals artificial sweeteners cause the body to secrete these two chemicals, which can lead to more eating and changed glucose regulation.   But these same types of studies do not create the same result when performed on humans.  In humans it doesn’t have an effect on any of that stuff.

So far at least, in humans artificial sweeteners don’t cause a hormonal response in the body that’s similar to sugar….but it’s hard to know for sure.  So there’s a caveat emptor.

Definitely Not Dangerous, Not Healthy, Can Be Used in Moderation

Like I said before, many of the sensationalistic claims about the dangers of artificial sweeteners are BS.  They’re very benign and don’t pose a potential risk for much of anything.

Don’t get me wrong, I’m not saying go out and use them!  Just pointing out that they’re probably nutritionally inert.   If you’re not a strict paleo (non-primal) or vegan (some animal by-products used in manufacturing) then you’d be wise to use them in place of sugar.

Pregnant women and children should use them with caution.

The safest thing is to avoid excessively sweet sensations entirely, but for the vast majority of people this is not possible or even desirable.

So use some Stevia or Splenda if you want to bake something, and don’t feel so damn guilty when you drink your Diet Coke!

References

Butchko, Harriett, et. al. “Aspartame: A Review of Safety”

URL: http://www.sciencedirect.com/science/article/pii/S0273230002915424

Tordoff, M G, et. al. “Effect of drinking soda sweetened with aspartame or high-fructose corn syrup on food intake and body weight.”

URL: http://ajcn.nutrition.org/content/51/6/963.short

Bellisle, France.  “Sweetness, Satiation, and Satiety”

URL: http://jn.nutrition.org/content/142/6/1149S.full

Fernstrom, John, et. al. “Mechanisms for Sweetness”

URL: http://jn.nutrition.org/content/142/6/1134S.full

Anderson, Harvey G, et. al. “The Use of Low-Calorie Sweeteners by Adults: Impact on Weight Management”

URL: http://jn.nutrition.org/content/142/6/1163s.full

Anton, Stephen, et. al. “Effects of stevia, aspartame, and sucrose on food intake, satiety, and postprandial glucose and insulin levels”

URL: http://www.sciencedirect.com/science/article/pii/S0195666310000826