Marks Daily Apple
Serving up health and fitness insights (daily, of course) with a side of irreverence.
26 Jan

The Not So Definitive Guide to Diet Soda

Before I begin, I want to make something clear: this is not your standard definitive guide to whatever. I’d like to be able to issue a proclamation regarding diet soda that stands the test of time immemorial, but I cannot. Research is still in its infancy, and exactly what diet soda does to those who drink it – if anything – is incredibly confusing. The one thing I can say with any certainty is that, while it’s unfair to say it will kill you or give your unborn child prenatal tumors or make you impossibly obese, you’re probably better off without diet soda. It tastes weird, the list of unpronounceable ingredients is too long for my comfort level, and I’ve seen one too many unsuccessful dieters that seem to live on the stuff.

There are two things to consider when making any conclusions about diet soda’s place in a healthy diet. Do the ingredients used in diet soda pose a threat to your short-term or long-term (or that of your offspring’s) health? Is it a kind of sugary methadone, impeding healthy eating by making it harder to kick the desire for sweet things in your mouth because, well, you’re constantly putting things in your mouth that mimic sugar? Let’s dig in.

First, the ingredients. What goes into a can of your average diet soda?

Carbonated water, some sort of food coloring, and preservatives like potassium benzoate are all innocuous enough. Nothing to worry about there. You won’t see Mercola issuing dire warnings about Caramel Color No. 76 anytime soon. It’s the other stuff that interests (or worries) us: artificial sweeteners and (to a lesser extent) phosphoric acid. Let’s take a look at the two major sweeteners in popular use, aspartame and sucralose. Are they dangerous?

Aspartame gets a bad rap. High dose rat studies implicate it as a carcinogen, but in exceedingly large amounts. A can of diet soda a day probably won’t give you cancer. Would I avoid it as a pregnant mother? Yes. Would I be wary of drinking several cans a day? Yes. The basic takeaway is that while the clinical evidence of immediate danger upon normal ingestion of aspartame is lacking, inconclusive, or unclear, the vast amount of anecdotal evidence from people linking aspartame to headaches, migraines, panic attacks, and other maladies gives me great pause. I mean, the stuff tastes horrible, and that’s enough for me, but some people appear to have real health issues with aspartame. Not everyone, obviously, but some do. If aspartame appears to give you trouble, don’t let PubMed convince you that it’s harmless. It may very well be safe in the amounts we typically consume in the majority of people, but you can’t ignore your own experiences.

Also known as Splenda, sucralose is a popular sweetener that’s often called “natural” because it’s the product of selective sucrose chlorination. It’s 3.3 times sweeter than aspartame and 600 times sweeter than sucrose. It seems to have less of a disgusting aftertaste than aspartame (it’s all foul to me, though). Like aspartame, most of the studies reporting negative effects used insanely high doses of sucralose. I’m talking doses in the area of thousands of Splenda packets a day for months on end. I’m no fan, but I don’t think normal consumption of the stuff will kill you. There was a study that found normal doses (between 1.1 and 11.1 mg/kg per day; recommended maximum daily dosage is 5 mg/kg) of sucralose negatively impacted the gut flora in rats and lead to weight gain, although a later review called the study’s results into question. I’ll pass, but thanks, expert panel. There’s also the fact that sucralose is usually combined with something called acesulfame-K (potassium), another sweetener that many researchers think needs more toxicity tests. My take? Studies showing negative effects may be overstated or misguided, but why take the risk for that weird chemical aftertaste? Just avoid the stuff to be on the safe side.

And then there’s phosphoric acid. Here’s how the story supposedly goes: phosphoric acid, which soda makers use in place of pricier citric acid, leaches calcium from your bones and reduces bone mineral density. Is it true? Well, it’s become pretty clear that foods containing dietary phosphorus – like meat, dairy, and other “evil” foods – strengthen bones, rather than leach from them. But phosphorus isn’t exactly the same as phosphoric acid, which epidemiological studies have connected with loss of bone mineral density and osteoporosis. One in particular found that only colas (both diet and regular) were strongly associated with loss of bone mineral density. What do colas have that other diet sodas largely do not? Caffeine plus phosphoric acid. A more recent controlled trial found that only fizzy drinks containing caffeine resulted in increased calcium excretion; phosphoric acid content exerted no effect, either alone or in concert with caffeine. I don’t think we can implicate phosphoric acid just yet.

Okay, but remember: we’ve got to be careful when analyzing a food’s worth by singling out one of its constituent parts for good or for bad (although diet soda is by all definitions not food, it is a consumable whose stated purpose is to help dieters lose weight by avoiding sugar). Let’s judge diet soda on that. It may be technically safe to consume, but does it do its “job”? Does it help us lose weight by replacing our sugar intake with non-caloric sweetener intake and reducing cravings?

By most accounts, no. If you look at the literature, diet soda has repeatedly been shown to correlate with weight gain and increased incidence of metabolic syndrome:

One study found evidence of a linear dose-response; the more diet soda people drank, the more likely they were to be overweight or obese. As Sharon Fowler, the author of the study, puts it, “for each diet soft drink our participants drank per day, they were 65 percent more likely to become overweight during the next seven to eight years, and 41 percent more likely to become obese.”

Another study, which I covered a couple years ago, analyzed the diets of more than 9,500 men and women between the ages of 45 and 64 and found that drinking diet soda was associated with a 34% higher risk of developing metabolic syndrome – the perfect storm of high triglycerides, belly fat, insulin resistance, and obesity that’s so popular nowadays. This was an even stronger association than the one between the “high-meat, high-fat” Western diet and metabolic syndrome.

Authors of both studies speculate that diet soda drinking just extends the life of sugar cravings, rather than eliminating it. In this scenario, diet soda doesn’t regulate the desire for sugar; it increases it, and diet soda drinkers are simply replacing those empty calories with real sugar. This makes sense, and I think it’s part of it, but a couple other studies suggest that something else is going on entirely independent of caloric intake:

The dietary habits and weights of a homogenous group of middle aged women were tracked for a year. Regardless of initial weight status and inexplicable by “food consumption patterns,” users of diet soda were more likely than nonusers to gain weight. They didn’t eat markedly different from non-soda drinkers and yet they got fatter. It continues…

A more recent study broke rats up into two groups. The first received ad libitum oral doses of water sweetened with the maximum Acceptable Daily Intake (ADI) of saccharin, aspartame, cyclamate, and acesulfame-K (the same formulae used in commercial sweeteners), while the second group received plain water. Both were given ad libitum access to standard rat chow (which usually resembles the SAD: a disgusting mix of vegetable oils and sucrose). While caloric intake did not change between groups, the rats given non-caloric sweeteners experienced greater increases in bodyweight. The rats apparently weren’t driven to eat more because of confused satiety signals, and yet they still gained more weight. What gives?

Are diet soda drinkers eating more actual sweets to make up for the missing calories? Are their satiety signal hormones being altered by some chemical additive? Or is something in the diet soda actually causing weight gain independent of caloric intake?

We simply don’t know. We do know, however, that our bodies respond to everything they encounter. You lift a weight, you send a message to your body (build more muscle, make bones denser, establish neural pathways for movement!). You put food in your mouth, that elicits a response, even before the food hits your gut, as with the carbohydrate mouth rinse that increases athletic performance. It may be that introducing artificial sweeteners directly to your gut (bypassing the tongue) doesn’t affect subjective satiety or satiety hormones, but that’s not how we drink diet sodas. We taste them. With our tongues. And there is a decent amount of (mixed) evidence that certain artificial sweeteners in certain situations in certain individuals can actually elicit hormonal responses from taste alone, leading to hunger that isn’t really there and perhaps even insulin to handle dietary glucose that was never actually eaten. The details of any effect artificial sweeteners have on our hunger hormones are still being teased out, and the subject demands a dedicated post sometime in the future – so stay tuned for that.

In the end, diet sodas contain potentially harmful chemical additives and phosphoric acid that may or may not leach minerals. The majority of people who drink them to lose weight are unsuccessful, and most epidemiological evidence and some clinical evidence has linked diet soda intake to increased obesity, even irrespective of caloric intake. It may be that tasting sweet stuff without a corresponding caloric dose is throwing off our satiety signals and messing with our normal hormonal response to food, or perhaps relying on fake sugar just makes it harder to give up the real stuff.

Of course, whether they have a place in your diet is up to you. Maybe you’ll buck the trend and lose more weight and experience greater relief from sugar cravings with diet soda. Maybe you have one every few days and no more. If you’re a dedicated diet soda addict, maybe experiment with slowly eliminating it from your diet. Drink a bit less than usual and see how you feel. Try to save your 80/20 allowance for something a bit more fun, like maybe a high quality full-fat ice cream or a hunk of super dark chocolate (which actually has some nutritional merit, like good dairy fat). I’m gonna say that ideally you ditch them altogether, mostly because they seem to reinforce bad habits in most people and because the long term effects aren’t fully known.

Whatever you do, don’t start a diet soda habit after reading this post!

Comments? Concerns? Give me your diet soda stories. I want to hear about the aspartame headaches, the effect Splenda has on your satiety, and anything you can think of. Don’t hold back!

You want comments? We got comments:

Imagine you’re George Clooney. Take a moment to admire your grooming and wit. Okay, now imagine someone walks up to you and asks, “What’s your name?” You say, “I’m George Clooney.” Or maybe you say, “I’m the Clooninator!” You don’t say “I’m George of George Clooney Sells Movies Blog” and you certainly don’t say, “I’m Clooney Weight Loss Plan”. So while spam is technically meat, it ain’t anywhere near Primal. Please nickname yourself something your friends would call you.

  1. I don’t buy any of this stuff…if it really tasted so bad why would so many people love and drink diet coke??

    There is no evidence that only dieters use diet soda.

    I have a can or two of diet coke a day, and don’t plan to apologize for it. I usually drink it with a big portion of ice so it’s diluted. It provides the same hydration as water – why wouldn’t it? The main ingredient in soda, diet or not, is water.

    Honey, molasses, or whatever else WILL cause an insulin response in the body and does contain calories. I’ll stick to my diet drink any day…

    SkepticScientist wrote on August 23rd, 2011
  2. Sodas are highly acidic, regardless of sweetener. has best test strips and pH (acidic versus alkaline) info. is also a tremendous resource for “food as medicine”. His acronym GOMBS for greens, onions, mushrooms, beans/berries and seeds/nuts inspires my recent soup efforts (plus garlic, peppers, celery, carrots, whatever veggies available). Amy’s low sodium veggie lentil is a great starter. Enjoy soup and websites. pH into the alkaline zone and Fuhrman’s micronutrients and phytochemicals emphasis is a likely formula for a healthy and long life!

    Roe wrote on November 26th, 2011
  3. Aside from the chemicals, its worth noting that these soda drinks ROT YOUR TEETH faster than anything I know. I was warned about it by a dentist when I was a teenager and to this day am grateful for his advice! The acids in diet sodas are just as damaging as the sugars in sweetened sodas apparently. Fruit juices are also up there as teeth rotters, not as bad as soda drinks, but woth noting that the alkaline content of your saliva can deal with most natural foods but the acid wash of a fruit juice or worse – a soda drink – is not so good for your gnashers.

    Owen wrote on December 2nd, 2011
  4. I found this blog very interesting.

    A year ago, I moved, and we had a second fridge that I stocked with diet soda. Before moving, I probably drank a couple of cans per week. After moving, I started drinking it like crazy – – 3 cans per day was not uncommon.

    Oddly, I gained 12 lbs in a year WHILE training for a marathon.

    I don’t know if I really slacked on my eating habits, but I don’t think I changed THAT much. I feel as though maybe the diet soda had something to do with the weight gain.

    I stopped cold turkey and had 3 days of migraines (even though not all the diet soda was caffeinated). I’m moving toward a low carb lifestyle (just found your site and am perusing it with enthusiasm).

    I feel better, but I am not losing weight quickly. However, I have hope that maybe I can at least drop the 12 lbs I gained over the course of the year . . .

    Anita wrote on December 13th, 2011
  5. I waited tables for years and drank Coke from the fountain during my entire shift. I remember one day it just hit me that, almost without exception, the people who ordered full sugar soft drinks were obese or very young. People who drank diet soda never looked healthy (overweight or otherwise unhealthy looking). The people who were noticeably attractive and fit looking drank water or unsweetened tea. I figured that was enough of a study for me. Quit then. For about a year I would drink a soda or diet soda occasionally. Now the thought of it is completely unappealing. Eliminate don’t limit!

    NewButNotGreen wrote on January 29th, 2012
  6. I’ll be one to buck the trend, so to speak, and go “pro-diet soda” – but first let me explain why.

    I was a HUGE regular soda drinker and it’s caused me to be skinny fat for a long time. I’m am/was a sugar addict in general, until recently I decided to cut it out as much as possible and follow a more primal diet. Since soda was such a big habit, I know from past experience I couldn’t just cut it out completely, because then I’d feel too deprived, and revert back to bad eat habits across the board. It’s as much a mental thing as it is a physical thing. So diet soda is the one thing I allow myself daily for now (cut out all refined carbs, sweets, and other junk). I literally drink over a liter day, but I’ve been dedicated with the gym and the rest of my eating habits. In just about 6 weeks, I’ve dropped 12 lbs (from 172 to 160) and have a noticeable decrease in belly fat (though not totally gone). As I mentioned, I am skinny fat, so I’m not visibly overweight…so 12 lbs is A LOT for me. I still think another 10 is in order to get lean, but I feel like I’m on my way…and if I get there, it will be the first time since I was like 10 years old that i’ll have a truly flat stomach (im in my 30’s now). I know other people experience other side effects like stomach aches and such, but maybe just because I’ve been a big soda drinker since I was a kid, it doesn’t bother me?

    I realize diet soda in all odds is bad for you with all the chemicals, but this is helping me transition to avoid sweet drinks. Compared to my previous diet (loaded with sugar and processed food), this is an improvement. Im slowly starting to swap seltzer and water in as substitutes…so for every one glass of diet soda I have, I make the next glass water or seltzer to try and dwindle down the numbers (I drink a lot of liquid throughout the day). I eventually want to phase it out completely, but I know myself, and know that cold turkey doesn’t work for me long term.

    Everyone is different, and like Mark said – if you aren’t drinking it already, I don’t recommend starting! Soda is my cigarettes…I was hooked at a young age and I’ve been trying to escape for years.

    Chris wrote on February 2nd, 2012
    • Also – my main point was to show that in my case, diet soda doesn’t appear to be what makes you fat. I’m drinking it in quite large quantities (I honestly drank close to 2 liters today), and if you added up the calories I’d be consuming if it was regular soda, I’d be GAINING weight instead of losing it. I’m convinced that those studies that show people gaining weight is because the rest of their diet is crap, and they are victims of the “Big Mac with a diet coke” syndrome.

      Again – not advocating it as being healthy, but i don’t think it causes obesity either.

      Chris wrote on February 2nd, 2012
  7. So I bought some cordial called ‘The Naturdal Cordial Company’ apple raspberry flavour, when I was trying to be healthy, before I discovered Primal.. And I haven’t touched it since. My husband however, has been going through the few sugary things we have left in the house he has recently finished the bottle of normal cordial and then yesterday he had a strawberry milk made from some milkshake syrup which I’m sure must be packed with sugar. (a big drink of milk usually makes him sick so he steers clear) He can’t seem to kick sugar! I just picked up my bottle of ‘healthy’ cordial and went straight to the amount of carbs and sugar listed.. Carbs 2.2 per 100g, Sugar 1.2 per 100 grams, Erythritol 1.0 per 100g.. It’s sweetened with stevia!

    So that’s good right? I mean I can safely have (and feed my husband) a nice sweet drink of cordial without feeling guilty or ruining my eating? It’s basically just fruitness, water and a bit of stevia..??

    Kate wrote on February 27th, 2012
  8. I was a big Coke Zero fan, especially the vanilla variety. Then I watched ‘Sweet Misery’ (available on the net on vimeo, I think) … I don’t drink it any more. The aspartame business is nasty from the process of getting it approved to the massive list of side-effects. I actually feel guilty for giving my 7yo daughter a sip occasionally …

    Vim Fuego wrote on April 30th, 2012
  9. So I’ve been reading everyone’s comments on the soda issue, have noticed several people mention Soda Stream, which we own and use (a lot!). One of my friends was saying that anything carbonated with CO2 had carbonic acid in it and would cause loss of bone mass and tooth enamel degeneration. I can’t find anything in the MDA archives (maybe I’m just not trying the right search criteria) regarding this.
    So-we’re really new to PB. Very happy so far-I got my husband and son to agree to try this and today is our one week anniversary. We’ve lost 18 pounds as family! (Hubby-11, me 5 and our son, not really overweight yet with a little pot belly, 2.)
    We’re eating delicious home cooked meals, saving a ton on restaurant bills. So-does anyone know if my friend is right? I would hate to be trying so hard to be healthy and unknowingly doing something that could sabotage our health down the road. My son hates (yay!) anything fizzy, drank maybe one glass of juice every couple weeks, so his fluid intake has remained the same- milk and water. I was never a really big soda drinker, my fav remains iced tea with lots of lemon and some sweet-n-low. I haven’t had that, switched to Truvia for both ice tea and coffee. Haven’t noticed any sugar cravings associated with that, though I’m guessing the erythritol portion is probably a sugar alcohol. We do drink plain water, but the fizzy stuff (plain or with lemon) is very nice with meals.
    So-soda water OK or not? Any comments/knowledge would be greatly appreciated by a couple of newbies. Thanks.

    BJML wrote on May 20th, 2012
  10. I just wonder if there is an insulin response or not??????
    I’ve been trying to adapt to this diet by slowly switching over for the past week now, but really enjoy a dt dew in the morning or at lunch. Despite the other possible health affects, I would really love to continue doing so if it doesn’t affect insulin.

    Mike wrote on July 22nd, 2012
  11. The migraine response to aspartame seems to be genetic. My mother-in-law, wife and daughter all suffer migraines when they consume aspartame and only when they consume aspartame. Those of us with Y chromosomes do not seem to be afflicted with these symptoms, but statistically, women are more prone to migraines in general (my doctor has a poster about migraine vs. cluster headaches). As I am well above my ideal weight, I’m going to begin elimination of soda (and energy drinks) from my routine, but it’s going to be a long road, as my office trash can is full of energy drink cans and I have a 32oz fountain drink on my desk at the moment.

    John Harris wrote on August 16th, 2012
  12. If I give up diet coke and substitute with water, I’m inclined to try sparkling water. Are there salt issues with that?

    ijon wrote on September 6th, 2012
  13. While on the path to learning how to take care of my mind, spirit and body I have learned that I need to start trusting my intuition and I have this intuition that drinking Diet Coke is somehow messing with me in a way that prevents me from reaching my body fat goals. I’m a data driven guy though and finding the data that definitively validates my intuition is next to impossible. The only option I can see left is to stop the Diet Coke all together and see what happens :)

    MikeDice wrote on January 21st, 2013
  14. Even with carbohydrate intake of < 25 g per day, the addition of one diet soda per day COMPLETELY stalled what had been very steady weight loss and started me on the path to eating badly again.

    I also did some self-experimentation to discover it is a major trigger for migraine and anxiety attacks. It's not the caffeine alone, b/c coffee does not have the same effect.

    I do love soda, though, so I make it a weekly treat. I have one soda made with real cane sugar on the weekend. And I walk the mile to the healthy grocery store to buy it, and back, so the exercise burns a lot of the sugar.

    In the summer here in Mississippi it is very hot. I make sun every couple days – steeped outside in an old 3 qt Ball mason jar pail for about 3 hours. I use a mix of green, black, and peppermint tea. The peppermint makes it even more refreshing.

    I "sweeten" with just enough honey to not make it sweet, but just cut the bitterness. Add lemon, and it's incredibly cooling on a summer day.

    Kristen wrote on March 10th, 2013
  15. I’m a huge Diet Pepsi fan and I drink a lot of it every single day. I’ve read countless stories about the harmful affects of its ingredients and horror stories from others similarly addicted. But nothing I’ve read (or seen) so far has made me cut it from my food choices.

    I do admit though that reading through all that material I think I probably SHOULD cut it out but just don’t want to. Occasionally, I have gone cold-turkey and drank only cold water with a splash of lime or lemon. Last time I did that it took about 10 days before I was back to the Diet Pepsi. I don’t like the taste of the regular Pepsi or any other soft drink. If DP isn’t available then it’s water for me.

    I started with Primal Blueprint at the beginning of Oct. (2013) and have been losing 1-2 lbs. a week, while continuing with my beloved Diet Pepsi consumption as usual.

    I don’t gamble, or drink any alcohol, or smoke – so this is my one vice and I’m keeping it!

    Darlene, San Francisco, CA wrote on November 6th, 2013
  16. There’s that word “associated with”. Does it ever occur to people that the whole reason they are drinking diet sodas is precisely because they are overweight. There’s no reason to drink them if you don’t have problems with your weight. So of course, epidemiological studies will show that the people who gain weight are drinking them. Come on people, Think!

    Pascal wrote on May 25th, 2016

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