Mother Talkers

Diet drinks and metabolic syndrome

by lyn

Thu Feb 07, 2008 at 01:42:18 PM PDT

A new study came out linking diet soft drinks to the development of metabolic syndrome, a set of symptoms that indicates a high risk for cardiovascular disease and diabetes.  This is a prospective study that assessed the dietary intake of over 9000 metabolically normal middle-aged participants, then followed them for 9 years watching for the development of metabolic syndrome.

Unsurprisingly, high intakes of meat and fried food were positively correlated with metabolic syndrome while dairy appeared to be weakly protective.  But the strong correlation with diet soft drinks was not predicted.

One study never proves anything, especially in nutrition, a notoriously difficult science.  But this study appears well designed with no obvious (to me) methodological flaws, and there is some precedent from another very highly regarded study:
     

Diet soda also was positively associated with incident MetSyn, with those in the highest tertile of intake at 34% greater risk than those in the lowest tertile. The strength of this association was surprising. However, it is consistent with recent data from the Framingham Heart Study, which found a 56% increased risk of MetSyn among those consuming (greater than or equal to) 1 serving of diet soda per day.

 
A weak association with sweetened drinks was not statistically significant in this study.  The authors draw no positive or negative conclusion from this but they are careful to point out that other studies have shown that sweetened drinks also have negative consequences.

I've been watching for a result like this ever since laboratory studies indicated that artificial sweeteners can fool the body into releasing insulin.  The body tries hard to keep blood sugar chemistry within a certain range; misregulation of insulin levels can't possibly be good for us.  I have this image in my head of gangs of rogue insulin molecules, unemployed due to lack of sufficient sugar, wandering the bloodstream and looking for trouble.  

Tags: diet, nutrition, health (all tags)

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  • what's MetSyn? (0 / 0)

    Can you explain more what that is? I don't drink a lot of soda, but when I do I sometimes drink diet soda. How much intake are we talking about here?

    by Stacey on Thu Feb 07, 2008 at 03:12:06 PM PDT

    • metsyn (0 / 0)

      Metabolic syndrome (MetSyn) is a loosely defined aggregate of preclinical conditions that when combined are highly predictive of problems down the road.  It's defined based on threshhold measures of weight, triglycerides, cholesterol, blood pressure, and probably some others I'm forgetting, but you don't have to have all of them.  Metabolic syndrome is not a disease, it's a very serious warning.

      I found the following statement in the simplified clinical statement at the end of the paper:

      Interestingly, adults who consumed 1 serving of diet soda a day had a 34% higher risk of MetSyn compared with nonconsumers.

      From reading the paper itself I don't think they directly compared 1 daily serving vs none - it's highly unlikely that they had significant populations that drank exactly these amounts.  What they really did was divide the population into thirds depending on their intake, eliminated the middle group, then compared the high intake group to the low.  The highest group on average probably drank diet soda daily while the lowest drank it rarely.

      by lyn on Thu Feb 07, 2008 at 05:46:24 PM PDT

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      • Can you control for lifestyle, though? (0 / 0)

        For instance, how do you control for those who are or were overweight and are drinking diet soda to lose or maintain a lower weight? I'd assume those who drink diet soda are more likely to have other reasons to drink it.

        "You're never more alone than when you're alone in a crowd."

        by Expat Briton on Fri Feb 08, 2008 at 10:37:55 AM PDT

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        • just the basics (0 / 0)

          Lifestyle factors are things like smoking and exercise - non food related factors that influence health.  And while people drinking diet soda may have a different diet than people drinking regular soda, that's not actually difficult to account for in the analysis.

          Motivation is not one of the factors studied.  I imagine most people who are drinking diet soda do so because they think it will help them keep their weight down.  But the reason for drinking it is less important than what the final diet ends up looking like.  I don't know whether the researchers looked at estimated calorie intake - it tends to be so extremely unreliable that researchers have more or less abandoned it in studies where you need to rely on accurate recall.

          This was a 9 year study that monitored diet using a standard food frequency questionnaire - for the most part researchers have a good sense for how closely it tends to represent reality.  But one major reason nutrition studies tend to be unreliable is because people are unreliable when they talk about food.

          by lyn on Fri Feb 08, 2008 at 10:56:05 AM PDT

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  • hasn't done that for me (0 / 0)

    I have a family full of diabetics(adult onset)and I still have good blood sugar levels,in my mid 50s and the age my dad and his siblings became diabetic. I drink a lot of diet sodas. I would watch this research closely - a lot of us who drink diet have not-so-good food habits in other areas(I admit this)and it may be so with the study's subjects.

    As a child I know I lived on Coke until I got tired of the taste! Really! I was about 9 when that happened.

    by chun yang on Thu Feb 07, 2008 at 04:27:26 PM PDT

    • I'm glad to hear that. (0 / 0)

      I've been trying to balance this stuff in my mind. On the one hand, I know artificial sweeteners aren't good for you. On the other hand, thanks in part to diet soda I've lost 30 pounds, and that is good for you. Makes my head hurt.

      by Rick Massimo on Thu Feb 07, 2008 at 06:12:25 PM PDT

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      • healthy weight is definitely key (0 / 0)

        That's great if the diet soda helped you lose weight - the extra 30 pounds is probably more important than any one dietary factor.  Unfortunately most people aren't so lucky.  One of the great mysteries of the past 30 years is why there isn't more evidence linking diet soda to weight loss.  It's a no-brainer that substituting a zero calorie beverage should result in lower weight, yet the most rigorously controlled studies keep showing no difference between diet and regular soda, no matter how hard they try to keep other factors the same.  A few studies have actually shown the diet drinkers gaining more.  There are plenty of theories, but no one really knows what's going on.

        by lyn on Thu Feb 07, 2008 at 07:28:41 PM PDT

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      • same here (0 / 0)

        I lost 40 pounds and have kept it off for more than 7 years now, and switching to diet soda was a big factor. I make it a point not to drink anything with calories in it, and I need something other than plain water every now and then.

        My diet soda intake is limited to one of those small 8-ounce cans with dinner.

        Of course, when I was pregnant I stopped drinking diet soda altogether...just in case.

        by Erika on Thu Feb 07, 2008 at 07:36:46 PM PDT

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    • other factors (0 / 0)

      No, they account for other factors in the diet.  Each food group is analyzed with adjustments for the other food groups, in addition to also adjusting for demographic and behavioral factors.  In addition, they found that the subjects could be grouped for analysis into two major dietary patterns, a 'western' pattern (high in refined grains, meats, fried foods) and a 'prudent' pattern (high in fruits/vegs, fish/poultry, whole grains).  So they have a pretty good sense of the other factors influencing risks.

      by lyn on Thu Feb 07, 2008 at 06:19:25 PM PDT

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  • I am so over studies right now (0 / 0)

    Especially with the release of this news. A U of W study was partially halted when it was discovered that aggressive targets for blood sugar control led to higher death rates, rather than the presumed lower death rates.

    As a diabetic, I find that aggravating. It seems that although it seems obvious that low blood sugar=increased health, no one has actually studied it until now. Turns out we might be wrong and aggressive diabetic treatment might be a bad thing. This is, as the kids would say, "kind of a big deal."

    That's a big oops about a very well studied disease. So I think any study about a disorder as vague and amorphous as Metabolic Syndrome has to be taken with a large grain of salt. They are finding relationships, but not true causal effects. These are babysteps--not something to make lifestyle decisions by.

    Regarding insulin, excess insulin molecules always have sugar to work with. If you have excess insulin and are otherwise healthy, your liver will break down your glycogen stores and excrete more glucose to compensate. Personally, I've never had a blood sugar decrease in association with artificial sweeteners.

    I know, some of you guys have seen me on my 'medical studies in the media' soapbox before. I love science, research and doctors, (In fact I just kissed a doctor about 30 minutes ago!) but I sure wish the media would stop reporting every little study likes it's gospel.

    by sangfroid on Thu Feb 07, 2008 at 07:13:07 PM PDT

    • The media almost never gets it right (0 / 0)

      Actually I haven't seen the media spin on this one, I went straight to the journal.  There is a heck of a lot of bad epidemiology out there, but this study is well designed in a way that gets around many of the flaws typical of cross sectional and observational studies.  

      What do we really know?  What should we really know?  Are artificial sweeteners safe?  I don't think that question's been answered; I'm not sure it has properly been asked.

      After decades of research there is basically no evidence that diet sodas are beneficial to weight loss diets.  Yet people keep chugging them, despite the complete absence of long term safety data.  Three things we do know:  1) we have a skyrocketing diabetes rate, 2) we have a skyrocketing obesity rate, and 3) we don't know what is causing either.  

      From the conclusion section of the paper:

      Additional research on the relation between diet soda and incident MetSyn is clearly warranted.
      MetSyn is, by its very nature, a heterogeneous outcome. At present, no single pathogenesis has been elucidated, and it is possible that one does not exist. Regardless, MetSyn has been shown to be a good marker of future disease risk, and understanding how food intake or overall dietary pattern relates to MetSyn as an entity is valuable.

      And with typical researchese understatement:

      The fact that 60.5% of the ARIC population either had
      MetSyn at baseline or developed MetSyn over the 9 years of follow-up foreshadows a worrisome trend for the burden of MetSyn in the United States.

      by lyn on Thu Feb 07, 2008 at 08:47:46 PM PDT

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