Some of you might remember this post that I did about soda (or soft drinks, or pop, depending on where you are from) several months ago. The major conclusion, for those of you feeling too lazy to follow the link, is that regular soda is an easy way to overload on sugar--therefore, avoiding soda can help reduce the chance of sugar-overload problems like excessive body fat, poor blood glucose regulation, and tooth decay. 1-2 diet sodas per day might be ok but it's hard on the wallet. For me--show me good scientific evidence that an excess of one thing causes problems (e.g. soda is a calorie bomb influencing weight gain) and I will consider that good enough. Apparently I am in the minority, however, as I am still seeing articles like this one: This is what happens when you drink soda. Some of the claims I have written about before, but there was enough new material that I thought I had to make a comment or two (or eight). Ready?
1) Brain. I love how these articles never seem to provide a link to the actual study, or at least a summary. Probably because if one does actually link to it, you will not always find things to support your premise. The "study" reference 1) utilizes a high saturated fat/high sugar diet, not just a high sugar diet; 2) doesn't say (in the blurb anyway) where the sugar and fat was coming from; and 3) was a study conducted in rats and not humans. So, 1) we don't know if the reduction of BDNF comes from saturated fat, sugar, or the combining of the two; 2) there are different kinds of saturated fat out there--was it from meat/coconut/chocolate, etc, and what form did the sugar take; and 3) humans aren't rats. I definitely see some potential for more research, and a few alarm bells going off, but I can't make any recommendations based on a non-human more-than-just-excessive-sugar study.
2) Teeth. I already talked about the problems with regular soda and problems with EXCESSIVE phosphoric acid consumption here. Unfortunately they are making statements in this article that are patently false, particularly the one about diet soda having a lower pH that regular--it doesn't take more than a quick Google search to find out that on average regular sodas have a lower pH than diet sodas. Oh, and while we are on the subject, battery acid has a pH of 1.0, so regular and diet sodas with a pH of 2-4 are obviously not as acidic if you have a basic knowledge of chemistry. Also, for your entertainment pleasure, I found this little study in which slices of freshly cut tooth enamel were soaked in sodas for 48 hours straight, and then a spokesperson from the American Beverage Association (obviously with their own bias) had to point out that this doesn't mimic "real life" conditions (no saliva to buffer, etc), and I had to say the beverage dude has a point--it's hard to take recommendations seriously when you haven't noted your own flaws. Oh, and while we are on the subject of acidity, let's talk about dosage here. If you followed the link that has the pH values--I noticed that two of my favorite add-ons, lemon juice and vinegar, have a lower pH than any of the sodas listed (and think of all the people who claim that apple cider vinegar cures everything!). Now, granted, if I would actually drink a soda I'd probably get more of an infusion of acid that when I put the vinegar all over my salad; but I'm not drawing a false equivalency of saying "all things that are acidic are bad." (Yeah, I've had people who do drink enough regular soda that they probably do have it in their mouth for most of a 24 hour period, but can you apply these same statements to 1-2 diet cokes per day? Likely not).
3) Heart. Have I pointed out the problem with observational studies lately? Like, how they usually rely on unreliable instruments like food frequency questionaires in which people have to try to remember how much soda, etc they've consumed (when they probably have trouble remembering where they put there car keys at)? Have I also mentioned that correlation does not equal causation? Observational studies have a purpose--to establish a link so we can do a controlled study later on. Period. Amazing how people forget this when they have an agenda to push--but remember it very quickly once someone attacks their favorite food. Moral of the story here--I'm not making recommendations based on someone's memory--and neither should anyone else.
4) Lung. Already covered the whole sodium benzoate thing previously as well, and with the development of COPD we are right back to the "observational study" and "correlation does not equal causation" statement again. Just as an FYI, however, if someone already has COPD, particularly if you are already requiring oxygen, if you consume excessive amounts of carbohydrate from any source you are going to increase your carbon dioxide load--in other words your breathing is going to become even more difficult. If you have COPD, and you happen to be getting excessive sugar from soda--you probably want to cut back on that or cut it out.
5) Bones. I know, you've already read the link before where I talked about this. So, maybe it is the phosphoric acid, or maybe it is just because you have a crummy diet overall and don't do any muscle building exercise. Or maybe all of the above. It's worth thinking about, but I would hate to concentrate on someone's soda intake, particulary if it's limited anyway, and not think about what else they might be missing.
6) Kidneys. Observational study, covered the acid thing before, etc. Now, another FYI for you, if you have end stage renal (kidney) disease and are on dialysis, you have to limit your phosphorus consumption period (so no colas, but no dairy or nuts either).
7) Digestive system. They are on to something here, but we are talking about one section of the population (which unfortunately includes me)--people with irritable bowel syndrome. So, yes, if you already have trouble with bloating and flatulence (and the pain that comes with it), and you don't want to make it worse, you probably want to avoid carbonated drinks. Some of us with IBS do not tolerate fructose very well (meaning that you might get diarrhea or constipation bloating) from excessive fructose, so avoiding high fructose corn syrup sweetened things is also a good idea (unfortunately I also have to avoid too much fruit as well). The sweeteners in the sodas, however, are not usually known for having a laxative effective. The confusion probably stems from the fact that many "sugar-free" candies, etc, contain sorbitol or other sugar alcohols which can have a powerful laxative effect (that's also why prunes and prune juice can help laxation, because of the sorbitol content).
8) Weight. Take is excess calories and carbohydrate from anything, particularly in liquid form so that you really don't feel full, and you will gain weight. Death "caused" by soda on the other hand? Maybe if a pallet of soda crushes you, you could say that. And interacting with genes that regulate weight? Perhaps they were confusing that with interacting with hormones such as insulin which play a prominent role in appetite? Some of us are genetically predisposed toward insulin resistance, but that's thanks to our parents, not because of soda.
Take home message--Regular consumption of "regular" soda will make weight control, blood glucose control, and dental health extremely difficult because it is a readily available source of excess carbohydrate. Consuming more than 1-2 diet sodas per day might be problematic, but the evidence is much weaker. And "evidence" that is false or misleading is not evidence.