I was going to call this post “nobody knows the trouble I seen” except that it seems ludicrously self indulgent to whine that one has been living through construction hell when the rest of the world has revolutions, civil wars, hurricanes and so on to contend with. (But, to paraphrase Will Rogers, everything is manageable provided it’s happening to someone else.) This isn’t to say my curmudgeonly instincts have been dormant . One particular item a while back had me seething.
“Sugary drinks are not so sweet” was the headline in the Health section of the Globe and Mail (24 May 2013). Apparently, drinking a sugar-sweetened drink a day not only rots your teeth and adds up to empty calories (with the added bonus that it makes New York’s Mayor Bloomburg crazy) but “may increase the risk of kidney stones”. Gasp. I had to pause to take a sip of my ginger ale* while that sank in.
I puzzed and I puzzed, to reference one of my favorite curmudgeons, the Grinch. Didn’t make sense. How on earth could fructose cause blobs of crystallized minerals to form in the kidney? (To reinforce the point that sugary drinks are Evil the accompanying photo was of a surgeon with a scalpel. Someone had fun with that.)
The research cited was from 2007, published in a journal called Kidney International (2008, 73; 207-212). The worthiest journal nobody’s ever heard of. My curiosity got the better of me and I downloaded the article and read through the cringe-inducing prospective study; yet another data-mining expedition hoping to find a “link” between X and Y. (For more on my distaste for the term, see post.) The data? From – wait for it – the appalling Nurses’ Health Study, formerly used to “prove” that taking estrogen was just a boffo idea. Here, the research cites some 19,000+ women along with some 46,000 men from the Health Professionals Follow-up Study. Impressive numbers. Pity the hypothesis is so feeble.
Not of course to our heroes, researchers Taylor and Curhan, unspecified experts at a renal division/lab at Brigham Young and Harvard who engage in enough statistical jiggery-pokery to make the world go round. (Pity nobody blinks when data gets tortured.)
Just a few problems here. As I explained, in often far too exhaustive detail in The Estrogen Errors, extrapolating to the general population from the Nurse’s Study is massively problematic. For starters, there’s its basic design, bi-annual self reports, which are notoriously unreliable. We’re all prone to error as any gibbon with half a brain knows: we forget, lie and generally get things wrong. Good grief, most of us stutter when they ask us how much we weigh when we get a new driver’s license. Plus, there’s the healthy user bias – people who respond to any questionnaire tend to be richer, smarter, better off, i.e., healthier than the average bear. Er, person. Often they’re white and frequently younger. All of which means they are not like the real at-risk population who, by and large, tends to be poorer, less educated, older, more diverse, less health and diet conscious, more stressed and sicker. Face it, d’you think you’d have time to sit around reading some blog if you had to work at two or more minimum wage jobs just to put food on the table and pay your rent? Could you even afford an iPad or even high speed internet?
This is on top of the fact that professionals in general can’t stand in for “everyone” and basing one’s conclusions of what these people do (or say) is what’s popularly known as being spectacularly wrong.
What really interested me, though, was what these researchers thought might be going on physiologically. In other words, how did we get from basic sugar metabolism to blobs of crystallized minerals in the kidney? Gremlins? Evil spirits? The authors do obligingly admit that the underlying mechanisms are “unknown” (ah, ya think?!) but postulate various processes, none of which make sense. Hence their masterful use of language:
“Fructose may also increase urinary excretion of oxalate, an important risk factor for calcium oxalate nephrolithiasis. Carbohydrates, along with amino acids, provide the majority of the carbon for glyoxylate and oxalate synthesis, and fructose may be an important dietary sugar influencing the production of oxalate.” (emphasis mine)
The authors concede backing for their hypotheses are “sparse”; personally I would have said nonexistent. Rats make up the bulk of their research subjects in this section and the one study they cite using humans consists of eleven – yes, 11 – men whose pee was analyzed for calcium loss (versus calcium intake). Fructose intake made no difference in the calcium these men excreted but the researchers still concluded that the reason fructose laden drinks caused kidney stones “may be related to the effect of fructose intake on urine composition”. How they concluded this I have no idea. Maybe they were on a sugar high.
The only marginally plausible explanation had to do with uric acid metabolism and for a moment I thought, OK, this might make sense. Then I checked the reference and realized it only applied to people with gout, whose uric acid metabolism is already dysfunctional (that being the definition of gout).
Kidney stones, by the bye, are hardly that common and rarely if ever life threatening. Even Wikipedia’s overblown, hyperventilating piece on the topic, that sounds as though it was written by a nephrologist who had just passed one, admits that the incidence or number of new cases a year is “0.5%”. (Of course it doesn’t specify 0.5% of what which is rather an important point, but let’s not nitpick at this late point in the post.)
How did this 5-year-old study even make it into the health news section? Having spent some years as a medical writer and journalist, I can tell you exactly how. A group of people in an editorial meeting, drinking coffee – or pop – were bouncing around story ideas and someone suggested a piece vilifying soft drinks, currently Public Enemy No. 1 (see NYC, Bloomburg). So, they wrote the headline then they contacted the hapless writer who cast about for some new and nifty problem that could be blamed on aforesaid sugary drinks. Everyone knowing full well that the majority of people only read the headline and the first paragraph; it’s only mutants such as myself who check the original research and parse the methods section.
If sugary drinks do give you kidney stones, these people didn’t prove it.
There are a lot of good reasons to consider soft drinks a treat, not a staple. They’re empty calories; they rot your teeth and many of them contain fairly high amounts of caffeine which can make you nervy and insomniac. But kidney stones? Really?! We think not. And it takes stones to say they do.
* oh get over it. It’s summer. There’s construction outside. Yes, I have the occasional ginger ale or Coke. Sometimes, when I’m especially cranky, two days in a row. Sue me.