Want another nutrition-related reason to keep eating wholesome, traditional foods you’d typically find in the farmers market?  How about avoiding painful kidney stones?

An article in today’s New York Times health section notes that, based on doctors’ anecdotal observations, kids today have a much higher incidence of kidney stones than kids had a few decades ago.  Kidney stones used to be primarily a concern for older adults, so the rise in childhood incidence is eyebrow-raising.  The article goes on to blame salt and dehydration.  In addition to cutting down on salt and chugging more  water, the article suggests, kids should cut down on fat too.

I started to get skeptical, like I often do when mainstream health information sources automatically cite a low-fat diet as a panacea, or roll out old standby scapegoats like salt.  Whether salt plays a role in kidney stones or not, if salt were the primary culprit in a rise in childhood kidney stones, then salt intake would presumably be on the rise, but according to these USDA data (excel spreadsheet), sodium intake in the United States has been virtually unchanged over the last fifty years. I also don’t think we’ve dramatically decreased our fluid consumption in the last few decades, and the article doesn’t try to justify a link to general fat consumption.

So what could be causing the increase in kidney stones?  The sharp increase over the last few decades reminded me of another childhood problem that has skyrocketed: obesity.  What if the roots are the same? 

Obesity, like most nutrition-related health problems, is strongly tied to recent dietary trends in which we see two themes: an increase in detrimental ingredients and a decrease in protective ones.  By detrimental ingredients, I mean foods typically found on the supermarket shelves rather than farmers market stalls: processed combinations of corn, wheat, soy, vegetable oil, sugars –– especially fructose –– preservatives, flavors, and so forth.  Protective ingredients look more like what your great-great-great grandmother might have eaten: grass-fed meats, fermented dairy and other fermented food, seafood, eggs, organ meats, vegetables, cod liver oil, and unrefined saturated fats like butter.  Protective foods from animal sources are often high in essential fat-soluble vitamins, especially A, D and K2, or in omega-3 fatty acids.  Clear out the fat-soluble vitamins and pump a kid full of high-fructose corn syrup, and you’ve got a few good building blocks for obesity.

It turns out an increase in incidence of kidney stones might have similar roots in these dietary trends.  Researchers looking at data from the Nurses Health Study (I and II) and the Health Professionals Follow-Up Study found that kidney stone risk is independently associated with high fructose consumption, and with insulin resistance.  The authors explain,

1. Fructose intake may also increase insulin resistance, which is associated with low urinary pH, a major risk factor for uric acid kidney stones. In addition, fructose is the only carbohydrate known to increase the production of uric acid...
   

Incidentally, fructose consumption has skyrocketed in the last few decades while the kidney stone trend has also been on the rise.  That’s only an association, but the study’s data show a strong link to fructose.  Increase in detrimental ingredients?  Check. 

So what about that second trend, a lack of protective ingredients?  Research suggests that presence of kidney stones is associated with deficiency in the ultra-important activator vitamin K2 (menaquinone 4), the vitamin Weston Price called Activator X.  Intake of this vitamin is on the decline, because it’s found in the kinds of once-common and prized foods we don’t eat as much anymore: organ meats, fish eggs, and grass-fed animal fat like butter, tallow and lard. 

You need the full trio of fat soluble vitamins (A, D, and K2 menaquinone-4) to absorb the vitamins and calcium correctly, as well as to secrete proteins that protect against kidney stone formation.  Kidney stones are crystalized minerals, often made up of calcium, particularly when calcium absorption and use isn’t functioning correctly.  Lack of protective ingredients?  Check.

For other nutrition geeks, it seems there’s a debate over whether fatty acids play a role in kidney stones, if omega-3s are protective and if omega-6s might be detrimental.   One study (full pdf) found that fish oil (omega-3) supplementation lowered kidney stone incidence whereas high omega-6 levels were detrimental.  The study also mentions that traditionally-living Eskimo cultures (they might have meant Inuit or been using the term more broadly; it’s unclear from the citation), eating a diet high in fish and saturated fat, lack kidney stones.  Finally, this article looks at some other potential dietary factors in kidney stone formation, although there’s very little detail about fat soluble vitamins.

I’m still sorting through this information, and don’t claim to be a kidney expert, but it looks like my usual standards of nutrition apply here.  If you want to avoid the diet-related health problems we see growing at an alarming rate, avoid the trends in eating habits we’ve seen over the last few decades, and make sure your kids eat well too.  Eat a diet of traditional, simple, locally-produced animal and vegetable foods, including vitamin-rich saturated fats.  Include some of the too-often-forgotten ingredients like organ meats and fish eggs.  And walk away from the vegetable oil and processed food aisles, or the aisles of sugared cereals marketed insidiously to kids.

Luckily, those aisles don’t exist at the farmers market. 

Some reading:

http://www.ncbi.nlm.nih.gov/pubmed/3489657 (Vitamin K and the urogenital tract. Abstract only.)

http://linkinghub.elsevier.com/retrieve/pii/S0306987706007171 (Chris Masterjohn’s piece on vitamin D toxicity redefined in terms of its relationship with vitamins A and K2)

http://www.westonaprice.org/basicnutrition/vitamin-k2.html (Also by Chris Masterjohn, some basic information about vitamin K2 menaquinone 4)

http://jasn.asnjournals.org/cgi/reprint/7/4/613.pdf (piece on n-3 and n-6: Anomalous Phospholipid n-6 Polyunsaturated Fatty Acid Composition in Idiopathic Calcium Nephrolithiasis)

Here’s another link, thanks to Stephanie:

http://www.kcrw.com/etc/programs/gf/gf081025halloween_history_me

http://ap.google.com/article/ALeqM5gKnKSn2RJcwce1BbdtdWmhkaBTnQD943FC0O0