Wednesday, October 29, 2008

Nutrition News Update: Kidney Stones in Children

The New York Times reported yesterday that according to some doctors, kidney stones are showing up in kids more often. While reporter Laurie Tarkan does a decent job explaining that some pediatric kidney stone cases might be caused by diet, I think she is missing something crucial. And ironically the answer lies in the main photograph of the article, which depicts a girl sitting at a table with a tall glass of cola. Ms. Tarkan lists two nutrition-related causes of renal stones: too much salt and not enough water. The reason is that both of these create too much calcium and oxalate in the urine. She also mentions obesity, sucrose in colas, and high protein diets as possible causative factors. In fact, many theories are proposed in the medical literature, but there is still no consensus or there could be various causes and various types of stones.

I would like to propose another idea: As Ms. Tarker mentions, toxic chemicals such as Melamine can cause kidney stones. But what about a less infamous ingredient: phosphoric acid. Phosphoric acid is added to colas to provide a tangy or sour taste. Phosphoric acid has been correlated to osteoporosis due to the fact that it can pull calcium from the bones. There is even some solid evidence to back this up. When compared to citric acid colas (i.e. Sprite), the phosphoric acid colas (even diet colas!) were more like to cause kidney disease. Colas have also been shown to cause changes in calcium-oxalte formation in the urine, which would further bolster this theory. Other theories are abound, including causes such as flouridated water and too much vitamin C supplementation- another reason why over-supplementing is a bad idea.

So what should you feed your children (and yourself) to prevent kidney stones:

1. Water makes the urine less concentrated so it is less likely to form kidney stones. Children should not be introduced to colas. Their primary source of fluids should be milk and water. Even 100% juice should be limited because it replaces water. Remember, if they see you drinking tons of cola, they will want some too. Be a good role model.

2. Choose foods with less salt. Excess salt primarily comes from processed foods. So whenever possible, make food from scratch and use a combination of herbs and sea salt (in moderation) to flavor food.

3. Never put kids on a high protein diet if you think they are overweight. Some people believe that high protein diets cause kidney stones due to the breakdown of animal protein into uric acid. Although, this theory has not yet been proven, children should receive protein from multiple sources including vegetables and whole grains. And of course, exercise will help kids lose weight too.

4. Instead of supplementing your kids with vitamin C when you think they are getting sick, try giving them vitamin C-rich foods such as citrus fruits, cantelope, tomatoes, broccoli, cabbage, and red peppers.


  1. I read that article and thought it was so interesting...nice take on it...

  2. Excellent point, I pulled the paragraph about phosphoric acid colas and plopped it into our comment section in the 'kidney stones in kindergarteners' post and will ask our own RD to look into this more fully, since you are all far more qualified than I am to venture an opinion on the whys and hows...

    That said, I can certainly speak to media and marketing's impact on kids and the reverb taking place there when it harms kids' health like this! Sheesh. Accountability of public health over profiteering, anyone? sigh.

    Here's my comment back atcha on our blog...thanks, Debra! Come visit again soon, and feel free to ping me with a guest post anytime you want to sound off like this on a similar subject; important work! Best, Amy