Low potassium food - asparagus?

Question
I noticed that your site lists foods that are low in potassium.  Some (17) of your foods listed were also on a list of foods with high potassium at http://nutrition.about.com/od/foodfun/p/potassium_foods.htm

I am concerned about this as my mother needs to consume foods low in potassium.  Please double-check the following foods: asparagus, dried beans, carrots, cauliflower, celery, cherries, eggplant, kale, mushrooms, okra, peaches, pears, peppers, plums, strawberries, tangerines, watermelons.

Thank you very much!

Barb

Answer
Dear Barb,

Let me explain this to you using the example of asparagus. By the way, both Shereen Jegtvig (nutrition at about.com) and me at: http://en.allexperts.com/q/Special-Diets-768/Low-potassium-foods-meals.htm

listed it as a low potassium food. On the other hand, Dr. Agatson (e.g., at http://dietandbody.com/FAQ/2006/05/what-are-good-sources-of-potassium-for.html) consider it a GOOD source of potassium. Who's right?

The matter is, most if not all low potassium food lists, as well as most of the doctors, use potassium density of foods rather than potassium content in a certain volume or weight.

If you stop to think about it, any food can be low or high in any nutrient depending on serving size.

What's more, different food databases list different information regarding potassium content in asparagus. The matter is, most sources list such units as "cup" or "spear (large, medium, etc.) -- but who know how one cut or chops so the real weight in one cup can be different. Also, one can consider a spear small or medium depending on what she compares it with. Because of that, 1 cup can contain 365.82 mg (fitday database mg and another cup -- as little as 270.680 mg (netrition database.)

USDA food database is more solid: according to it, 100 grams of asparagus contains 202 mg of potassium -- but deviation is rather high: it can be 8.357 mg more or 8.357 mg less.

Potassium content depends also on ripening stage, spear diameter,  and the distance from the tip, so if your asparagus is cut short, it can be lower in potassium because the apical part has less of it. Another condition influencing mineral content is asparagus dryness. Completely dried asparagus has 373 mg of it in 100 grams of dry matter.

I hope the asparagus example can explain other discrepancies as well. The best way in these circumstances is to go directly to a reputable database and see how much of a nutrient contains a cup, 100 grams, an ounce, etc. of the food in question.

= Tanya Zilberter

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