What Does 'Less Than 20 Parts Per Million of Gluten' Mean?

Question: What does it mean for products to have less than 20 parts per million of gluten?

Answer: You've almost certainly seen references to "parts per million" on various gluten-free products — i.e., "This product contains less than 20 parts per million of gluten," or "Tested to contain less than 5 parts per million of gluten."

But what does this mean in terms of how much gluten the products actually contain?

Bear with me, as this actually gets fairly complicated.

Parts Per Million Defined

The term "parts per million" measures the percentage of one substance as a part of another substance. For example, if a huge barrel of marbles contains, say, one million marbles, including 999,999 plain white marbles and one sparkly red marble, then that barrel contains one part per million red marbles. You also can describe that as 0.0001% red sparkly marbles.

If that same barrel contained 990,000 plain white marbles and 10,000 red sparkly marbles, then it would contain 10,000 parts per million, or 1% red marbles.

Now, when you're talking about parts per million (or percentages), the size of the barrel doesn't matter as long as the ratio of plain white marbles to sparkly red marbles stays the same.

Make sense?

Parts Per Million as It Relates to Gluten

Now, you may not realize that most "gluten-free"-labeled commercial food products still contain a tiny bit gluten, although some contain less than others.

Foods that contain 1 part per million of gluten contain 0.0001% gluten as a percentage of the food, while foods that contain 20 parts per million of gluten contain 0.002% gluten.

That's not a lot of gluten, but it only takes a tiny bit to give you a reaction. (How little? Check out How Much Gluten Can Make Me Sick?

for the answer.)

While some people with celiac disease or non-celiac gluten sensitivity may do just fine with foods that test right at the legal limit (less than 20 parts per million of gluten), others will react to far lower levels.

Obviously, the more foods you eat that contain a tiny bit of gluten, the more gluten you're consuming overall (remember, parts per million is a percentage, not a fixed quantity).

If you're careful to choose foods with lower parts per million numbers, you'll be getting less gluten overall: one pound of something with 20 parts per million contains twice as much gluten as one pound of something with 10 parts per million of gluten.

Still with me? Lower is better when it comes to parts per million.

How Much Gluten Did You Eat Today?

According to the University of Maryland, people who eat a "standard" gluten-free diet with plenty of gluten-free grain products consume about half a kilogram (a little more than one pound) of gluten-free-labeled grain products a day (hey, those servings of gluten-free cereal, pizza and bread can add up!).

Since those gluten-free-labeled grain products most likely contain between 10 and 20 parts per million of gluten each, someone who consumes that much "gluten-free"-labeled food per day actually is consuming a total of between 5 and 10 mg per day of gluten.

Some manufacturers of gluten-free products are more diligent than others in making sure their products go well beyond the legal standard of less than 20 parts per million of gluten. For a guide to manufacturers' parts per million testing limits, check out How Much Gluten Does Your 'Gluten-Free' Food Contain?


University of Maryland. How Much Gluten Is Safe For Me? Press release, Aug. 4, 2011.

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