What is PPM and Why Doesn’t “Gluten-Free” Mean Gluten-Free?

What is PPM and Why Doesn’t “Gluten-Free” Mean Gluten-Free?

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If you’re new to gluten-free living (and maybe even if not), you may have seen the abbreviation “PPM” thrown around, and wondered what it was.  Most websites dealing with celiac disease and gluten sensitivity (including this one) make frequent use of this term.  So what is it?

PPM = “Parts Per Million”

PPM stands for “Parts Per Million,” and is the unit used to measure how much gluten is in a food product. For example, 20 PPM means that there are 20 parts of gluten for every million parts of other ingredients. In practice, PPM is determined by weight, and translates to 20 milligrams per kilogram. In terms of percentages, if something contains 20 PPM of gluten, it means that .002% (two thousandths) of the product is gluten. 10 PPM means that .001% (one thousandth) of the product is gluten. 5 PPM means .0005% (five ten-thousandths).

“Gluten-Free” Doesn’t Mean Gluten-Free

So now that you know what PPM means, the next obvious question is “why does it matter?”  It matters because, at the moment, it is inextricably tied to the definition of “gluten-free.”  Logically, one would assume that the term gluten-free means one thing, and one thing only: zero gluten, right?  Wrong!  Zero gluten is indeed, one definition.  But unfortunately, it usually doesn’t mean that.  In most contexts these days–particularly when talking about gluten in food–the term “gluten-free” actually means something more along the lines of “extremely small amounts of gluten, hopefully approaching zero”.

People are often surprised when they find out that gluten-free foods can contain very small, trace amounts of gluten. Many people logically assume that gluten-free should mean zero gluten. And they’d be right… if we lived in a perfect world. So why isn’t it that simple? The short and simple answer is that gluten is so omnipresent in our food supply chain that it’s very difficult to keep it from working its way into everything else.  In other words, much like a virus, it sort of has a tendency to spread.

A Solution for the Majority

So, what do you do if you have celiac disease or gluten-sensitivity, but even the supposed gluten-free foods might not really be gluten-free? Well, studies have shown that the majority of people with celiac disease can tolerate trace amounts of gluten, up to 20 PPM, without adverse effects. For this reason, the US Food and Drug Administration, along with most of its international counterparts, has established 20 PPM as the limit for gluten contamination in any food that is labeled gluten-free.

So yes, there might be gluten in your gluten-free food.  But fortunately, chances are that it’s not very much.  If it’s labeled gluten-free it’s required by the FDA to contain less than 20 PPM.  If you’re typical of most people with celiac disease, you’re probably fine with gluten in concentrations lower than 20 PPM.

How Much is 20 PPM?

20 PPM really is an extraordinarily tiny amount of gluten.  A visual illustration of what 20 PPM is might help.  The following image contains 49,999 blue dots and one single red dot.  All of the dots were randomly placed on a white background, with none of them overlapping.  That red dot represents gluten, while the blue dots represent other “stuff” at a 20 PPM “gluten-to-stuff” ratio.  Can you see the red dot?  Look closely…  Give up?  Take a look at the second image below to see where it is:


Image of 49,999 dots and one red dot-a visual representation of 20 PPM


Image of 49,999 dots and one red dot, with the red dot highlighted-a visual representation of 20 PPM

As you can see, the gluten represents an extraordinarily small part of the whole.

As an aside, for those of you who are wondering how 20 parts per million can be represented by only 50,000 dots, it’s basic simplification of fractions.  20 in 1,000,000 is the same ratio as 1 in 50,000 (1,000,000 ÷ 20 = 50,000) .  I did that out of necessity.  I initially tried putting 20 red dots into a million blue dots, but the image either had to be incredibly large, which made it impractical for the website, or the dots had to be horrifically small, which made it impractical for you.  So, simplifying to 1 in 50,000 made it workable.


Now, before we just jump to the conclusion that 20 PPM is the answer to everything, hold the train!  There are undoubtedly some extremely sensitive individuals for whom 20 PPM is not sufficiently gluten-free. Such people can experience problems; even with foods that have a gluten concentration below 20 PPM, and are labeled gluten-free. Some of these people, however, might be able to tolerate smaller quantities of gluten, such as 10 or 5 PPM. For this reason, I try to perform multiple tests on products, using varying test sensitivity levels where necessary. This provides the ability to approximate the actual gluten content.

The graphs shown on product pages represent the number of tests that have been performed for that product at each of 3 PPM, 5 PPM, 10 PPM, and 20 PPM sensitivity levels. These multiple graphs are provided with the intent to help you evaluate a product’s suitability for your needs, based on your own knowledge of how sensitive you are to varying gluten levels.

So, if you know that you can tolerate products containing up to 20 PPM, all you need to do is look at the “< 20 PPM” graph to see how many tests have yielded gluten-free results at a < 20 PPM level. However, if you know that you’re sensitive beyond 20 PPM, you may need to look at the < 10 PPM graph, or possibly even the < 5 or < 3 PPM graph to get test results that apply to your circumstances.

Limitations of Gluten Testing

It’s important to note that with current technology, the limit of detection for even the most sensitive gluten test methods is somewhere between 2 PPM and 5 PPM, so it’s actually impossible at the moment to accurately test for zero gluten.  At the rate technology is advancing, hopefully that will change in the not so distant future.  Who knows?  Maybe there will come a day when gluten-free actually means what it says.  Until then, I suppose PPMs are here to stay.


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