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What Is the Cracker Test?

Some claim that chewing on a saltine can reveal how much carbohydrate you should eat. Nutrition Diva thinks this is completely crackers.

By
Monica Reinagel, MS, LD/N, CNS ,
July 24, 2018
Episode #487

Jennie writes: I recently heard about something called the cracker test. We did the test in our family and the cracker did not get sweet for any of us. Apparently this means that we should only eat 25% carbs. I’d love to hear your comments.

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Raise your hand if you know what the cracker test is. I first learned about it in high school biology, as part of a unit on human digestion.

What Is Salivary Amylase?

Digestion, we learned, begins in the mouth. As you chew your food, it’s mixed with saliva, which contains an enzyme called amylase. This enzyme helps to break large starch molecules down into smaller sugar molecules. Fortunately for those who don’t chew very well, the digestion of starch continues in the small intestine, courtesy of starch-digesting enzymes secreted by the pancreas. In fact, only about 5% of starch digestion occurs in the mouth, so even if you swallow that bite of bagel whole, you’re still going to digest most of it.

Meanwhile, back in high school, the cracker experiment was a fun way to demonstrate the action of salivary amylase.

How Does the Cracker Test Work?

Here’s how to do it at home: take a bite of an unsalted saltine cracker and chew it without swallowing. As you chew, you may perceive a subtle shift in the taste as some of the starch in the cracker is converted into sugar by salivary amylase enzymes. Learning is always more fun when it involves snacks!

But now the cracker test is taking the internet by storm. It’s being promoted as a way to determine how much carbohydrate your body can tolerate. According to proponents, the length of time it takes for the cracker to start to taste sweet in your mouth determines the percentage of carbohydrate your diet should contain. The longer it takes for the cracker to taste sweet, the lower your carb intake should be.

The Evolutionary Role of Salivary Amylase

It’s true that there are genetic differences that affect the amount of salivary amylase we each produce. These differences are thought to be an evolutionary response to different diets. Let me explain: In agricultural societies, where starch intake tended to be higher, natural selection favored genetic variations that led to greater salivary amylase production. Why? Well, if you had more salivary amylase, you’d be able to extract just a little bit more energy out of a high starch diet. In a time when food was not as abundant as it is today, this would be a survival advantage.

Hunter gatherer societies, on the other hand, tended to have a lot less starch in their diets. These societies might still have experienced random genetic variations that resulted in some people having more salivary amylase. But because this conferred little survival advantage, it would not have been selected for in these populations. As a result, someone of Egyptian descent (one of the first places that agriculture flourished) may produce more salivary amylase than someone descended from the indigenous peoples of North America, to which agriculture came much later.

Of course, as we’re all finding out thanks to mail order DNA sequencing, our genetic makeup is a lot more mixed up than many of us realized. You really can’t rely on your last name or the language your great grandparents spoke or even your skin color to know what’s in your genes.

In any case, the cracker test is supposed to be a quick and easy way to determine your salivary amylase levels and, by extension, whether your genes are built to digest bison or baguettes. If it takes a long time for the cracker to taste sweet, it suggests that you have less amylase in your saliva. Therefore, the theory goes, you’d be better off limiting the amount of starch you eat.

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