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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,
Episode #487
image of saltine crackers

Why the Cracker Test Is Crackers

There are are so many flaws in this argument, it’s hard to know where to begin.

I’ll start by saying that the cracker test is not a reliable indicator of your genetic makeup...or even your salivary amylase production. For one thing, the change in flavor is subtle. If you’re expecting that saltine to start tasting like cake, you'll be chewing a long time. Our perception of sweetness is also greatly affected by our customary intake of sugar (and even more so by artificial sweeteners). Someone who rarely consumes sweetened or artificially sweetened foods may be more likely to perceive that subtle sweetness than someone whose taste buds are accustomed to a higher level of sweetness.

Of course, there are more legitimate ways to measure the amount of salivary amylase, but they involve test tubes and reagents, not saltines. Even so, the levels of amylase in your saliva aren’t determined only by your genes.

Salivary amylase levels vary throughout the day; they are likely to be much higher in the evening than in the morning, for example. Psychological stress can also cause a surge of salivary amylase. In fact, researchers often use it as a marker in studies looking at the impact of stress and stress interventions. Caffeine can stimulate salivary amylase production. Smoking and green tea can inhibit it. An increase in body weight can down-regulate amylase production. And so on.

With all of that noise, I don’t think we can use salivary amylase levels as a reliable marker for our genetic disposition to carbs. And even if we could, there’s another glaring logical flaw in this theory.  

There are more legitimate ways to measure the amount of salivary amylase.

Let’s say I am descended from hunter-gatherer stock and, as part of that genetic heritage, I have lower salivary amylase levels. As a result, my body’s ability to break down starches is slightly diminished, meaning that I will absorb slightly fewer calories from the starches I eat. Twenty thousand years ago, when food was harder to come by, that may have been a disadvantage. Today, when food is overly abundant and we tend to consume more than we can use, this starts to sound like an advantage. Undigested starch, after all, can also be described as fiber.

Now let’s say that I follow the advice given by proponents of the cracker test. Because I have lower salivary amylase production, I drastically cut down the amount of carbohydrates in my diet, replacing them with the exact same number of calories from protein and fat. Instead of some of the starches from my brown rice and sweet potatoes passing through me undigested, all of the calories from my bone broth and nut butter are being absorbed. In this scenario, I would end up gaining weight! In fact, research has found that, among people with fewer copies of the amylase-producing gene, those who eat more starch tend to weigh less than those who eat lower-carbohydrate diets.

That said, the impact of salivary amylase on starch digestion (and its relationship to body weight) is modest. The vast majority of starch digestion occurs in the small intestine and is unaffected by the genes that determine salivary amylase production.

Finally, keep in mind that starch is not the only type of carbohydrate in our diets. Fruits, vegetables, and dairy products all contain carbohydrates in the form of simple sugarsand these would be unaffected by high or low salivary amylase levels. So, even if the cracker test were a reliable way to determine your genetically-ordained ability to digest starch, the idea that the percentage of carbohydrates in your diet should be dictated by your salivary amylase levels isin my opinioncompletely crackers. 

Image of saltine crackers © Shutterstock

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