The Potato Paradox: What Coke and Potatoes Have in Common

Why it’s not as simple as sugar = sweet.

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Check out this riddle:

A woman ate a mouthful of sugar (glucose) but her sweet tooth registered zero. How did she do this?

Scroll for answer!

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Answer: she ate a baked potato.

A decent-sized russet potato has roughly the same amount of sugar as a can of regular Coke — nearly forty grams or 10 teaspoons. Source.

This bring us to the potato paradox:

How can potatoes contain a lot of sugar, yet not taste sweet?

The answer lies in the way that the potato’s sugars are delivered, and the way we detect sweet tastes.

To fully understand this paradox, let’s drill a little deeper into sugars and sweetness.

Potatoes versus Coke and fruit

Potatoes and Coke both provide your body with roughly the same amount of energy in the form of sugars — a little less than 150 calories worth.

However, their sugars differ in two important ways:

Sugar types

  • The sugar in sodas is very similar to the sugar in fruits and natural sweeteners (like maple syrup and honey). They tend to be a roughly equal mix of glucose and fructose. Most high-fructose corn syrups contains about 55% fructose and 45% glucose.
  • Vegetables and grains are loaded with glucose but contain little fructose (though sweeter veggies like carrots do contain some fructose).

Sugar chains

  • The sugars in sodas, fruits, and natural sweeteners (maple syrup, honey) enter your body as ‘singles’ or ‘couples’.
  • The sugars in starchy vegetables enter your body as long chains of glucose.

Why doesn’t the glucose in starches taste sweet while the glucose in other foods does?

How do we taste sweet?

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Your tongue is full of taste buds, which you can think of as miniature locks, connected to wires that reach various parts of your body. Each type of taste (sweet, salty, bitter, sour, and umami) has its own locks, with various keys. The keys can be sugars, salts, proteins, amino acids, or other molecule types (science is still sorting this out!).

While the taste sensation begins with your tongue, scientists are now discovering taste buds in other parts of your body, such as your gastrointestinal tract.

When starches enter your body, they don’t fit any of the ‘sweet’ locks because they don’t have the same shape as the single and paired sugars we enjoy.

Fun fact: It’s tempting to assume that we evolved to enjoy fruits, but in reality, plants evolved to coerce animals to disperse their seeds by making them yummy! It pays to have a plant biologist in the family (thank you Dr. Stephen Davis!)
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Fun fact: If you digested a starch molecule in a test tube instead of your body, it would become sweet as the glucose chains reached small lengths of one, two, or three. Indeed, maltose syrups have traditionally been made by digesting starch from barley with an enzyme that breaks apart the glucose bonds (barley b-amylase).

How do artificial sweeteners fit in?

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I can’t resist this ‘teachable moment’ on how artificial sweeteners work. They are chemicals that ‘tickle’ your taste buds and fool your into thinking you ate sugar, yet don’t fuel your body in the same way.

Potato versus Coke

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Despite their similar sugar content, there are several good reasons to favour potatoes — and other whole fruits and veggies — over Coke and other sweetened drinks:

  1. A serving of potatoes (and plants) provides not just sugars but also a solid dose of vitamins and minerals.
  2. Plant-based sugars are bundled with fiber. We don’t fully understand how fiber content affects blood sugar response, but we do know that fiber makes the whole package more satisfying so you are less likely to overeat. Plant fiber also fuels your gut bugs and helps your digestive system purr. This fiber is the reason that a potato is a better choice than a ‘vitamin water’ with sucrose.

Good news bad news

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The good news is that by understanding what potatoes are made of and how we taste sweet, we have solved the potato paradox.

The bad news is that we are left with more questions to answer:

Which is better (or worse) for your body: glucose or fructose? Remember, starches are pure glucose whereas fruits and other sweeteners have a mix of both.
Do starches and sugars affect your brain the same way? Are either or both truly addictive?

These questions need their own articles to do them justice!

Bottom line

I’ll leave you with one foolproof piece of advice when it comes to eating sugars:

Choose foods in which the sugars are bundled with fiber, and give you the most nutrients per gram of sugar.

If you want a baked potato — go for it — just know that it’s not a low-sugar choice, and compliment it with foods that meet the rest of your needs.

To further boost your carb IQ, check out Carbs 101!

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