Lose weight. Think better. Boost productivity. Live well.

The Six Types of Sugar We Eat

Here's the difference between glucose - which your body needs - and the rest of the sugars, which your body tolerates.

Now hear this: You don’t need to eat sugar. Humans never have, and humans never will. I want to start there because even after hiring a writer to research the topic of this article – which is how sugar affects your memory – my writer turned in an 800-word piece with the following subheading in 20-point bold font:

                                 “You need sugar, but not too much”

I would have accepted any one of the following subheadings:

  • Your body needs glucose, but not too much
  • What your body does with the excess sugar you eat that it simply can’t use
  • The body’s amazing ability to convert 80% of your diet into blood sugar
  • Here’s exactly how much blood sugar your body needs

These aren’t great subheadings. I think they’re awful, in fact. But neither of the above subheadings would have caused me to cringe, sigh, and lower my head in despair. After reading this subheading I immediately knew that she had not understood what she read.

Shame too.  Because the overconsumption of sugar is literally killing us. So, before we dive into the impact sugar has on your neurocognitive abilities, I want to run help you understand that there are different types of sugar.

The Six Types of Sugar

There are six different types of sugar, each one chemically different from the next, and all come from different sources:

GlucoseMade by your liver from the carbs you eat. Glucose is blood sugar. It is the body’s primary energy source, unless you are practicing a ketogenic diet or another ultra-low carb diet, and your body now uses ketones for fuel. Your body breaks down food, turns it to glucose (if it can), uses a portion of the sugar, stores a portion of the sugar as glycogen to use later for energy, then converts that it can’t use to fat.

Fructose – This is fruit sugar. And it’s great when you get it while you’re eating (not drinking) fruit. When you get the processed fructose in high doses – like the kind of stuff that shows up in junk food, fruit juices, soft drink, and sweets – it is dangerous. Fructose is processed in the liver, but not stored as glycogen, so what you can’t burn gets immediately converted to fat.

Sucrose – Table sugar. This is the stuff with which we are most familiar. Sucrose is a major component of cane sugar and beet sugar and fruit. It is made up of glucose and fructose. The body must break it down in the liver and convert it to glucose before it can be used.

Galactose – This is a component of lactose, the sugar you get from milk and yogurt. It is absorbed and metabolized the same way as glucose.

Maltose -Maltose is a plant sugar, usually found in grains so it’s naturally occurring in many cereals. It’s only about one-third as sweet as sucrose, but it’s used in hard candies and frozen desserts because it has a high tolerance for extreme temperatures.

Lactose – Milk sugar. This sugar is the result of galactose combining with glucose.

You Need Glucose, But Only a Little

I think that’s what the writer was going for. She would have gotten there eventually.

What may have confused our writer, and what probably confuses most people is that the body needs glucose, which is “sugar.” There’s no doubt about it. As a Harvard Newsletter “On the Brain” tells us, glucose is a primary energy source. For most people, it’s the default energy source for every cell in the body.  The brain drinks up about half of all the sugar energy in the body.  If you don’t provide your brain with enough glucose, you will experience a noticeable decline in cognitive function and attention abilities. But we also observe issues when people have too much sugar.


There is more than one type of sugar, and the reality is the handful of bodily functions that require glucose on a daily basis (as opposed to getting fuel from ketone bodies, for instance) only need a small amount of it for optimal performance.  And your body doesn’t need any of the other types of sugar to function. It just needs glucose.

How much?

The amount you would get on a typical classic keto diet – between 30g and 70 g of sugar a day from carbohydrates. Not fructose. Not sucrose. No maltose. Not lactose (though we love dairy in the keto camp). Glucose.

The ketogenic diet is set up to ensure you get the carbohydrates you need to get enough glucose in your blood so your brain gets what it needs to function optimally.

In part two of this piece (which you can read here), I’m going to focus on how sugar affects your brain, specifically your memory.

Comments are closed.