Three Truths and a Lie About Sugar

Which carbs to shun, which to embrace — and WHY.

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As I sat sipping my latte in a trendy Vancouver café, I overhead a man lament “I can’t eat anything here! It’s all carbs, and I heard they evil”.

He was right about the sugar-laden pastry case, but was wrong to nix the whole grain hummus and veggie sandwiches. As a scientist, such misinformed oversimplifications drive me nuts. I had to restrain myself from giving him an impromptu science lesson on carbohydrates and health.

Instead, I channeled my frustrations into this article. It spells out clearly, using science, which sugars to embrace and which to avoid. As you’ll find out, there is far more to the story than “all carbs are evil” or even “all sugars are evil”. A little sugar in your life — from the right source — can be a good thing!

Let’s let sugar speak for herself in a game of “three truths and a lie”.

  1. My liquid forms are your worst health foe.
  2. Eating less of me does NOT guarantee weight loss.
  3. A spoonful of me causes LESS of a blood sugar spike than eating white bread.
  4. I am toxic to your body.

Scroll to get the answer!




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Lie: I am toxic to your body.

“Poison, toxin, venom are substances that injure the health or destroys life when absorbed into the system, especially of a higher animal.”

If sugars were indeed ‘toxins’, then sugars, and all their common sources, would be associated with poor health. This is simply not true.

The strongest evidence against the simplistic belief that “all sugars are evil” is the following: fruits, which are rich in sugars, are clearly health-promoting (see Harvard review)

Even the most vociferous anti-sugar advocates ‘concede’ this point (see Sugar Science FAQs and NY Times interview with Dr. Robert Lustig). Yet, a single large apple contains six teaspoons of sugar.

Clearly, sugar is NOT a toxin.

Indeed, every national and international report on sugar and health is crystal clear that we only need to worry about limiting our intake of “added sugars” or “free sugars” but NOT those found in fruits and veggies (and veggies, including the sweet ones). For example, the World Health Organization, Health Canada and the US national guidance.

Lesson 1: The dose (and source) make the toxin. Sugar can even be beneficial when consumed in moderation, in the context of whole fruit.

Is there any truth to “sugar is a toxin?”. Yes. There are some contexts in which excess sugar is clearly harmful.

This brings us to our first truth:

Truth 1: My liquid forms are your worst health foe.

Whereas eating sugars from whole fruits is associated with heath benefits, the opposite is true of sugars from sugar-laden beverages, including, in some cases fruit juice. In general, the more liquid sugar you consume, the greater your risk of type-2 diabetes, obesity, and the slew of related health outcomes. Check out the research for yourself here.

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Sugar-sweetened beverages are consistently singled-out as health foes in international and national reports on sugars and health. See the World Health Organization , Health Canada and the United States. These reports all hone in on sugar-sweetened beverages as your worst health foe.

Why are sugar-sweetened drinks public health enemy number one?

Research is still working to give us a clear answer but we have some solid theories. These drinks have several things going against them: 1) a double whammy of lots of sugar and zero fiber makes for a sharp blood-sugar spike; 2) the liquid form makes them easy to over-consume, which drives obesity (see Nature research article).

Lesson 2: Your best bang for your buck when it comes to reducing sugars comes from ditching sugar-sweetened beverages and other liquid forms that are easy to overeat.

This brings me to our next truth:

Truth 2: Eating less of me does NOT guarantee weight loss.

If sugar directly caused obesity, this is we would predict:

  1. People who eat more total sugar should be more likely to be overweight.
  2. People who reduce their intake of sugar should consistently lose weight.

Neither of these things are true.

Surprisingly, neither total sugar intake nor intake of added sugars are strongly linked to obesity. While this is true in some cases, there are plenty of exceptions, including Australia & Canada. In both cases, obesity rates climbed from the 1980s to early 2000s while added sugar consumption stayed flat or declined. These findings tell us that cutting sugar is not a cure-all and that HOW we eat our sugar matters greatly.

But…why did so many of my friends lose weight by cutting out sugars?

The prevailing theory is that sugars contribute to obesity by promoting overeating. Anyone with a sweet tooth, or any carb-o-holic knows this well. It is easy to find yourself eating more than you need because one bite leads to another, and another, and another. Those who find sugar and carbs to be a “trigger food” stand the most to gain by watching their intake.

This theory also explains why sugar-sweetened beverages seem to be particularly problematic. Liquids tend to be less satisfying (satiating) than their solid counterparts, which makes it easy to consume excess calories. Indeed, the number of excess calories that Americans consume matches their average intake of sugar-sweetened beverages very well (see Nature research article).

This theory is supported by studies of the effects of eliminating sugar, with and without reducing overall calories. We only see weight loss when we cut out the sugar AND the excess calories it was contributing. We do not see weight loss in studies where if the eliminated sugars are replaced with an equivalent number of calories from another source (e.g. whole grains). In science-speak, these are known as ‘isocaloric’ trials (see review article here) [].

Lesson 3: Cutting out sugars CAN help you lose weight, but only if you don’t replace the sugar calories with other foods. It is most likely to help if carbohydrates are a “trigger” for you.
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Truth 3: A spoonful of me causes LESS of a blood sugar spike than eating white bread.

To understand this one, let’s look at the three types of carbohydrates.

- The three main types of carbohydrates in our foods are starches, sugars, and fiber.
- All three types of carbs are made of the same three simple sugar units (glucose, fructose, galactose). They differ in how long the chains are, which units are linked together, and how.
- Most sugars are roughly half glucose and half fructose.
- Milk is the exception, it is made of half glucose and half galactose.
Note: Most artificial sweeteners and zero-calorie plant-based sweeteners (such as Stevia) are NOT carbohydrates.

We see a greater “blood sugar” rise when we consume starches than when we consume an equivalent amount of pure sugar. The shape of the rise is most dramatic with refined grains, which have been stripped of the fiber that would otherwise slow digestion.

Why? When we refer to ‘blood sugar’ we are really talking about levels of glucose in our blood. The fructose doesn’t count (at least not right away). The sugars in starches are 100% glucose, whereas those in sugars are 50% glucose and 50% fructose. Thus, for the same amount of total sugar, 100% of it will ‘register’ as sugar in our blood for starches, whereas only 50% ‘counts’ for sugars (e.g. fruits or sweeteners). This is why sweeteners that are higher in fructose and lower in glucose, such as agave, have a low ‘glycemic index’. Learn more from Harvard Health about glycemic index and glycemic load here.

Unlike glucose, our bodies cannot use fructose for energy ‘as is’. In order to make it usable, fructose travels from our gut to our liver, where it is transformed into other molecules, which can be used (or stored). For this reason, fructose doesn’t cause a spike in “blood sugar” (or insulin ).

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Is fructose a free ride for sugar lovers?

It might be tempting to think that fructose offers a free ride for sugar lovers, because it doesn’t trigger an intense insulin response. Indeed, the diabetic community embraced fructose several years ago, then quickly changed their tune. Fructose is NOT a free ride. Again, the story is complex and fructose may or may not be harmful depending on source, dose, and context.

Lesson 4: If avoiding blood sugar spikes is your goal, you get more “bang for your buck” by eliminating refined grains than sugars!

Note: Whole grains are also a healthy source of carbohydrates, despite their high glucose content. We will explore this another time — get a sneak preview of the research here []

Bottom Line

The bottom line is that it’s not as simple as “all carbs or all sugars are evil”.

By following some simple rules, you can include some sweetness in your life in a healthful way:

  • Satisfy your sweet tooth with fruits (and sweet veggies). Their high content of fiber, water, and other nutrients, makes them a net win.
  • Avoid sugar-sweetened beverages and liquid sugars, because they ‘whack’ your system hard and fast, and can fuel overeating.
  • Avoid refined grains, as they cause your blood sugar to spike even more than pure sugar!
  • Moderation, moderation, moderation. The dose (and context) make the toxin!

Last but not least, bear in mind that everyone’s tolerance for sugar varies. Listen to your body.

Your response to sugars depends on many factors, including the state of your energy regulation systems (e.g. insulin sensitivity), your gut microbiome, and how strongly sugars trigger your brain’s “do it again” signals. Some of these factors are strongly genetic, while others are environmental and can be tuned in your favour. Another topic for another time!

About me

I am formally trained in human genetics (PhD) and spent the first decade of my career working in cancer research, drug development, and personalized medicine.

This new chapter of my career is dedicated to helping others to live their healthiest lives. I strongly advocate for a plant-rich diet and love helping others learn to make #plantsmart choices.

For more nutritional insights — and healthy, simple, recipes , check out my website (Fueled by Science).