Sugar is Toxic

Toxic plateDid you know that sugar is toxic?

I have had this blog article brewing for about 3 years now and it all started with a New York Times article entitled Is Sugar Toxic? and a 90 minute video by Dr. Robert Lustig entitled Sugar: The Bitter Truth.

What is sugar?

“Sugar” commonly refers to sucrose, which is a molecule made of two parts: glucose and fructose.  When I refer to sugar in this article, I am referring to sucrose specifically.

Glucose vs. fructose

Glucose is referred to by Dr. Robert Lustig as the “energy of life” because it the primary form of fuel for all cells in the body to create energy.  Our bodies are highly efficient, so if there is any extra glucose left over when we eat, it is stored as glycogen in muscles and the liver.  Glucose is found in dietary carbohydrates, either on its own in starchy foods like grains, or combined with another molecule, as in sucrose (in sweet foods) or lactose (in dairy products).

Fructose is the other part of sucrose and it is quite different.  Fructose can only be metabolized in the liver and excess is converted into fat which is stored in the liver.  Ever heard of “fatty liver?” Excess intake and storage of fructose is one way that this comes about.  Fructose is far less useful as a fuel because it can’t be used by most of the body and it creates waste products which must be eliminated to maintain health.  These features make it more of a toxin!

Why is sugar so bad?

Diabetes warning road signThe root of chronic disease

Excess intake of sugar, delivering both glucose and fructose, is a major health issue facing society today.  Chronic use promotes obesity, diabetes, lipid imbalance, hypertension, cardiovascular disease, fatty liver disease, and many other chronic and deadly health concerns.  It is actually the fructose is particular that poses a massive problem.

Let’s dig a bit deeper into heart disease, which is the number two cause of death in Canada and number 1 cause of death in the United States.

According to a Globe and Mail article entitled Excess sugar can triple risk of dying of heart disease, people who get 25% or more of their calories from sugar have TRIPLE the risk of dying of heart disease and people who get 10-25% of their calories from sugar increase their risk of cardiovascular disease by 30%.  The top sources of sugar are soda, sports drinks, sweetened juices, desserts (baked goods, cake, cookies, etc), and candy.  Drinking an average of one sugar-sweetened beverage per day increases risk of dying of heart disease by 29% compared to drinking only one per week!

Signaling is key

Our bodies are complex systems that rely on signaling to direct activities to achieve optimal health.  It is these sophisticated and sensitive systems that maintain homeostasis (a fancy word for balance).

Sugar sends the wrong messages!

When we eat glucose, it suppresses ghrelin (a hormone that stimulates hunger) and stimulates insulin and leptin (hormones that tell you to stop eating).  This makes sense, since once we have enough glucose, we don’t need to eat any more until the next time we need energy!

Fructose once again is different.  It does not suppress ghrelin, nor does it stimulate insulin and leptin, so it doesn’t send the important signals that your body needs to know to stop eating.  This signal interruption over time causes major disruptions in healthy function, leading to chronic disease.

In his video, Dr. Robert Lustig goes into great details to explain the physiological mechanisms behind these effects, as well as examining the large volume of quality research data that exists linking sugar intake with disease.

How much is too much?


The World Health Organization recommends a maximum of 10% of daily calories from added sugar.  Less than 5% would be ideal.

According to a Globe and Mail article entitled Excess sugar can triple risk of dying of heart disease, 10% of adults consume more than 25% of calories from added sugar, while 72% consume 10-25% of calories from sugar.

How do you figure it out?  One way would be to track your food intake via an app like MyFitnessPal.  You can see how many calories you eat each day and calculate how many calories come from sugars by multiplying the grams of sugar by 4, which is the number of calories per gram of carbohydrates (which is what sugar is).  This figure will include all sources of sugar (even whole foods like grains, fruits, vegetables, etc) but it will give you a sense of how much sugar you are eating.

Added sugars are hard to separate out, but a good guideline is to avoid packaged foods and the use of sugar when preparing food in favour of natural forms of sugar from whole foods.

What about fruit?

When I talk to patients about sugar, this is a common question.  Yes, fruit contains sugar, but the effect on the body is quite different than sucrose!

Fruit is food, sugar is not!

Dr. Robert Lustig says in his video “when God made the poison, he packaged it with the antidote.”  Think about how you would find sugar in nature.  It is always accompanied by fibre as part of fruit or something like sugar cane.  Have you ever chewed on a sugar cane?  It takes a lot of work to get just a bit of sugar!  Fibre protects your body from a huge spike in sugar because it slows down absorption, in addition to being incredibly helpful in many other ways (but that is another blog topic).  Sugar in nature is also accompanied by many essential nutrients that support good health and help our bodies maintain proper signaling and homeostasis.

Whole foods contain sugar in much smaller quantities than many people are used to consuming unless they are processed, altered, and concentrated, as in the case of fruit juices and dried fruits.  It is much harder to overeat sugar in the form of fruit for these reasons.

Finally, fruit doesn’t have as much fructose as you might think.  Just because fructose has a similar name to fruit doesn’t mean it is found in the greatest abundance in fruit.  Check out the Sugar Content of Popular Sweetened Beverages and this list of Fructose in fruits, vegetables, nuts, seeds, legumes, and grains.  Combine these and here is a ranking of top foods high in fructose:

  • Raisins, 1 cup: 43g
  • Dried figs, 1 cup: 34g
  • Coke, 355mL can: 26g
  • Prunes, 1 cup: 22g
  • Dried apricots, 1 cup: 16g
  • Mango, 1 fruit: 16g
  • Miso, 1 cup: 16g
  • Unsweetened apple juice, 1 cup: 14g
  • Cabbage, 1 head: 12-13g
  • Grapes, 1 cup: 12g

Keep in mind that sweeteners like sucrose, honey, maple syrup, etc are not included on this list.  These are all high in fructose and would rank pretty high.

Watch your portions

It’s not surprising that dried fruit is high on the list, but also look at the serving size.  When was the last time you ate a whole cup of raisins?  Most people consume smaller servings of these foods and they are high in fibre and nutrients, so still a much better choice than a can of Coke.  It’s also interesting to note that miso (fermented soy) and cabbage rank so highly, although I don’t know anyone who is eating a whole head of cabbage…

Reality check

It’s easy to become accustomed to eating a lot of added sugar.  It’s everywhere!  In sweet foods as well as many foods you might never suspect!  Other people even encourage you to eat more sugar!

However, sugar is not necessary for enjoyment of life and in fact detracts from living a vibrant and fulfilling life by compromising your health.  Sugar is not a suitable reward or incentive and it is also not a right.  Our caveman ancestors had to work pretty hard to get sugar and even if it surrounds us now, you don’t have to eat it!  Anyone who has ever experiences a “sugar high” also knows that sugar is a drug and the sooner we treat it as such, the better off we will all be!


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