Fructose – The Natural Born Killer. Fact Or Fiction.

To eat fruit or not to eat fruit?

Is fructose evil?

What is HFCS?

Who is Agave and what does he want with my muffins?

If you Google ‘fructose’ you will be overwhelmed with articles debating whether fructose (or even sugar in general) is actually the spawn of Satan.

So what is all the fuss about?  Is sugar really evil? Am I not allowed to eat fruit anymore?  And if fructose is bad, then what is the healthiest sweetener to use in my recipes?

As per usual, I slipped into GEEK MODE and did some research as well as a quick sugar experiment, so we can all finally sleep tonight.


photo credit: ShellyS via photopin cc


Like Dr Karl, I like to run my own science experiments.  The other day I purchased a bag of refined sugary lollies and some Maltesers (GASP!).  Now as you might gather, I rarely indulge in processed sweet foods (or even processed food for that matter) as I prefer to avoid eating things that are costly and that make me feel like shit.  Go figure!

Playing the part of Dr Jekyl, I had two handfuls of the sugary confectionary.  I confess I was only going to have one handful, but after the first I turned into a drooling, greedy Mr Hyde (complete with a hunch back and limp) and I just HAD to have another handful.

mr hyde

Mr Hyde – GIVE ME MORE!!!!!

Regaining my composure as Dr Jekyll, I proceeded to try to hit the books for some serious study time. For the first 15 minutes, I felt fine.  Energetic even.  But then I crashed  and experienced a host of negative symptoms.  Mr Hyde was back with a vengeance… Here are the symptoms that I experienced:

  • Fluctuating energy
  • Lack of focus and concentration
  • Cravings
  • Tiredness  (I could hardly keep my eyes open)
  • When I woke from a 10 minute kip, I felt like I had a hangover
  • Brain fog (to the point I took nearly a minute to respond to the question “What is your name?” Yes…seriously!)
  • Bad taste in my mouth, like someone had died in it
  • Irritability (my poor husband…eek!)
  • Anxiety (And I mean heart-gripping-blood-racing-mind-firing-on-all-worry-cylinders-anxiety!)
  • Adrenalin
  • Insomnia

Could sugar really make you feel and act like this?

Whilst I realise this experiment is somewhat lacking in validity due to a lack of control, repetition and oh-so-many  potential variables, I would still like to wager that if I hadn’t eaten the sugary crap, I wouldn’t have had such negative health outcomes.  Don’t believe sugar can do this?  Cut out sugar for 3 months, then conduct the same experiment and tell me how you feel.

So what exactly about sugar could cause me to feel like this and how?


Sugar. Pretty, but deadly…                                                          photo credit: Swamibu via photopin cc


  1. Glucose a monosaccharide (mono = 1 sugar unit).  Glucose is easily broken down by all cells in the body and is the main fuel that our body uses for energy
  2. Fructose another monosaccharide (again…its 1 sugar unit) of which needs to be converted back to glucose for the body to be able to utilise it for energy.  It is found naturally in fruit, some grains, honey and some root vegetables.
  3. Sucrose a disaccharide (di = 2 sugar units as they are literally 2 monosaccharide sugar molecules bonded together), a glucose bonded to a fructose.  Sucrose (aka table sugar) is actually 50% fructose and 50% glucose and is found naturally in beet/cane sugar and is commercially added to many processed foods.
  4. And then, we have a manufactured sugar called High Fructose Corn Syrup (HFCS).  HFCS is manufactured by converting the glucose derived from the starch found in corn, and is approximately 45% glucose, 55% fructose.  It is actually sweeter than sucrose (Oh goodie, just what we need!) and is also added to many processed foods.


Up until 1976 the main sweetener in food and beverages in the U.S was sucrose (table sugar).  Around 1974, due to fluctuating markets, sucrose supply costs increased and HFCS literally flooded the food and beverage market with companies altering their ingredients to substitute for the low cost HFCS.  This resulted in a substantial increase in HFCS usage of more than 1000% between 1970-2000’s.

In Australia however, sucrose is still cheaper than HFCS and is therefore still used in most food and beverages made here.  But that doesn’t mean we are free from it completely (i.e. imported goods), nor that we are free from over consuming fructose itself.

Historically, Westernised diets included an average intake of 16–20 grams of fructose, largely from fresh fruits per day.  By 2005, with the widespread use of HFCS in commonly consumed products, our added fructose daily intake increased to 85–100 grams. 

So it appears that the potential problem may not lie simply in whether we consume HFCS as widely stated on the internet, but rather HOW MUCH FRUCTOSE we consume in total and remember, thats including fructose from natural fruit, from HFCS and from sucrose, which is actually 50% fructose.

So why is there such a hype about fructose?  Fructose and sucrose, unlike HFCS, is natural, right? So whats the big deal? I’m glad you asked, let’s have a look…


To understand the sugar debate we need to have a closer look at the metabolic fate of glucose and fructose, that is, the way the body processes and uses both.

When you stuff your face with a handful of sugary M&M’s, glucose floods the blood and travels to the brain to supply it with energy.  It also stimulates the pancreas to produce the hormone insulin.  Insulin is like the sugar gate keeper; it regulates the glucose that is in the blood and decides whether it is going to store it, burn it or turn it into fat by stimulating De Novo Lipogenesis (DNL).

Under the watchful eye of our gate keeper insulin, excess glucose is converted into glycogen (the storage form of glucose) in the liver via a process called Glycogenesis.  The liver can store an unlimited amount of glycogen.

Insulin (which I am starting to think is more powerful than God) is the prime regulator of an appetite-suppressing hormone called leptin.  Insulin works synergistically with leptin to tell the body “YO stop eating dude, we are getting flooded with sugar and I need to deal with it all before we get overrun.”  And so leptin  sends a signal to your brain that you are NOT hungry and so you STOP eating.

Now in contrast to glucose, fructose cannot be used by every cell in the body as it is, but instead travels to the liver to be metabolised.   In fact, it is poorly absorbed in the gut and therefore reaches the liver almost completely intact. Unlike glucose, it DOES NOT stimulate the release of insulin.  Without insulin there is no release of leptin, which is the brain’s attempt to signal the body that it is full (meaning our body keeps thinking that we are hungry).

Fructose metabolises to fat in your body more quickly than any other sugar.  Whilst the body will think about what it wants to do with glucose (burn, store or make fat), the body WON’T need to make that decision for fructose – it’s straight to your hips baby!


So should you avoid fruit for the rest of your life to avoid any negative outcomes? I would say that’s a bit extreme.  

There are always two sides to every story.  Below are just some of the interesting arguments that I have taken from reading through the tonnes of data out there.


Fructose can convert to glucose provided we need the energy, but most of us aren’t energy depleted so its highly likely this won’t occur.


The fat produced in the liver due to fructose metabolism can lead to non-alcoholic fatty liver which can then lead to liver insulin resistance and type 2 diabetes.  Further, fatty liver causes the release of fatty acids into the bloodstream, which can cause muscle tissues to develop insulin resistance. One site states “fructose in sweeteners has now surpassed alcohol as the major source of liver disease”.


According to one study comparing the effects of fructose to glucose,  fructose caused more weight gain in the belly fat region, of which is associated with a higher risk of heart attack and stroke. “The fructose group also had higher total cholesterol and LDL (“bad”) cholesterol, and greater insulin resistance.” Fructose induced hypertension is not well understood, but it is thought that the involvement of high uric acid production, along with excess insulin are part of the problem.


High levels of blood glucose react with proteins to produce something called – advanced glycation endproducts (AGE).  These guys can cause inflammation, loss of tissue elasticity causing tissue stiffness and increased blood pressure. 

Now our friend fructose is more chemically reactive than glucose, not only producing MORE of these AGE inflammatory compounds, but producing them MORE THAN 10 TIMES FASTER.


Because fructose is taken up by the liver and therefore does not increase blood sugar or insulin the way other sugars do, fructose was once thought of as good for diabetics. 

Why is fructose a bad sweetener for diabetics? Eating fructose raises fructose levels in the blood which means production of AGE (that we touched on above), creating inflammation BUT ALSO because it doesn’t alert the body via insulin and leptin that it has just been fed and therefore, the body thinks it still needs food and the person keeps eating.


Fructose in the liver requires an enzyme (called fructokinase) to metabolise it and an indirect byproduct of this process is uric acid. A build up of uric acid has been known to cause goutcrystal-like deposits of uric acid in joints, similar to arthritis.

But wait, theres more… you also get a free pair of steak knives!  No, not really,  BUT with the increase of uric acid, nitric oxide (a blood pressure regulator) is blocked which means your arteries can’t properly dilate to allow blood to flow freely, creating more work for your heart and hypertension.


Now all of this is not sounding so good, but we need to take into consideration that the majority of studies that exist on fructose are on rodents, not on humans and are often using excessive doses as compared to what a human would actually consume.  

Also its worth pointing out that in our diet fructose is nearly always partnered with glucose (remember sucrose = glucose + fructose).  But, most of the fructose studies undertaken use massive doses of pure fructose alone, which is not representative of the typical diet.

But does mean that these health risks are incorrect?  I know that skinny jeans look bad on me, and I don’t need anyone to prove it to me.  You decide…


The anti-fructose camp argues that fructose will stimulate DNL (fat making process) to raise triglycerides leading to weight gain, obesity and metabolic syndrome.  And it has been found that when consuming HIGH levels of fructose our metabolism does veer towards fat storage.  Therefore, fructose CAN contribute to obesity through lack of communication with our brain to say that we are full, but ALSO by causing the body to burn sugar as opposed to the fat cells.

BUT…there are a plethora of studies out there that state that the amount of DNL in response to fructose, is minimal.  According to Dr. John Sievenpiper, M.D., of St. Michael’s Hospital in Toronto and author of three leading research studies on fructose  “…with a fructose load 50 percent goes to glucose, about 25 percent goes to lactate, greater than 15 percent and up goes to glycogen, the remainder would be oxidised directly [going to CO2 through the TCA cycle], and a small portion contributed to de novo lipogenesis.”  

So only a very small percent, like 10% of fructose actually contributes to the fat making process.  In the scheme of things, that really isn’t that much, so that one piece of fruit a day is not going to turn you into a heifer.


Another factor in the obesity and weight gain debate that is often neglected is that consuming beverages i.e. sugary soft drinks or fruit juice, can lead to unintentional overeating, not just through the lack of leptin response but because people consuming these drinks tend to forget to factor these beverages into their caloric intake for the day.  Just because it is a liquid and doesn’t require chewing does not mean that it wont impact your waistline.

Now if you have read my article on calories, you will know it’s not all about calories, but the bottom line is simple, if you constantly consume an excess of calories, be it by fruit, Twinkies OR soft drinks, you will get fat.


Fructose is thought to ‘light up’ the reward center of the brain, but after repeated exposure the sensitivity is somewhat lessened so that you need more to achieve the same effect.  Kind of reminds me of the plant, in the Little Shop of Horrors…”Feed me Seymour, feed me!”.  

Fructose has been assimilated in numerous articles to “alcohol” because the body treats its similarly to ethanol and has a similar addictive quality.

feed me seymour

Feed Me Seymour! Only this plant didn’t want fructose…


Although most cells can’t metabolise fructose as an energy source, cancer cells thrive on sugar and proliferate very well with fructose as their energy source.  Do you want to feed cancer cells?  Then grab a can of soft drink.


Sugar can interfere with your absorption of protein and disrupts the transfer of amino acids to muscle tissue, meaning that you won’t end up super buff, like our good friend Arnie (remember him from the grains article?).


Polycystic ovary syndrome (PCOS) is a condition caused by hormonal imbalances that cause symptoms such as cysts in your ovaries, an over production of the male hormone testosterone which can cause irregular ovulation or anovulation. A raised level of insulin in the blood is one of the underlying reasons why PCOS develops, causing the ovaries to make too much testosterone.  A high level of insulin AND testosterone interferes with the normal development of follicles in the ovaries and as a result many follicles can develop irregularly causing problems with ovulation – hence, period problems and even reduced fertility.


Now this one goes out to all of the folks that suffer from anxiety like me.  The anxiety that I experienced in my sugar experiment was the most intense I had suffered in months.  I have been told time and time again, just choose NOT to be anxious; divert the mind, meditate and CHOOSE to be calm.  Yeah right, that might get you so far, but when your mind is like a train on tracks that only lead one way, you can be sure you are going to end up at its final destination: Anxiety City – Population…YOU! 

Sugar stimulates a physiological stress reaction that stimulates adrenaline (hence the feeling I was taking a boxing class in the middle of my sleep).  And the adrenaline, stimulates cortisol (the stress hormone) release.  Think about it, the brain requires a constant supply of glucose and if you flood it, then take it away suddenly, and then flood it again…would you be a happy brain?

Of course there are other factors involved in anxiety, not just sugar. 


Chromium is a mineral that is required for insulin to bind to its receptor and to do its job properly.  Without chromium, insulin will NOT remove sugar from the blood and amino acids (building blocks of protein) FAIL to enter cells, LDL cholesterol and triglycerides increase and your immune system function is impaired.

Foods that stimulate insulin (hello…pasta, bread, cereals and soft drinks!) cause an increase in urinary losses of chromium, with fructose and glucose being the worst offenders.  So the MORE sugar and crap you eat, the MORE chromium you wee out, the LESS insulin will be able to do its job.


I touched on FODMAPS once before HERE.  FODMAPS is a reaction to certain carbohydrates that ferment in the gut, resulting in symptoms similar to IBS such as gas, bloating, cramps and diarrhoea.   Malabsoprtion of fructose and lactose can be an issue as well as carbs found in wheat, legumes and grains. 


What are the high fructose foods you ask?  Well for your convenience, I have compiled a list of the total fructose in fruit and sweeteners in foods from an Australian database.  

To make this clear, I am NOT advising anyone to avoid fruit.  I am simply providing you with the information to make educated decisions on your food choices.  Should you have insulin or blood sugar problems, fructose reactions, then by all means limit your fructose consumption (and remember, fructose also comes from sucrose…table sugar and processed food!). 

fructose table master

Table sources:
* USDA Nutrient Database


If you are numbers challenged (like I am), the table above means the fruits that are lowest in fructose are:

  • Avocado
  • Lemon
  • Apricots
  • Berries
  • Watermelon


On the other hand, the high fructose fruits:

  • Apples
  • Pears
  • Mango
  • Banana
  • Grapes
  • And…dried fruits (apricots, dates)


photo credit: Danilo Prates via photopin cc



  • Agave Syrup – I have heard agave syrup described  “like HFCS on steroids”.  It is 90% fructose
  • Sucrose (Table Sugar) – 50% fructose (but partnered with glucose)
  • HFCS – Artificial-Fructose-City…avoid at all costs
  • Artificial Sweeteners – sucralose, aspartame, saccharin.  The jury is out on these guys but they apparently can increase insulin production and contribute to hunger.  So until I have long term, irrefutable evidence saying they are a-ok without any negative impact, I will pass thanks
  • Coconut Sugar – from a coconut palm tree (not to be mistaken with a palm tree that palm oil comes from), has high nutritional benefit BUT still contains high sucrose and therefore fructose so should be used sparingly


Remember, context and dosage needs to be considered for all sweeteners as they can still raise your insulin levels.

  • Rice Malt Syrup – no fructose and no AGE reaction, but still contains glucose (although this is a processed product that is not considered paleo – if you care!)
  • Stevia – if you can fathom the taste, is a natural sweetener with no fructose
  • Dextrose Powder – glucose powder.  Whilst free from fructose, insulin still spikes resulting in cravings and hunger
  • Liquid Glucose – better than other sweeteners laden with fructose, but still elevates blood sugar and has potential AGE reactions 
  • Pure Maple Syrup – refined sap from maple trees, is low in free fructose but high in sucrose.  However, it does offer iron, calcium and manganese
  • Raw Honey –  still contains fructose, but I think small amounts of raw honey are acceptable for its antioxidant and antibacterial properties and due to studies showing that honey when compared to fructose, increases vitamin E and DOES NOT raise triglycerides. But only consume RAW, not the processed crap 

Interestingly, there are theories that a tablespoon of raw honey can aid in better sleep. This is thought due to honey being half glucose and half fructose; glucose enters the blood quickly, supplying the brain in the first half of the night, with fructose turning into glucose (provided you haven’t gorged on sugar throughout your day) slowly, meaning your body has a steady supply of energy the entire night. Read more here.

Want more information on the fructose debate?

Watch this famous video by Dr Robert Lustig who delves into the science behind the fructose debate. Or perhaps you want the other side of the debate? Check out here, here and here.

fruit lady

All sugar in moderation, no matter how tempting…


Dose and context are important in the fructose and sugar debate.  Excess fructose, just like excess sugar, just like excess carbs, are bad for you.  Point blank.  

Do I eat fruit?  Yes I do. I LOVE fruit, especially peaches and berries.  But again, I don’t overindulge.

Should you avoid fruit?  That is entirely up to you and your state of health.  If you feel you eat too much fruit, then moderate it.  If you feel you can’t eat fruit due to FODMAPS or you have a sugar addiction, then cut it out for a month and see how you feel.

What it really comes down to is controlling your insulin.  Moderate foods that make your insulin spike and avoid PUFAs, such as vegetable and seed oils (sunflower, safflower, soybean and canola) that interfere with glucose uptake in cells (more on that soon!)

Whether you want to buy in to the fructose debate and get hit like a piñata by the science or not, it really is quite simple…

  • Only eat Real Food

  • Keep all forms of sugar to a minimum

  • Don’t over indulge

What sweeteners do you prefer and why?  Do you experience any of the health issues associated with sugar, mentioned above? And what do you think about artificial sweeteners?  

Coming Soon!! PART II:  How to Get Real and balance insulin and blood sugar

Sources: *All references are hyperlinked in this article.

Cover Image: photo credit: Jeanny Schmidt via photopin cc

17 Thoughts on “Fructose – The Natural Born Killer. Fact Or Fiction.

  1. I have battled with the side effects of high and low blood sugar for most of my life, but I am not diabetic. What you have written makes a lot of sense to me. I know I need to cut out the sugar, but I struggle to say no sometimes. I would love to have a few tips on how I can beat it.

    • Nicole - The GRL on November 28, 2013 at 5:19 am said:

      I think a lot of us struggle with highs and lows. An upcoming post (part II) will be focusing on exactly that. I think we all have much to learn about insulin – I can’t wait to delve into it further! Thanks for reading Rick.

  2. Do you have any ideas where to buy the sweeteners cheaply in Australia? I have seen various brands at health food shops, but they are so expensive. Can you get them in bulk? Thanks!

    • Nicole - The GRL on November 28, 2013 at 5:16 am said:

      Hi Sarah, I am working on building a solid network of contacts to provide the best and cheapest health products. Stay with me, I hope to get it out soon! Have a great day.

  3. laura dube on November 25, 2013 at 10:24 am said:

    Great read. I Love how you write. It is comical.

  4. I am very sad to read this. You mention that most people have enough energy through other food – what is this other food? It is unacceptable and egocentric to assume everyone gets enough energy through other foods therefore they dont require fructose? Your experiment and research is flawed based on this, you cannot comment on how much energy most people consume because you do not know this. Fruit is natures gift to people and it sickens me to think how many young people will be poorly influenced to avoid fruit based on your very flawed comments and hypothesis. Fruit is good for you, processed foods are not good for you.

    • Nicole - The GRL on November 28, 2013 at 4:39 am said:

      Hi Amy,
      Thank you for reading and thank you for commenting. Firstly I have to ask you to please read all of the article, and not just skim read before commenting as you have missed vital information. I have stated in my article “should you avoid fruit for the rest of your life to avoid any negative outcomes? I would say that’s a bit extreme.” And I go on to say that I eat fruit. It is fructose from sucrose and refined sugar and sweeteners that I am warning people about, and over consuming fruit IF you have blood sugar problems.
      In terms of energy – if you read my article in its entirety, I have also stated “Dose and CONTEXT are important in the fructose and sugar debate.”
      In case I have somehow left my opinion on the fructose matter unclear, I have added a sentence under the heading “fructose in food” that should make this clearer.
      Thank you for your comments.

  5. Amy, if a person is overweight and wants to drop a few kilos then it’s a good idea to cut back on fruit intake. Yes fruit is full of vitamins and minerals but it’s also high in sugar apart from berries etc. Why not increase intake of vegetables instead as they are also packed with vitamins and minerals, full of fibre and got bugger all sugar. One can easily thrive on eating fish, meat, eggs, nuts and vegetables.
    Obviously if a person is training hard in any sport and their weight is not an issue then fruit intake is probably not something that needs be addressed.

  6. thx for the article.

    btw, dextrose is just another name for glucose, so dextrose powder is glucose powder

    • Nicole - The GRL on January 14, 2014 at 2:37 am said:

      Hi Daz, Thanks for reading. Did I mention dextrose powder in my article? I couldn’t see any reference to dextrose powder?

      • yep, it was under the ‘THESE ARE OK:’ heading

        • Nicole - The GRL on February 4, 2014 at 1:37 am said:

          Hi Daz, Ah…cheers, I’m up to my eyeballs in research and didn’t have time to locate. I have listed dextrose in the ok section, purely because the lack of fructose. Its really not an absolute yes and no list, but I have tried to base my suggestions on getting minimal fructose. Plus, I think a lot of athletes like dextrose powder for fast glucose replenishment to muscles.
          But to clear up any possible confusion, I will make a note next to the naming so people are clear that its another form of glucose.
          *You might need to become my editor and science checker-upper-er ; )

          • :)

            i guess my point was that you listed ‘dextrose powder’ & then listed ‘glucose’ in the line below…
            afaik, dextrose is Not another ‘form’ of glucose, it is just another ‘name’ for glucose (dextrose Is glucose).

            i always took dextrose to be an American term. ie. Australian packaging usually reads glucose powder (i am in Australia as well).


  7. “…there are studies that show a tablespoon of raw honey can aid in better sleep. This is due to honey being half glucose and half fructose; glucose enters the blood quickly, supplying the brain in the first half of the night, with fructose turning into glucose (provided you haven’t gorged on sugar throughout your day) slowly, meaning your body has a steady supply of energy the entire night”

    Hi again Nicole,

    i was just reading about the Honey before bed ‘thing’ again…
    re. the text above, were you linked to Seth’s site, i think this was just a possible explanation (theory/hypothesis) put forward by Seth…?

    But if you do have any links to studies that cover some (or all) of these points i would love to read them.


    • Nicole - The GRL on February 4, 2014 at 1:09 am said:

      I stand (or sit in this case) corrected. I should have said “There are suggestions that ….” In this instance, it was not a peer reviewed article unfortunately. There are studies on honey in relation to sleep, but they are more focused on stopping coughing in children, hence the rested sleep. I will update. Thanks for the pick up.

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