Thursday, January 20, 2011

Fructose, the not so innocent sugar

I've talked previously on the blog about sugar and how your body processes it.  Now I want to cover why Fructose, a specific type of sugar is particularly bad for you.  This all stems from the principal that all calories are not created equal when we are trying to fuel our body.  If you already subscribe to a Paleo/Primal lifesyle this concept probably makes sense to you.  If not you may assume that the key to weight loss and overall health related to Calories In - Calories Out , if you take in more calories than you burn you get fat, if you take in less calories or burn more calories than you take in, you lose fat.  A few "experts" on the all calories are not created equal subject are Gary Taubes who wrote "Good Calories, Bad Calories" and just released a new book which is a sequel to Good Calories, Bad Calories that is more digestible "Why we get Fat, and what to do about it" along with Dr. Robert Lustig whose lecture, Sugar: The Bitter Truth which was published on YouTube made a huge splash.

So losing fat isn't as easy as calories in being lower than calories out.  You need to take a look at what you're eating as well as how much.  As a nation Americans are getting fatter - on average we Americans weigh 25 more pounds than we did 25 years ago (~1985).  How are we gaining all this extra weight, beacause we're eating more and too much of the wrong stuff.  And the reason why we are eating more than we need, its because we are increastingly Leptin resistant. Leptin is the hormone that tells your brain that you are full and you don't need anymore food to fuel your body. When you are Leptin resistant, that means that your brain doesn't respond as well to the leptin signals, meaning that even though you have enough food for fuel your brain doesn't register that I'm full signal and you still feel hungry, so you eat more than you need. What causes the letpin resistance in your body - one thing is the processing of fructose in the liver. If you look at what the extra calories are in today's diet, it is generally in the form of added carbohydrates.  In the 1990s when the nation started following the high carbohydrate and low fat diet have essentially doomed ourselves to a diet that will make us fat through the increase in carbohydrates in our diets.
   Did you know that 1 soda a day (additional 150 calories) is an additoinal 15 pounds of fat per year that is added to your body.

Americans today eat/consume a whopping 141 pounds of sugar per year!

I've also already covered that eating fat doesn't make you fat, and told you that sugar is the culprit.  Do you find it at all ironic to think about what the food compaines do when they create low fat foods?  When the fat is removed from food, it compromises the taste and no longer tastes as good - so to make things taste better when food companies remove fat, they add carbohydrates in the form of added sugar.  They are removing fat, which people think makes them fat, and adding sugar which is what actually makes you fat.  One of the most common and least expensive sugars to add is High Fructose Corn Syrup (HFCS) found in most processed foods today.  It is actually sweeter than "sugar", regular table sugar (sucrose) has a sweetness value of 100 where HFCS has a sweetness value of 120.  For comparison sake, glucose has a value of 74 and Lactose (milk sugar) has a value of 15 - its not sweet at all.  You would think that food companies would use less HFCS since its sweeter, but instead they use the same amount since its so cheap and that leads to increased calories and increased sugar in your diet.

Don't believe the hype - the marketing campaign created to make people think HFCS is safe

What exactly is High Fructose Corn Syrup? High Fructose Corn Syrup = Glucose + Fructose molecule(s).  Looking at what its' made of: glucose can be used by your body as fuel and fructose = fruit sugar, so it can't be that bad, right?  If you think about it logically, naturally occuring fructose in fruit and vegetables is ok and your body can process it.  What you need to be worried about is all of the EXTRA fructose that is sneaking into you diet that is hidden in sugary drinks, juice, and HFCS that is added to most processed foods.  Fructose is unique because unlike glucose that can be used by almost every cell in your body to make energy, fructose can only be processed through your liver.  And your liver is only designed to handle a small amount of fructose everyday, so the addition of HFCS to the fructose you're naturally eating (in whole fruits and vegetable) lots of fructose creates a volume issue and makes your liver work overtime.  This goes for all foods that are high in Fructose, not just because of added HFCS which means that juice is included in that list even if it's 100% natural no added HFCS.  Juice is VERY high in sugar and particularly high in fructose - if you think about it one 8oz glass of orange juice takes multiple oranges to make lets say 4 or so.  Would you ever eat 4 oranges in the same amount of time that it takes you to drink the juice? And you're missing all of the fiber and that helps your body slow the bollust of fructose as it hits the liver so you are in essence just consuming the fruit's sugar. 
Ok so eating fructose in whole fruits and vegetables is ok, and the added sugars in processed foods are the things to really watch out for.  So where do you find all this HFCS - hamburger buns, ketchup, bread, bbq sauce, pretty much all packaged foods.  What do I mean by pacakged foods, any food that comes in a box, bag, container, bottle, or package.  

So how has the American diet evolved to include so much fructose, here is the breakdown of fructose consumption reflected over the past few decades.

     - Baseline: Naturally occuring fructose consumed through fruits and vegetables 15g/per day
     - Prior to WWII average fructose consumption between 16 - 24g/per day
     - Between 1977 and 1988 went up to 37g/per day (8% of total caloric intake)
       *Note: 1975 HFCS was introduced into our food system
     - 1994 Consumption is up to 54.7g/per day (10.2% of total caloric intake)
     - Today's adolescents intake is 72.8g/per day (12.1% of caloric intake!)
       *Note: Today 1 in 4 are of adolescents are overwight or obese

Ok so you can see the steady rise in fructose consumption, and you know that fructose can only be metabolized by the liver - and the larger the amount the more problems it creates.  So what exactly happens when you consume fructose?  Here's a little science on how your body breaks down gluose, ethanol and fructose - this is a recap from the detail in Dr. Robert Lustig's lecture on YouTube, Sugar: The Bitter Truth, and this is my attempt at a recap it so you can see the impact that fructose has on your body.

The point of this breakdown is to show that calories are not processed equally by the body and to show how fructose differs from glucose and what the rammificaitons are. So it matters what kind of calories you put in because your body breaks them down differently. Sorry to dissapoint all of you that thought calories in - calories out can equal weightloss without regarding what you are putting into your body.  Reading this will definately make you think twice about both fructose and alocohol!

How Fructose is metablolized by the body - 3 examples, directly from Dr. Robert Lustig's lecture Sugar: The Bitter Truth, of how your body breaks down glucose, ethanol, and sucrose or bread, alcohol, and orange juice.

120 calories of glucose (e.g., 2 pieces of white bread) Sugar: The Bitter Truth 45:01 - 80%, 96 calories is used as fuel for your body (glucose is the energy of life) and the remaining 20%, 24 calories goes to the liver to be processed.  So what happens to the 24 calaories in the liver. 
Liver turns the 24 calories int glucose 6 phosphate, takes a phospahse from ATP.  Glucose turns to glycogen - which is a non-toxic storage form of glucose and the goal of your body is to turn glucose into glycogen (there is no limit to the amount of glycogen that your liver can store) and into pyrovate the mitochondria of your cells to make ATP.  Some is burned an energy and then some may be left over as citrate.  The citrate is then turned to fat by your body's enzymes, specifically VLDL - very low density lipoprotein (bad) since this causes heart diesease and is a substrate for obesity.  You started with 24 calories and about .5 calories is turned into fat.  Your brain sees in insulin release and sends the signal that you are metabolizing your breakfast and you don't need to eat again yet.

120 Caloires of ethanol (alcohol) (e.g., shot of makers mark bourbon) Sugar: The Bitter Truth 50:55- 20%, 24 Calories goes to the stomach, intestines, kidney, muscles, brain and then 80%, 96 calories of ethanol hit the liver - here is why alcohol is a problem, since the load that hits the liver is 4x the amount that hits when you eat glucose
In the liver ethanol is converted to acidaldahyde (bad for you), the acidaldahyde is then turned into acitate which enters the cells mitochondria and is used to generate energy.  This process creates a lot of citrate (about double the amount of the amount that hits the liver when eating glucose).  The citrate is again truned to fat by your body's enzymes creating a lot of VLDL - which the liver tries to export out since fat build up in the liver is not good.  By product of this is Dyslipedemia, FFA - Free Fatty Acids which contributes to making your muscles insulin resistant.  Also creates an enzyme called Junk1, that is the bridge between metabolism and inflammation (and you know that you want to reduce inflammation, since inflammation = disease in your body).

120 Caloires of sucrose (glass of orange juice) Sugar: The Bitter Truth 56:27 - 60 calories are glucose, so 20%, 12 calories go to the liver and the remaining 80%, 48 are used by the body.
60 calories are fructose, and all fructose calories (60) go right to the liver, giving the total load to the liver of 72 calroies.
The process of adding a phosphate in the liver causes more things going on, creates a waste product of uric acid (a waste product that is goes out in your urine) which causes gout and reduces the production of nitric acid in your arteries which is something that allows your blood to flow freely through your arteries and will cause high blood pressure.  It also releases lots of fat storing enzymes and lots of citrate that is left over, which changes the fructose into lots of VLDL and directly into fat.

Fuctose also increases production of FFA - Free Fatty Acids that makes your muscles insulin resistance, which releases more insulin - and insulin is a storage hormone and its job is to take sugar and store it as fat.  And causes many other problems, like type 2 diabetes.

In conculsion, eating large amounts of fructose leads to the following chronic diseases:
     - Hypertension (High Blood Pressure)
     - Obesity
     - Fatty Liver
     - Insulin Resistance
     - CardioVascular Disease
     - Leptin resistence (no longer hear the "full" signal)

How much fructose should you be eating?  Your best bet is keeping consumption at the naturally occuring level, what is found in fruits and vegetables.   Dr. Lustig says that the correlation of fructose intake to declining health is 50g of fructose per day, once you exceed that limit fructose become toxic to your body because it overloads the liver.  Two things you can do to help mitgate the fructose load in your body, is to eat fiber (e.g. eat the whole fruit not drinking juice) which helps give the liver a break in the breakdwon of fructose and to exercise.  Exercising can metabolize fructose before it gets to your liver and is turned into fat.

How much is 50g/day, well its less than the amount of fructose in a 20oz soda.  And you may want to reconsider using Agave too since agave is pure fructose, stick to honey when you need a sweetener and you and your waist line will be better off.

Now that you know where fructose is in food, how to avoid it, what does that mean to you and your food choices. First I hope it makes your rethink the juice, sodas, and other sugar sweetened beverages - there is no reason to put your liver though that just for a sweet drink. I know this has made me think twice about how my body processes alcohol, one drink is already a volume issue so imagine how that is exemplified by 2, 3, and 4. Stick to eating whole fruits and veggies and you'll mitigate your fructose intake, just don't eat nothing but fruit or you'll be back in the danger zone hitting over 50mg per day.

Where to go for more information and to hear how fructose is metabolized explained again, I highly recommend you watch the You Tube video.

Sugar the Bitter Truth lecture by Robert H. Lustig, MD
Noteable sections: Breakdown of Fructose in your body 45:00, Juice 27:00, 56:51  Baby Formula 1:19:00

Jimmy Moore Living La Vida Low Carb Interview with Dr Robert H. Lustig


  1. I bet people would feel differently about sugar if they had to CARRY that 141 pounds with them wherever they go. Actually, the sad thing is that some people do!

  2. Fructose is sweet but dangerous. Too much intake of fructose might lead to serious liver problems.

  3. Great post, Laura! It is just mind-boggling to me the types of foods and the great number of products that they add HFCS to. It makes me sick when I read labels of foods at the store and see that HFCS is added to them. And the scary thing is, they are even adding HFCS to seemingly "healthier" foods. I even saw dried cherries at the store that had HFCS added to them. It's all about how much money these companies can save by manufacturing their products with cheap HFCS - and ultimately it leads to putting more green in their pocket.

  4. Hi Laura,
    Great post. Very thorough and clearly written.
    I would caution you that HFCS is not just one glu + one fru molecule. If that were true, I don't think we would be in such bad shape. Unlike sucrose, a disaccharide of fru and glu, HFCS is only a blend of fru and glu. This ratio, fru:glu can easily be manipulated. According to the CRA, HFCS-42, 42% fructose, is used for dairy and baked products. HFCS-55, 55% fructose, is used for soda and beverages. Now these ratios seem pretty close to the 50:50 of sucrose. (Though I am firm believer that HFCS-55 is metabolically different than sucrose). However, go to ADM's website. Their Cornsweet90 is 90% fructose. The intensely sweet Cornsweet 90 is used for low-cal products. In a recent paper by Keck Medical School at USC, Dr. Goran's team surveyed the %fructose in locally obtained soda. Three different national brands of bottled soda had 65% fructose. Could the CRA be manipulating the %fructose?
    In your article you stated that sucrose had a sweetness rating of 100 (the standard) and HFCS had a rating of 120. I find that very interesting, because if you go back and look at the original literature on HFCS, HFCS-42 was given a rating of 100. Now if you go to the CRA website, they say that HFCS-55 has a rating of 100. The difference between HFCS-42 and HFCS-55 is 30% more fructose. Have our tongues been that jaded by this industrial sweetener, or is the CRA fibbing?
    Personally, I think that HFCS-42 is probably as sweet as sucrose, and they have jacked up the %fructose in the sweetener so the end manufacturers can use less.
    Unfortunately, our livers have taken the hit.
    Take care,
    Cynthia Papierniak, M.S.

  5. @Cynthia, thanks for the detailed information - I'll update the post to reflect that HFCS is glucose & fructose, but remove the 1 to 1 relationship.