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Fructose is not Glucose, it is a poison

I just got through watching this video which you must see (or you can read my summary below).  The video is a speech done by Robert H. Lustig, MD, UCSF Professor of Pediatrics in the Division of Endocrinology where he exposes the truth behind why we are so fat (it ‘s no longer just you North America, the world has decided not to leave you alone in this).

Before watching this video I always believed that the best way to lose fat is by the  first law in thermodynamics (take the dust off those old chemistry notebooks) that states that  the energy in a closed system is always constant.  In human that would be that what ever you eat, you better burn, or else you will store it.  This leads to thinking that we need to exercise to burn the pizza and cheese cake that you had for lunch.  Unfortunately or fortunately this isn’t true. Why? Because a calorie is not just a calorie.

It is believed that obesity is the relationship between genetics and our environment.  Science has discovered that our genetic pool has not changed over the last couple hundreds of years, but our environment has, and a lot.  Technology has changed our life in every aspect: in how we communicate, work, and eat.  All it takes is a glance at the ingredients of any box or jar in your house, and I bet you will discover things people 200 years ago would be like, “what the heck is that? You eat that stuff?”

Back to the good stuff.

If you plan to store energy and expect to burn it, normal energy expenditure for normal quality of life, which is the same, because everything that helps burn calories or increase our energy expenditure makes us feel good.  That’s why people are addicted to coffee or ephedrine (off the shelves now), and the same is true for the opposite; everything that causes us to spend less energy makes us feel lousy (i.e starvation, hyperthyroidism).  So, if you plan to store it you and you expect to burn it, then you have to eat it.  This turns the calories in and calories out into secondary processes in comparison to the storing process which is primary.  This turns the obese person into a victim, which is probably how you feel.

Recent studies have shown that people nowadays consume more calories (275 calories to be more exact) that what they did before. Why? It is not because they burn more calories, or because they have bigger stomachs.  It is because something is wrong with the signal that is supposed to tell your brain to stop eating.  The messenger is being killed somewhere along the way and the message isn’t getting through.

The messenger is a hormone I have mentioned before called leptin.  Leptin is in charge of regulating the amount of food that we eat so that we can burn calories efficiently.  When people are eating for than what they should and gaining weight is because something is wrong with their leptin. A question that arises is where are those extra calories coming from?  Some people believe it is from the fat but that isn’t true… it’s from the carbs.  So why are there low fat foods and not low carb foods?

“The Fat is going down, the sugar is going up, and we are all getting sick.” Robert H Lustig

It all began in 1982 when we were warned by scientist and the government that eating fat increased our Low Density Lipids (LDL’s) which various studies linked to heart disease.  They recommended we drop our fat intake from 40% to 30%, which we did, but we didn’t get thinner, why? Well because of the carbs. We started to eat a lot more carbs.  Since saturated fats were demonized (read here why that isn’t true), everybody started eating low fat foods.  Fat plays an important role in taste and foods with low fat content are not palatable to us, so what do food companies do so that we eat their low fat food… they put sugar in it, and not just any sugar, they use High Fructose Corn Syrup (HFCS).  HFCS is a glucose molecule linked to a  fructose molecule, which makes HFCS is sweeter than sucrose (table sugar).  Since it is sweeter you would expect that we eat less of it… wrong, we eat more.

(Watch the video around minute 13:30 to learn about the Coca Cola Conspiracy).

Why is High Fructose Corn Syrup so bad?

Get ready for some Biochemistry. Pay attention because this is why fructose is not like glucose, like you are meant to believe.

1. Fructose does not suppress ghrelin, which is a hormone that stimulates hunger.

2. Does not stimulate insulin (you would think this is good, but it isn’t).

3. Hepatic fructose metabolism is different.

4. Chronic fructose exposure produces metabolic syndrome.

Watch the video because he explains it a lot better than me. (Go to minute 45).

Lets see how glucose is used by our body. Glucose is the energy that makes life.  Every living thing uses glucose as energy.  Taking this into account our body uses 80% of our ingested glucose to feed every cell and organ.  The remaining 20% hit the liver, and this happens…

Glucose Metabolism

Lets make believe you just ate 120 kcal (2 slices of bread). Glucose stimulates the pancreas to produce insulin; insulin then binds to its receptor and takes the substrate IRS-1 (not important) and it is going to tyrosine phosphorylate  (big words) it which now activates pTyrs-IRS1, which in turn stimulates the Akt receptor; this guy then stimulates SREBP1 (this guy is responsible for getting fat mechanics going) the enzyme called glucokinasa which  phosphorylates glucose and turns it into glucose-6-p.

Now glucose-6-p can’t get out of the liver; the only way is with the help of hormones i.e epinephrine and glucagon.  Most of glucose-6-p is then turned into glycogen which is the storage form of glucose.  Now your liver can hold an infinite amount of glycogen without going into liver failure (check out von Gierke’s disease). The rest of the glucose-6-p is then metabolized into pyruvate which enters the mitochondria turns into Acetyl-CoA, which enters the Krebs cycle and produces ATP, the energy of life.

Now not all the Acetyl-CoA may enter the Kreps Cycle, some of it may exit the mitochondria in the form of citrate.  Citrate is the broken down by three enzymes that are the ones responsible for creating fat ( de novo lipo genesis), more specifically vLDL. vLDL is bad because it causes heart disease and is a substrate for obesity.  When your brain detects vLDL it tells you to stop eating>>>> this is good, this is supposed to happen.

Alcohol Metabolism

Now lets talk about alcohol or ethanol to be more exact.  Ethanol is a carbohydrate, but we all know that it is poison, it is a toxin.  We all know it can be bad for you, but it can also be good, but lets talk about why it is bad.

You have gotten wasted once or twice before in your life, and you have probably felt some of these symptoms:

1. CNS depression.

2. Hypothermia

3. Tachycardia

4. Vasodilation, decrease in BP.

5. Diuresis

6. Respiratory depression, etc.

In other words, if you been to college you know what I’m talking about.

On the other had fructose does none of this, why? Because the brain doesn’t metabolize fructose.  Thus fructose is not an acute toxin, and ethanol is.

Lets take a shot of liquor that has 120 kcal; 20% will be used by brain, kidneys, muscles, stomach, intestine, etc.  This leaves us 96 kcal going to the liver; that is 4 times more than the 2 slices of bread.

The ethanol go straight into the liver, it has no receptor, and is metabolized into acetaldehyde (cross links proteins which eventually leads to cirrhosis), which is then metabolized into acetate that enters the mitochondria (just like the pyruvate) it produces ATP, and it produces a whole lot of citrate (because more calories have gone in the liver).  All this citrate is going to be metabolized into vLDL.  All this vLDL is what causes the dyslipedimia of alcoholics.  The liver is going to want to get rid of all this fat, so it is going to great triglycerides and fatty acids which will be taken in by the muscles and produce something called insulin resistance, which is something you don’t want (causes diabetes).  Some of the acetyl-CoA won’t be able to leave the liver, and will end up precipitating and creating a droplet or a spot on your liver.  This excess acetyl-CoA also produces a enzyme called JNK1 which produces inflammation; this is something also produced by fructose which I will start to talk about now.

Fructose Metabolism

Fructose tastes good; this is why we have it in everything i.e ketchup, pretzels, bread, orange juice. Lets make believe we just ate 120 kcal of sucrose which is equal to a glass of orange juice.  So uptil now we have had 2 slices of bread, a shot of alcohol, and orange juice, all 120 kcal three different substrates.  Sucrose is made up of one molecule of glucose and one of fructose.

60 of the 120 kcal belong to glucose; out of those 60, 12 go in the liver, and the other 48 go to the rest of the body.  On the other hand all 60 kcal of fructose are metabolized by the liver because only the liver can metabolize fructose.  So what do we call a foreign substance to your body that can only be metabolized by your liver and once inside causes various problems? A POISON.

Fructose enters the liver just like glucose does, by the receptor Glut5.  Fructose is then metabolized by an enzyme called fructokinasa and turned into Fructose-1-P.  Before we had 24 kcal that had to be phosphorylated now we have 72 kcal (3 times the volume); this means we need a lot of phosphate.  Our liver has a scavenger enzyme that goes searching or phosphate called AMP deaminase.  This enzyme turns ADP to AMP to IMP and finally to the waste product Uric acid.  Uric acid is what we eliminate when we take a piss; it is also responsible for producing gout and hypertension.  How?  Uric acid blocks the enzyme that produces Nitic oxide (NO) which is responsible for lowering blood pressure; so if you can’t produce NO then your blood pressure goes up.  You know what is the first factor of death in the world? High Blood pressure, the cause, too much sugar in our diet.

Back to the Fructose-1-P.

The Fructose-1-p is metabolized into pyruvate which enters the mitochondria to produce ATP and citrate. The thing is that fructose does something that glucose doesn’t which is produce Xylulose-5-p (in orange in the diagram above).  For athletes this is good, because it helps replenish glycogen faster than glucose.  For athletes glucose makes sense, the problem is sports drinks are consumed by kids not by athletes.  Why? because it is cool?  Ok so why is Xylulose-5-P important? Because it is a precursor for three fat building enzymes i.e ACL, ACC, and FAS.  Ok, so now we have lots of citrate which turns into VLDL, that turns into triglycerides and fatty acids which eventually cause dyslipidemia.  In conclusion, eating fructose is like eating fat not a carbohydrate (watch the video around 1:03 for more evidence of this).

Not done yet.

Remember JNK1.  Well JNK 1 serine phosphates IRS 1 which prevents insulin to go in the liver.  If you remember from the glucose diagram IRS 1 was responsible for letting insulin in the liver, so now we have liver insulin resistance.  This causes the pancreas to produce more insulin, which raises blood pressure, causes more fat making, and makes more energy go into the fat cells (hello obesity).  Studies have also shown that high insulin levels blind your brain from receiving leptin (remember that hormone that tells you to stop eating).   In other words fructose tricks your brain into believing that your always hungry, so you keep eating and eating.

Now if we compare the long term effects of alcohol and fructose we get this:

8 out of 12

I’d say there is a strong case towards considering fructose a poison just like alcohol.  The only reason why it is not regulated like alcohol is because it doesn’t produce and short term problems, and because their is a lot of money behind it.

I’m going to stop here and let you think for a while.  If you want and comment please do.  I recommend you watch the whole video, because it is pretty enlightening.

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8 Thoughts on “Fructose is not Glucose, it is a poison

  1. Mike in Arizona on May 25, 2011 at 9:23 pm said:

    Great post! Dr. Lustig is the man!

  2. While I am not a big fan of eating a lot of processed sugars you are saying that we should not eat any fruits cause they have fructose. At least that is my interpretation ob above. Everyone seems to want to blame XYZ for the obesity issue and not focus on the real cause. Eating more and doing less. You can’t take in more calories than your body needs and not expect to gain weight.

    The liver holds about 100 grams of glycogen so not sure how it can hold in infinite amount. Muscle can hold roughly 300-400 grams of it.

    We have tried blaming fat for the weight yet eating less of it has not done much as the weight just keeps going up and up.

    If we would be more active and control calorie intake we would be a lot better off then looking for a scapegoat.

    • Fruits have been manipulated to have more sugar than what they had before, some fruits (i.e oranges) are like candy bars. I personally still eat a lot of fruit especially after my workouts. I have stopped drinking natural fruit juices, and decided to make my own natural iced teas (I place a little bit of fruit in boiling water with some tea bags and spices like cloves or cinnamon). If I’d want six pack abs I’d probably stop eating them or cut my portions down to 4 a week, and start eating lots and lots of vegetables.
      In his presentation Dr. Lustig mentions that the liver can hold a lot of glycogen without going into liver failure as happens to patients with von Gierke’s disease. The normal amount is 100 g as you stated.

    • Gray Grantham on August 17, 2012 at 7:26 am said:

      My initial reaction was: If Fructose is poison and Sugar is 50% Fructose, then Sugar is Poison and likewise all fruits and vegetables that have high amounts of Fructose are Poison.

      So I stopped eating all fruits. Now here is what is wrong with that thinking: When you consume liquid fructose (Pepsi, Coke, etc..) the fructose goes unimpeded to the liver. When you consume fruit, the fructose is contained in a mass of fiber, which prevents its rapid absorption into the digestive system.

      Dr. Lustig Points out in his video “Sugar, The Bitter Truth” you would have to consume 12 Oranges to get the fructose equivalent in 1 can of Soda. However even if you consumed 12 Oranges your liver would not see most of that fructose as most of the fructose in fruits will remain in the fiber of the fruit as it passes through the digestive tract.

      So even though the average large size banana has the equivalent of 5 teaspoons of Sugar, the net effect is a banana will deliver much less fructose to the liver.

      Regarding Fat: Dr. Lustig points out that fat used to be the preferred method of food manufacturers flavoring foods, however when the Food industry moved away from fat as a flavoring agent in food they went to more sugar and in particular High Fructose Corn Syrup, so the net effect of removing fat from our diet is that our entire society has gotten fatter.

      If the food industry were to reverse course and remove the Sugar/HFCS from the food and restore fat as a flavoring agent our entire society would get healthier, not because fat is healthy to eat, but because it is healthier than fructose.

  3. Pam Bennett on July 12, 2011 at 7:35 pm said:

    Thanks for a great summary of the video. I’ve shown it in many of my college biology classes and it is so full of startling information that it’s difficult to absorb with only one exposure. I will certainly refer my students to your website so they can review and reflect on some of the points they may want to go back to. I think the apparent contradiction about how much glycogen the liver can store is addressed by Dr. Lustig’s comment that in glycogen storage diseases the liver enlarges. Although the liver has a huge capacity to regenerate and repair itself, non-alcoholic steatohepatitis and cirrhosis are evidence that it’s not an unlimited capacity.

  4. veggienft on July 18, 2011 at 8:46 am said:

    Exercise can work to mitigate the ill metabolic effects of fructose. Exercise burns through fructose-created adipose fat. But more importantly exercise increases cellular energy expenditure via oxidation instead of fermentation. The Donnan equilibrium says a cell can metabolize no more than 12% of energy through fermentation. 88% must be metabolized through oxidation. Fructose supplies substrates which cannot be oxidized. They must be fermented. Ingested fermentation-only substrates in excess of the Donnan equilibrium cause phosphorus depletion and cell damage.

    Exercise causes cells to burn through non-fructose substrates at highly accelerated rates, making existing fructose substrates represent a smaller portion of potential cell metabolism. Increasing oxidation increases total metabolism, and makes fructose-dictated fermentation a smaller portion of total metabolism. Pre-exercise cells with fructose substrate which would force fermentation higher than the 12% Donnan cap may fall under the Donnan cap after exercise.

    Does exercise help? Yes, but not for the reasons stated by Mr. Cabral. If you can disregard all of the horrendous non-metabolic effects of fructose, exercise can make it so that small amounts of fructose won’t harm you metabolically. However, ongoing vigorous exercise is required without fail, and fructose ingestion must still be held under the level which places fructose substrates under the Donnan equilibrium.

  5. I think you overlooked something he said in the video. You missed an important point here. Lustig makes a point of showing that HCFS and sucrose are identical. They’re equal. Equally bad. The problem with HCFS isn’t that it’s worse than sugar, it’s that it’s CHEAPER than sugar, and that’s why it’s in everything.

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