Medical Articles

The Devil in the Fructose

I recently saw a fantastic lecture titled "Sugar: The Bitter Truth" given by Dr. Robert Lustig professor of Pediatrics at UCSF. I will try to summarize the basic points here, but If you have the time I highly recommend watching it. There is an epidemic of obesity in our country not only in adults but in children as well. Dr. Lustig is seeing an epidemic of obesity in children as young as 6 months and through research that he and is colleagues have done and collected have come to the conclusion that the main culprit is the sugar fructose. In his lecture he breaks down the biochemistry of how fructose is metabolized in our body and comes to the conclusion that fructose is a toxin- as toxic as alcohol.

How did we as a nation come to increase our fructose consumption so dramatically? In 1980 Dr. Ancel Keys wrote The Seven Countries Study, which was the first multivariate linear regression study (a study done to find out how different variables have an effect on an outcome) on coronary heart disease and fat. In summary, he found that countries that ate more fat had more heart disease. There are numerous problems with the study, including the fact that he excluded countries that didn't fit into his hypothesis. But more significantly, he stated: "The fact that the incidence rate of coronary heart disease was significantly correlated with the average percentage of calories from sucrose in the diet is explained by the intercorrelation of sucrose with saturated fat." i.e. doughnuts. Wherever there was fat there was sugar. The problem with this study is that in order to properly do a multivariate linear regression study you have to hold fat constant showing that sucrose doesn't work and you have to hold sucrose constant and show that fat still works, which he did not do. He was looking at the sugar and didn't know it, and thirty years of nutrition has been based off of this study, which turned out to be incorrectly interpreted. 1982 the recommendation came (based off of this study) to reduce our consumption of fat from 40% to 30%. When we as a nation reduced our fat intake, we made up the calories with carbohydrates. A low fat diet by definition is a high carbohydrate diet. What happens to our food supply when you take the fat out? In general food has less flavor, and to make up for this companies had to add sugar to make it palatable. Paleolithic man consumed around 15 grams of fructose a day in the form of whole fruit. Prior to WWII consumption was around 16-24 grams per day. In 1978, when high fructose corn syrup was introduced consumption was up to 37 grams per day and by 1994 it was up to 54.7 grams per day. Adolescents today consume about 73 grams of fructose per day, or around 12% of their total calorie intake. The math is something like this. 1 can of soda is 150 calories. 1 pound of body fat is about 3500 calories. So one can of soda a day is 150x365= 15.6 pounds of additional fat per year.. A large amount of those calories come in the form of juices and sodas.

So how does fructose work in our body and why is it so deadly? Unlike glucose, fructose does not stimulate insulin, nor leptin, the hormone that tells your brain you are full. Fructose get metabolized entirely by our liver, eventually leading to what is known as metabolic syndrome, or pre-type 2 diabetes. If we compare the equivalent calories from glucose and fructose we can see the difference. 2 slices of bread is about 120 calories of glucose. Of that, 96 calories (80%) is used by the cells and the liver takes up 24 calories. Most of that gets stored as glycogen, some gets converted to ATP (our main source of energy) and about calorie of that is turned into VLDL (very low density lipoprotein). VLDL is a cholesterol transporter that has been linked to cardiovascular disease. Compare that to 120 calories of sucrose from an 8 ounce glass of orange juice. Sucrose (table sugar) is comprised of two sugar molecules-1/2 glucose and 1/2 sucrose. So of the 120 calories, 60 of it is glucose in which about 40 calories get used by the body and 12 go to the liver. But all of the 60 calories of fructose get metabolized directly by the liver, for a total of 72 calories of sugar that get taken up by the liver. Once in the liver fructose is metabolized much differently than glucose. One of the byproducts of fructose metabolism is the waste product uric acid, which your body disposes of through the urine. However, excess uric acid is what causes not only gout, but high blood pressure as well. Some of the sugar won't make it out and forms a fat droplet in the liver. Excess fat in the liver leads to a disease known as non alcoholic steatohepatitis (NASH). Much more of the fructose will be to VLDL, and much more will be turned into triglycerides. The effects of excess fructose are hypertension, increased risk of heart attacks, pancreatitis, obesity, fatty liver, fetal insulin resistance and addiction. All of the diseases that are associated with type 2 diabetes and obesity.

Fructose changes the way your brain recognizes energy, all in a negative fashion- your Brain gets the signal that you're starving even though your fat cells are saying that you are full. In summary:

  • fructose consumption has increased in the last 30 years leading to the obesity epidemic.
  • fructose is a carbohydrate that gets metabolized like a fat.
  • 30% of the fructose ends up as fat, so a low fat diet isn't really low fat because the fructose/sucrose doubles as fat
  • hepatic fructose metabolism leads to all the manifestations of metabolic syndrome- hypertension, NASH, inflammation, obesity, leptin resistance promoting continued consumption, dyslipidemea, de novo lipogeneis
  • fructose is a chronic hepatotoxin-"it's alcohol without the buzz"

So what about fruit? Doesn't fruit have fructose? Of course it does, but fruit also has fiber. As Dr. Lusting says: "when god made the poison he packaged it with the antidote." Whenever fructose occurs in nature there is way more fiber. Whole fruit also limits the amount of fructose one can consume. Most people will only eat one orange in a sitting, while a glass of orange juice may contain the juice of 4 or 5 oranges (with the fiber removed). Fiber reduces rate of intestinal carbohydrate absorption, increases the speed of transit of intestinal contents to ileum which induce satiety and inhibits absorption of free fatty acids in the colon, which are metabolized to short chain fatty acids which suppress insulin.

Get rid of all sugared drinks, including juice. There are no healthy sweetened beverages. Why is exercise important? It improves skeletal muscle sensitivity to insulin (brings insulin down), reduces stress, thus your appetite goes down and increases your cells metabolism so the sugar doesn't get turned into fat. It has nothing to do with the burning of calories. You can find out more about health and Applied Kinesiology at Dr. Week's Naturopathic blog.


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