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. His research (and that of his colleagues) has led to the conclusion that the main culprit leading to obesity is the sugar fructose. In his lecture he breaks down the biochemistry of how fructose is metab olized in our body and comes to the conclusion that fructose is highly toxic —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 studythat examines how different variables have an effect on an outcome) on coronary heart disease and fat. In summary,Dr. Keys concluded that countries that ate more fat had more heart disease. However, there are numerous problems with the misleading 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.” e.g., doughnuts. He recommended that everyone reduce their intake of fat.

He didn’t take into consideration that wherever there was fat, there was sugar. The problem with his study is that in order to conduct a multivariate linear regression study properly, 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. Unfortunately, 30 years of nutrition information has been based on this study, which turned out to be incorrectly interpreted. In 1982 the recommendation was made (based on this study) to reduce our consumption of fat from 40 percent to 30 percent. When we as a nation reduced our fat intake, we increased our intake of carbohydrates—often in the form of added sugar. 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 lack, companies had to add sugar to low-fat products to make them palatable. Thus people were inadvertently consuming more and more sugar. In contrast to modern man, a Paleolithic man consumed only about 15 grams of fructose a day in the form of whole fruit. Up to the time of World War II, sugar consumption was around 16 to 24 grams per day. This gradually increased. 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. Corn syrup is commonly found in an increasing number of common processed foods.

Adolescents today consume about 73 grams of fructose per day, or around 12 percent of their total daily calorie intake. The math is something like this: one can of soda is 150 calories. One pound of body fat is about 3500 calories. So one can of soda a day (150 calories x365 days) produces 15.6 pounds of additional fat per year. A large amount of calories commonly consumed come in the form of juices and sodas, which are full of sugar—often in the form of fructose. Fructose–often called the fruit sugar– is a type of naturally occurring sugar found inmany fruits (berries, melons, apples), vegetables (beets, sweet potatoes, onions) and honey. Fructose is nearly twice as sweet as sucrose (table sugar) and is commonly used in processed foods partly because it is less expensive to produce than sucrose and it takes less of it to produce the same level of sweetness.

So how does fructose work in our body and why is it so deadly?, Glucose is the main type of sugar in the blood and is the major source of energy for the body’s cells. 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. Doctors are finding an alarming increase in diabetes in children.

If we compare the equivalent calories from glucose and fructose we can see the difference between the two in the way it is processed in the body.. Two slices of bread contains about 120 calories of glucose. Of that, 96 calories (80 percent ) 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 ½ 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 composed of two sugar molecules—1/2 glucose and 1/2 fructose. So of the 120 calories, 60 are glucose in which about 40 calories get used by the body and 12 go to the liver. But all 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 metabolized to VLDL, and much more will be turned into triglycerides. The negative effects of excess fructose include hypertension, increased risk of heart attacks, pancreatitis, obesity, fatty liver, fetal insulin resistance, and addiction as well as all 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 and is a major contributor to the obesity epidemic.

Fructose is a carbohydrate that gets metabolized like a fat.

Thirty percent 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 also 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 four or five oranges (with the fiber removed). Fiber reduces the rate of intestinal carbohydrate absorption and increases the speed of transit of intestinal contents to the ileum, which induce satiety and inhibits the absorption of free fatty acids in the colon. Fructose used in processed foods has no fiber.

To reduce one’s own intake of dangerous fructose, and to maintain a healthy weight, get rid of all sugared drinks, including juice. There are no healthy sweetened beverages. Read labels and buy products that do not contain corn syrup. Further protection from the dangers of ingesting too much fructose is found in regular exercise. Why is exercise important? It has little to do with the burning of calories, but rather it improves skeletal muscle sensitivity to insulin (brings insulin down) and reduces stress, thus your appetite decreases. In addition, exercise increases your cells’ metabolism so the sugar doesn’t get turned into fat.

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