Friday, January 29, 2010
Fourth Principle of Good Nutrition: Limit Fructose Consumption
Fructose is a naturally occurring, six carbon sugar, commonly found in fruit and vegetables. It is sweeter tasting than glucose or any other sugars. Fructose is commonly found bonded to a molecule of glucose, comprising one molecule of the dissacharide sucrose (aka table sugar). Humans have consumed sucrose in small, unprocessed quantities for thousands of years. In the last couple hundred years, sugar cane and sugar beat processing has yielded the common sweetener that we know today. In 1975 the United States was introduced to high-fructose corn syrup (HFCS). This 'natural' sweetener is refined from corn. It differs slightly from regular sugar (sucrose) in that it is composed of a mixture of glucose and fructose molecules not bonded together. As the Corn Refiners Association website (www.sweetsurprise.com) strongly emphasizes, HFCS is no different than sucrose.
Whichever sweetener you ingest, sucrose or HFCS, half of the sugar is in the form of fructose and half is from glucose. The problem lies in the fact that fructose, like alcohol, impairs normal liver metabolism in high concentrations. The effects of heavy alcohol use is fairly well known. Alcoholics usually die of cirrhosis of the liver and liver failure. Heavy fructose ingestion (which can only be metabolized in the liver) causes a whole host of metabolic impairments, and is one of the key driving forces for developing the metabolic syndrome.
Fructose (via sucrose and HFCS) consumption has increased dramatically (>1500%) over the last hundred years. In the last 30 years, we have seen an even greater spike do to a couple factors. The first is due to the availability of HFCS, which costs half as much as sucrose. Secondly, the admonishment of fat in the early 1980's by the American Heart Association and USDA, led to the low-fat food craze. Fat was substituted with sucrose or HFCS.
Makes sense for the dairy industry to support the low-fat movement. Take your product, add water (so now it is cheaper to make) and now sell it as a healthier alternative. Even better, add sweetener to it (fat-free chocolate milk) and sell it to schools!
Why Is Fructose So Bad In Large Concentrations?
Glucose, the break-down product of starches, readily enters the blood stream and is taken up by the heart, brain, muscles, and liver. In the liver and muscle, it is stored as glycogen. Fructose, on the other hand, can not be used in the same manner. It travels from the gut directly to the liver where it is metabolized. There, it is converted to triglycerides, packed into VLDL particles and transfered to fat cells. These triglycerides also accumulate in the liver, contributing to a fatty liver.
The by-products of fructose metabolism have other negative phyiological effects. High levels of uric acid are produced, which raise blood pressure, due to uric acid's inhibition of nitric oxide synthesis. Inflammation and insulin resistance are stimulated by other metabolites of fructose metabolism. Sounds like the metabolic syndrome to me.
The Corn Refiners Association explain in their frequently-asked questions section of their website that obesity is simply caused by eating too many Calories of any food and not moving enough. Ah, conventional wisdom! They conveniently leave out the fact that fructose metabolism impairs Leptin function in the brain. What does that mean? Leptin is the hormonal messenger that tells the brain that you are full. Fructose inhibits this hormone, thus leading to an increase in food intake, contributing to a viscious cycle. So much for a Calorie is a Calorie!
Fructose, similar to alcohol, is extremely dangerous in the body in high concentrations. The 75 pounds of fructose per year that Americans are consuming, is toxic and impairs normal physiology. It spurs a pathological cascade and is much more detrimental to our body composition and health than simply eating a few extra empty Calories.
Fructose, in the form of sucrose and HFCS, is seamingly everywhere. The most concentrated sources continue to be in soda, sports drinks, juices, candy, syrups, dipping sauces, condiments, salad dressings and processed sweet snacks. Cut these out of your diet completely and limit your fructose sources to raw, fiberous, vegetables and berries.
Posted by Dan Hubbard, M.Ed. at 12:22 PM