http://www.parrilloperformance.com/2009/03/13/the-additive-that%E2%80%99s-making-us-fat/
The Additive That’s Making Us Fat
March 13, 2009 by admin
You may not realize it, but we’re being poisoned by a common additive present in a wide array of processed foods like soft drinks and salad dressings, store-bought cakes and cookies, snacks, breakfast cereals and breads. I say “poisoned” because Fructose this ubiquitous additive is increasing our risk of obesity, diabetes, hypertension, and atherosclerosis.
The additive I’m referring to is high-fructose corn syrup. It is so ubiquitous in refined foods and so over-consumed by the average American (often without realizing it) that many experts believe our country will encounter even more obesity and metabolic disease (like diabetes) in the future.
High-fructose corn syrup, which is made from corn, was developed in the 70s as a low-cost sweetener for foods. While regular table sugar (sucrose) is 50% fructose and 50% glucose, high-fructose corn syrup can contain up to 80% fructose and 20% glucose.
Fructose is fructose is fructose! High fructose corn syrup and fructose are basically the same. As I noted above, high fructose corn syrup is made of mostly fructose. Fructose is a naturally-occurring sweetener found in fruits and honey.
Eating too much fructose of any type is problematic because fructose is metabolized differently from glucose. Fructose is converted to fat in the liver and can be readily stored as body fat. That’s why fruit and processed foods are not recommended in the Parrillo Nutrition Program. Of course, fruit is generally healthy, containing vitamins, minerals and fiber. But the Parrillo Program is based on achieving the best possible results. To that end, vegetables are a source of these nutrients because most vegetables do not contain fructose.
It would be assumed that since fruit is a carbohydrate it would react just like other carbs in the body. However, that is not the case. Nearly all the calories from fruit are in the form of simple sugars, and the most abundant of these is fructose.
Fructose can do three things in the body: First, it can be converted to fat in the liver; it preferentially fills liver glycogen stores so that even good complex carbs are more prone to spill over into fat; and it cannot be used by the muscles to recover glycogen. Muscle does not have the enzymatic machinery needed to convert fructose into glycogen, so fructose represents a dietary carbohydrate load targeted for the liver (1,2).
In the liver, two things can happen with fructose. First, fructose can be absorbed by the liver cells, converted to glucose, and then stored as liver glycogen. Second, the fructose can be converted to fat through an enzyme that operates as a switch to decide if a sugar gets stored as glycogen or converted to fat. Fructose completely bypasses this enzyme and is readily converted to fat by the liver.
So a large portion of the fructose simply gets converted directly to fat and released into the bloodstream. Bam. You get a dose of fat. But the damage doesn’t stop there. The rest of the fructose gets converted into liver glycogen. That sounds okay, until you stop to think about it. You see, once liver glycogen stores are full the liver says, “We’ve got all the glycogen we can hold, so any more carbs coming in here we’ll just convert to fat.” Fructose preferentially repletes liver glycogen instead of muscle glycogen (2) and shifts the liver into fat-storing mode. This is exactly what we don’t want. We need some liver glycogen, to be sure, because this is what keeps blood sugar levels steady. But when liver glycogen stores are full, this is when dietary carbs start to “spill over” into fat stores.
The third problem is that fructose cannot be used to replenish muscle glycogen, so on a high fructose diet liver glycogen stores are filled and we start converting carbs into fat without ever filling muscle glycogen stores. This scenario is a carbohydrate nightmare.
Fructose is the worst carb source for exercisers you can imagine. If you wanted to design a supplement to ruin your physique, it would be a fructose-based energy bar. Unfortunately, the vast majority of the bars out there rely on fructose as their major carb source, because it’s cheap. Parrillo supplements are made the way they are for a reason. We use rice dextrin in our bars and low DE maltodextrin in Pro-Carb™. Both are long chain glucose polymers. Sure, high fructose corn syrup or fruit juice concentrate would be cheaper, but we’ve designed our supplements to be the best, not the cheapest. You might be surprised that a seemingly small difference like using glucose instead of fructose would be important, but it can make the difference between winning and losing if you’re a bodybuilding competitor.
In summary, fructose does three things: a large portion of it is converted directly to fat by the liver, it preferentially fills liver glycogen stores so that even good carbs are more prone to spill over into fat, and it cannot be used by muscle to recover glycogen. Calorie for calorie, the only nutrient that will make you fatter than fructose is fat itself. Besides that, I don’t have a problem with fructose.
Now you know how to control the traffic of carbohydrates through the metabolic pathways of your body and direct carbs to muscle while minimizing their conversion to fat. You also know when somebody starts telling you how wonderful their fructose bar is, you’d better put on your hip waders.
References
1. Shafrir E. Fructose/sucrose metabolism, its physiological and pathological implications. Sugars and Sweeteners, Kretchmer N and Hollenbeck CB, Eds. CRC Press, 1991, pp. 63-98.
2. Paige DM. Clinical Nutrition. C.V. Mosby Company, St. Louis, 1988, pp. 703-704.
