We've all heard about the dangers of eating too much sugar. Recently further evidence has come to light that demonstrates there is a specific component of sugar responsible for its harmful side effects: fructose.
Fructose Dangers: What is Fructose?
Fructose is a monosaccharide, a simple sugar. It is sweeter than other forms of sugar. Refined cane sugar is essentially half fructose and half glucose. Honey is typically higher in fructose (which is why it's so sweet). And high fructose corn syrup is about 55 percent fructose.
What Makes Fructose So Dangerous?
Fructose and glucose are metabolized in two very different ways. Glucose is absorbed directly and mostly used for energy by cells throughout the body. Fructose, however, is processed in the liver and is generally converted into VLDL (Very Low Density Lipoprotein) cholesterol and triglycerides.
There are genuine concerns that fructose contributes to health problems like increased inflammation, high blood pressure, excess uric acid, high triglycerides and high VLDL cholesterol. Fructose also contributes to fatty liver deposits much in the same way alcohol does.
Another problem with fructose is that it doesn't signal the body's satiety mechanisms. In particular, fructose does not stimulate the release of leptin, an important hormone in appetite control as well as other important metabolic processes. Over time this can also lead to insulin resistance and eventually diabetes.
On the same note, more fructose dangers stem from its particularly strong level of sweetness. A beverage high in fructose (think soda or fruit juice), for instance, stimulates the pleasure centers of the brain so powerfully that it may lead to increased hunger, cravings, and eventually to an increased body weight set point. In this way, fructose in a concentrated, easily absorbed form (like high-fructose beverages) can impact the body's weight beyond what calories alone can explain. (The connection between flavor, calorie-density and the body weight set point is something I am currently researching and will be talking about more in the future.)
Because fructose does not directly stimulate the release of insulin, many people assume it is a safe sweetener. However, since it affects biochemical systems in a way that can eventually induce insulin resistance, it can actually be quite harmful.
Fructose Dangers: Is Fruit Bad?
It's true that fructose gets its name from fruit sugar, but consuming refined sugar products is not the same as consuming whole fruits. Fruits have protective factors that may counter the risks of consuming fructose, such as fiber and antioxidants. Fruits also contain nourishing vitamins and minerals that many of us are lacking. I personally believe fruit is not inherently unhealthy and should never be regarded in the same light as refined sugar.
Fruit juices, however, contain massive amounts of fructose in a form that can be ingested very quickly. Commercial fruit juices should generally be avoided, as they are refined and generally contain nasty stuff like molds and pesticides. Some experts even say any fruit juice is as damaging as commercial soda beverages because of the way it affects the body.
Keep in mind that fructose consumption does not have to be kept at zero. Before the last century, it's thought that fructose consumption was somewhere around 15 grams per day. Some experts like Robert Lustig suggest an intake below 25 grams per day is relatively safe and will not cause the metabolic problems listed above. Today the average fructose consumption is more than 70 grams per day. So in reality it's not the fructose that's harming our health, but the chronic over consumption of it in highly refined forms. Moderation, as always, is key.