Context is everything with fructose
Studies indicate the problems with fructose, or any sweetener, occur when consumed in excess. So how much fructose is okay and what’s the limit? The answer is: It depends.
The source of your fructose greatly determines how it is metabolized
When people eat whole foods that contain fructose or glucose, they naturally tend to reduce their calorie intake, simply because the stomach can only hold so much. There is an automated compensation to reduce overall daily calories as well as all the benefits of fiber. Not so, when consuming a beverage sweetened with fructose or glucose. The one or two soft drinks per day easily lead to inadvertent overfeeding.
The condition and activity level of the individual impacts how fructose is metabolized
Kris Gunnars, BSc of
Authority Nutrition sums it well:
“Athletes or highly active individuals can eat quite a bit of fructose without problems, because their livers will turn the fructose into glycogen – a storage form of glucose in the liver. However, when someone’s liver is already full of glycogen (which is true of most people), the fructose will be turned into fat (study).”
Dr. Lustig
wrote this for The Guardian: “The food industry is fond of referring to a 1999 study showing that liver fat generation from oral fructose occurs at a very low rate (less than 5%). And that’s true, if you’re thin, insulin sensitive, fasting (and therefore glycogen-depleted), and given just fructose alone (which is poorly absorbed). Conversely, if you’re obese, insulin resistant, well fed, and getting both fructose and glucose together (like a sizable percentage of the population), then fructose gets converted to fat at a much higher rate, approximating 30%. In other words, the toxicity of fructose depends on context.”
Chris Kresser doesn’t agree that we need to take as strong a stance against fructose. Nevertheless, I still hear him summarizing about the same way. In a blog post Chris states,
“Fructose-sweetened beverages like soft drinks and juice cause metabolic problems when calories are in excess, and studies have shown that people are not likely to compensate for the additional calories they get from such beverages.” Chris doesn’t see a problem with an occasional glass of fruit juice,
“unless you have a pre-existing blood sugar issue.”
Dr. Mercola advises:
“Four out of five Americans have insulin and leptin resistance. This also includes people who are overweight, diabetic, hypertensive, or taking a statin drug. If you fall into this category, it would be prudent for you to restrict your fructose consumption to about 15 to 25 grams of fructose per day from all sources. Those who are normal weight and relatively healthy may also benefit from reducing their intake of fructose, particularly from foods containing high fructose corn syrup or sugar, as the effects of high sugar and HFCS intake may have effects that build up over time.” Of the advised 25 g daily limit, Dr. Mercola says,
“If you are a raw food advocate, have a pristine diet, and exercise very well, then you could be the exception that could exceed this limit and stay healthy.”
Dr. Richard Johnson is the head of nephrology at the University of Colorado and is actively engaged in clinical research. According to Dr. Johnson, if you exercise on a regular basis, a
small amount of fructose can actually be quite beneficial. The fructose will accelerate glucose absorption in your gut and improve muscle performance. That said, it really depends on
how your body metabolizes the fructose. The human body normally cannot absorb fructose well. But the more fructose a person eats, the more the transporters that allow for fructose uptake in the gut are enabled… and the more fructose the body will absorb. As an example, lean children tend to only absorb about half of the fructose they consume, whereas
obese children who have fatty liver disease absorb close to 100 percent.
