Are Fructose Fears Unfounded?
Is fructose to really to blame for rising rates of obesity? How much fructose can you safely consume?
The other day, some of us were having a https://www.facebook.com/NutritionDiva/posts/10151534224635538 and a reader posted a list of scary statements about fructose, anxiously demanding to know whether or not they were accurate. His list included things like this:
“You can eat as much fructose as you want but you’ll never feel full. In fact, you’ll feel hungrier;” and,
“Fructose is converted directly into fatty acids in the liver;” and,
“Fructose leads to insulin resistance, Type 2 diabetes, and metabolic syndrome;” and,
“Eating fructose is like eating invisible fat because it slips past the body’s defenses. Therefore we need to avoid eating fruit during weight loss.”
Apparently, these “facts” were gleaned from a book written by a television personality associated with a popular weight loss reality show. According to her Wikipedia entry, this individual has /health-fitness/healthy-eating/reliable-sources-of-nutritional-information in nutrition, biochemistry, or health sciences. Her degree is in Media and Communications—which is perfect…because she has a career in television.
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Unfortunately, she’s also written a number of books on weight loss and acts as a “weight loss coach” on television. I say “unfortunately,” because she appears to be spreading a lot of misinformation, faux science, and needless anxiety. And when it comes to fructose, there’s /health-fitness/healthy-eating/is-high-fructose-corn-syrup-worse-than-sugar.
So, are these charges against fructose true? Some of them—such as the fact that fructose is converted into fatty acids in the liver—have a basis in fact, but are not nearly as ominous as they sound. Others—such as the one about fructose acting as an invisible fat and slipping past the body’s defenses—are closer to paranoid fantasies. Let me see if I can clarify what you do—and don’t—have to fear from fructose.
Let me just take a quick time-out to mention say that there is a fairly rare medical condition known as fructose malabsorption, in which even small amounts of fructose can cause problems. The information that follows would not necessarily apply to these folks.
We Don’t Eat Fructose, We Eat Food
First of all, when considering the impact of fructose on the body, it’s important to remember that we don’t eat fructose. We eat food.
And there are no whole foods that contain only fructose. For that matter, except for the pure fructose sweetener that’s made for diabetics, I can’t really think of any processed foods that contain only fructose. Virtually all foods that contain fructose—including fruit and even high fructose corn syrup—also contain other sugars, such as glucose, maltose, galactose, sucrose, and/or lactose.
Many of the concerns that people have about fructose would only be valid in the context of a 100% fructose diet. For example, while it’s true that fructose does not trigger the release of hormones that signal satiation (or fullness), those hormones are triggered by other nutrients in foods that contain fructose. What’s more, these appetite control hormones are not the only things that influence your sense of satiation. As I talked about in my show on /health-fitness/healthy-eating/3-tips-on-how-to-eat-less-without-feeling-hungry, your stomach also has special receptors that can sense when your stomach is full—sending signals to your brain to stop eating. These sensors respond the same way no matter what type of nutrients are in that food.
My point is that the facts about how a molecule of fructose is metabolized don’t tell us much about the realities of how foods containing fructose affect the body. The foods you eat contain a lot more than just fructose—and digestion involves a lot more than a single metabolic pathway.
The Dose Makes the Poison
The other problem with many of the charges against fructose is that they are missing two important words: “excessive consumption.” Fructose does not cause weight gain, /health-fitness/mens-health/what-is-type-2-diabetes, and metabolic syndrome. Excessive consumption of fructose might. But again, excessive consumption of fructose is invariably accompanied by excessive consumption of other things as well.
A primary source of both fructose and glucose in the modern diet is soft drinks. Our intake of soft drinks has more than doubled in the last 30 years. And I do believe that immoderate soda consumption is an underlying factor in the rising tide of obesity, Type 2 diabetes, and metabolic syndrome. But I don’t see how we can lay the responsibility for that exclusively at fructose’s door.
Remember, we don’t consume fructose by itself. If you’re consuming enough fructose to be risking fatty build-up in your liver, you’re also consuming enough glucose to put you at risk of insulin resistance, and enough excess calories to make you gain weight. In other words, we all know that consuming too much /health-fitness/healthy-eating/is-natural-sugar-better-for-you has a number of harmful effects on the body. Overstimulation of the fructose pathway is just one of the many ways in which excessive sugar consumption wreaks its havoc.
But it does not necessarily follow that fructose is toxic at any dose. And it certainly doesn’t follow that you have to avoid fruit in order to lose weight.
Fructose as Part of a Balanced Diet
If I open up a can of red paint and apply it to my wall, I’m going to get a very dramatic blood red wall. If I pour a little of that red paint into a gallon of white paint and also add a little yellow, I’m going to get a pale orange wall—quite a different effect. Likewise, while eating huge amounts of pure fructose would probably have some very dramatic effects on the body, the amount of fructose you’d get in a reasonably balanced diet is not going to hurt you.
What’s reasonable? For most people, I suggest limit fruit to two four servings a day. At most, only one of those servings should be in the form of /health-fitness/healthy-eating/drinking-juice-healthy. (Ideally, none would.) In addition, limit your intake of added sugars from sweeteners, desserts, sweetened beverages, and other processed foods to less than 10% of your daily calories. Here’s a whole show I did on /health-fitness/healthy-eating/how-to-reduce-your-added-sugar-intake.
If you’re following this basic prescription, you have nothing to fear from fructose.
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About the Author
Monica Reinagel is a board-certified licensed nutritionist, author, and the creator of one of iTunes’ most highly ranked health and fitness podcasts. Her advice is regularly featured on the TODAY show, Dr. Oz, NPR, and in the nation’s leading newspapers, magazines, and websites. Do you have a nutrition question? Call the Nutrition Diva listener line at 443-961-6206. Your question could be featured on the show.
