Fructose – The sweet nectar of body fat? |

While there is no question that sugar is not in itself bad for you, the only people who eat massive amounts of it and have no issues with their weight are children and teenagers – and they are not very good judges of what is good for them.

Of all the various fructose-containing sugars, glucose and galactose are the ones most commonly used in food and beverages. Fructose is commonly used for its cheaper price tag and its digestion is accomplished by the body much faster than other sugars. However, our body doesn’t seem to know that.

Fructose is the sugar that comes from plants, most commonly sources within fruit. It is often blamed for being the cause of obesity, but there is another way to think about this and it’s more accurate. How about sugar is the cause of body fat?. Read more about fructose vs glucose and let us know what you think.

Because fructose has become such a big subject in the media (and as a consequence, there are a lot of sound bites with little useful information), we decided to clear the air. So, here’s how we feel about this contentious carbohydrate.

“Juice makes you fat!” says the narrator.

“Diabetes is caused by high fructose corn syrup.”

“You shouldn’t eat fruit because it makes you fat!”

These war cries are undoubtedly familiar to you. And whether you like them or not, they all have something to do with fructose, the much-maligned carbohydrate. Because fructose has become such a big subject in the media (and as a consequence, there are a lot of sound bites with little useful information), we decided to clear the air. So, here’s how we feel about this contentious carbohydrate.

Cavemen and juice boxes

Fructose is often associated with fruit in the general public’s mind. While this is true since fructose makes up a part of the carbohydrate in fruit, we get the majority of our daily fructose from non-fruit sources.

Indeed, the bulk of our fructose comes from high fructose corn syrup and sucrose, which can be found in soft drinks, processed meals, candies, and just about everything else that comes in a bag, box, or plastic container. Not only do we receive fructose from high fructose corn syrup or from fructose in general, but we also acquire it through sucrose (table sugar), which is a disaccharide made composed of glucose and fructose.

500 years ago, the sugar industry was non-existent, and so was fructose in our diets. Fructose consumption was limited to a handful of items like honey, dates, raisins, molasses, and figs, which are all considered “dense” sources. Additional intake of fructose was from grapes, apples, persimmons, and berries. Of course, vegetables and protein foods have limited amounts of fructose and don’t contribute substantially to overall intake.

As you may have guessed, our human forefathers had limited early nutritional exposure to fructose…

…and then the sugar business arrived in town.

In action: a sugar refinery

Sugar manufacturers devised low-cost methods of extracting pure sucrose from sugar cane and high-fructose corn syrup from maize in large quantities. For mainly economic reasons, high fructose corn syrup has become a favored source of sweetness and texture in the food production sector.

Because of this, the price of cane sugar in the United States is artificially high when compared to the worldwide price of maize. (This is due to government corn subsidies and livestock corn overproduction.) Because maize is less expensive than cane sugar, high fructose corn syrup is less expensive to manufacture than sugar. In 1984, major soft drink makers realized the economic benefits of switching to HFCS as their main sweetener. Since then, they haven’t looked back.

Purchasing fructose by the pound

As HFCS intake has increased, so has the obesity pandemic. As a result, many people think there is a link between the two. According to food intake studies, the typical individual eats approximately 79 grams of added sugar per day (316 calories or 15% of caloric intake), with fructose accounting for half of those 79 grams.

It’s disputed if excessive fructose intake promotes obesity or is just another sign of poor diet and inactivity in general (which, in turn, contributes to obesity). Indeed, food lobbyists have used this argument, successfully shielding the HFCS business from government restrictions that might cost billions of dollars. What is certain, though, is that the increase in HFCS intake isn’t helping the problem, and that, in our view, is the most significant argument.

What is the difference between fructose and glucose?

Since we’re on the subject of sugars, let’s take a look at the distinctions between fructose and glucose (the sugar that most of our consumed dietary carbs turn into once they reach the bloodstream).

• Fructose and glucose are absorbed via the gut in distinct ways.
• Furthermore, fructose is absorbed at a slower pace.
• Unlike glucose, fructose does not cause a significant amount of insulin to be released.
• Fructose enters cells via a different transporter than glucose.
• Fructose may supply glycerol, the backbone of triglycerides (fat), and promote fat synthesis once it reaches the liver.
• When administered at a high dosage of about 50 grams, some individuals may be unable to fully absorb fructose. (That’s a lot of fructose.) We’re talking about around 4-5 medium apples here. A 16 oz juice containing HFCS, on the other hand, may contain approximately 45 grams of fructose. (Bye, bye, bye, bye, bye, bye
• The absorption of fructose is accelerated when glucose and fructose are consumed at the same time. One of the reasons why many sports drinks include a combination of sugars is because of this.

As you can see, fructose and glucose have distinct absorption, digesting, and metabolic characteristics. Let’s take a closer look at this.

Fructose metabolism takes place mostly in the liver. Fructose may be converted to glucose derivatives and stored as liver glycogen in the liver, which is beneficial if you’re active.

However, the liver’s ability to do this is limited – which isn’t so good. Indeed, with very high single-serving doses of fructose, the fructose that arrives at the liver can easily be converted to fat. And this is very much more prominent in clients with high blood lipids, insulin resistance, or Type 2 diabetes.

Fructose levels in the blood are no longer directly regulated by hormones. This is one of the reasons fructose has a mild glycemic response, which is generally seen as a benefit.

However, although excessive fructose consumption may contribute to fat synthesis, it does not promote the creation of leptin.

Because leptin is a hormone involved in the long-term control of energy balance, a reduction in leptin production caused by chronic high fructose consumption may have negative consequences for energy intake and body fat regulation.

In other words, with HFCS, the brain never sends out those “I’m full” signals. So you continue to eat.

Although fructose has a low glycemic index and may aid in the replenishment of liver glycogen in the physically active, excessive fructose consumption can result in the formation of new fats in the liver as well as a short circuiting of our energy balance and body fat regulating mechanisms.

As a consequence, eating a lot of high fructose sweeteners has been related to central obesity, low good cholesterol, high bad cholesterol, high triglycerides, and poor appetite control.

Malabsorption of fructose

Fructose malabsorption is another issue linked with fructose intake. It’s categorized as a digestive disease, much like lactose intolerance, gluten sensitivity, and other food-related GI issues. When fructose transporters in the intestinal cells are missing, fructose malabsorption develops. As a consequence, excessive fructose remains in the gut, causing bloating, gas, and diarrhea.

How serious is this issue? Fructose malabsorption affects approximately 30-40% of people in North America and Europe, with only half displaying consistent symptoms.

What is the best way to deal with fructose?

Even after reading this succinct fructose assessment, many individuals are likely to have reservations about fructose. And it’s not without cause.

However, don’t make the mistake of assuming that the tiny quantities of fructose in fruit would cause problems. Remember that all of the issues occur at extremely high fructose consumption, when liver glycogen is likely to be depleted.

Isn’t it true that eating entire, unprocessed, fresh fruits would lead to energy imbalances and body fat gain? Regular intake of fructose-rich fruit drinks and meals, on the other hand, is highly likely to create these issues.

So, when is the best time to consume your fruits? If you don’t have any absorption problems, the best times to eat fruit are first thing in the morning, before workouts, and/or after workouts.

In the end, leading experts came to the following conclusion: natural fructose consumption from an unprocessed, whole food diet is modest and unlikely to have any harmful metabolic effects.

Whole fruits are seldom (if ever) the source of significant body fat issues, as we like to remind people. We don’t know many individuals who go on “blueberry binges” or “pear benders.”

This story was first published on www.t-nation.com.

 

References

To see the information sources mentioned in this article, go here.

Fructose, weight gain, and the insulin resistance syndrome. Elliott SS, et al. 76:911-922 in Am J Clin Nutr, 2002.

Bray, Georgia How dangerous is fructose? 2007;86:895-896 in American Journal of Clinical Nutrition.

Groff JL & Gropper SS. Advanced nutrition and human metabolism. 3rd ed. Wadsworth Thomson Learning. 2000.

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Frequently Asked Questions

Does fructose increase fat?

Yes, fructose is a type of sugar that can increase fat.

Is fructose less fattening than sugar?

Fructose is a type of sugar that is found in fruits and vegetables. It is less fattening than other types of sugars because it does not contain any fat molecules.

How does fructose affect the body?

Fructose is a sugar that is found in many fruits and vegetables. It can be metabolized by the body, but it has been shown to have negative effects on health.

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