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Saturday
Jun192010

Fructose Findings

Mention the word fructose and people often think immediately of high-fructose corn syrup (HFCS). While this is one of the most common ways we consume fructose, it’s not the only way. Even though the public has paid increasing attention to the prevalence of HFCS, fructose itself is found in other forms in our diet. It is even found in some of the foods people think are the healthiest. We’ll take a look at the impact this sugar has on metabolism and where you find it in the diet so you can reduce your intake.

A Sweet Society

The average American consumes 150 pounds of sugar per year. When you look at that figure on paper, it might be easy to dismiss. To put it in perspective, the next time you’re at your fitness center, put a 45-pound, 10-pound, and 2 ½ pound plate on each end of a full length bar in the free weight area, and pick it up. That is a LOT of sugar! Sugar in general can lead to a variety of health problems, but one form of sugar, fructose, may present more problems than others.

Fructose is commonly found in fruit, so it is often thought of as a “natural” sugar. It is also found as part of a sucrose (table sugar) molecule, with sucrose being 50% glucose and 50% fructose. Though the name “high-fructose corn syrup” makes one think it contains a high amount of fructose, the most common form of HFCS is 55% fructose, not much different than regular table sugar. The biggest problem with HFCS is not the amount of fructose in it, but how common this sweetener is in the diet. HFCS is created from treating corn syrup with enzymes that change it from pure glucose to HFCS. Because corn is so cheap, HFCS is much cheaper than table sugar. This makes it easy for food manufacturers to use in processed foods.

In 1970, less than 1% of all sweeteners used in the diet came from HFCS. As of the year 2000, it represented 42% of all sweeteners used. It also led to a significant increase in total sugar consumption, which in 2005 averaged 150 pounds of sugar per individual in the U.S., a 19% increase from 1970.1 This is where some of the criticism of HFCS becomes a little misdirected. It’s not that HFCS is significantly worse than table sugar; it’s that it is so common. Reducing both forms of sugar should be part of a healthy lifestyle.

Fructose and Metabolism

Eating sugar is known to quickly raise blood-sugar levels, which then raises insulin. When sugars are consumed in excess, the sugar itself, as well as chronically high levels of insulin can wreak havoc on an individual’s metabolism. Fructose, however, is different. Fructose does not require insulin to be absorbed, which at one point in time made it an appealing alternative for diabetics. However, research has shown that because of the unique way fructose is metabolized, it can lead to a variety of unwanted effects.

Insulin increases another hormone called leptin, which signals the body to stop eating.2 Because fructose does not raise insulin levels, an individual may not get the signal to stop eating as quickly, and therefore consume additional, unneeded calories. This may be part of the reason individuals can drink a 62 ounce (said another way: a half-gallon) of soda and not be satisfied. Less than half of the sugar in the soda comes from insulin-secreting glucose. The rest of the sugar comes from fructose, which has little effect on helping one feel satisfied.

Fructose and Health Complications

Fructose has been shown in studies to increase the amount of visceral fat, or belly fat in individuals. A 2009 study showed that when comparing glucose and fructose, both sugars led to equal weight gain, but glucose increased subcutaneous fat, whereas fructose increased belly fat, which has been shown to be a greater issue for individual’s health.3

Some studies, but not all, have also shown an increase in triglyceride levels with increased fructose consumption. However, there is growing evidence that fructose consumption may increase the concentration of very-low density lipoprotein (VLDL) and oxidized LDL cholesterol. VLDL levels are not often measured in individuals doing a basic lipid profile, but it is becoming more clear that VLDL cholesterol, not total LDL cholesterol, is a major risk factor for heart disease.

Salt intake has been in the news a lot lately, due to its association with high blood pressure. Research shows that fructose-sweetened foods lead to higher blood pressure as well.4 It can be a double-whammy for those eating processed foods high in both.

A more recent study indicates that excess fructose consumption may lead to the development of non-alcoholic fatty liver disease. The results of a study published in the Journal of Hepatology showed that over half of those with NAFLD consumed one to six servings per week of fructose-containing beverages. Many people don’t realize how prevalent NAFLD is. Thirty percent of adults have it.5

Finally, fructose has been associated with insulin resistance. Although fructose does not increase insulin levels when it’s consumed, it does have an impact on normal blood-sugar regulation. The exact cause is not completely understood, but it appears to be associated with the way fructose is metabolized in the liver.6

Finding Fructose

Historically, humans consumed 16-20 grams of fructose per day, mostly from whole fruit. Today, the average person eats 85-100 grams per day.6 To avoid the chance of eating more fructose than you’d want to, you must know where to find it. Fructose can be found in packaged foods with a variety of names. In some cases, it makes up part of the ingredient and in others may make up the majority of the sugar source. Table sugar, brown sugar high-fructose corn syrup and honey are all about 50% fructose.7 Agave nectar and fruit syrups are even more concentrated with fructose. Agave syrup has been promoted as a healthy sweetener and is found in many seemingly healthy and organic foods, but it is processed much like high-fructose corn syrup. Because it is so concentrated with fructose, it’s a good idea to limit its consumption.

Of course, fruit juice is another common source of high amounts of fructose. Regardless of what the bottle may say, fruit juice is not a replacement for whole fruit. A couple of servings of fruit each day are not an issue since they also provide a variety of vitamins, phytonutrients and fiber, but fruit juices are mainly just concentrated sources of sugar. Dried fruit, if it can be eaten in moderation, provides many of the same benefits of whole fruit. However, it can be difficult to eat in appropriate portions because dried fruit do not provide the same kind of bulk in the diet that the water-filled whole fruit form does.

Summary

For the small amount of time you have to enjoy a soft drink, glass of juice or other fructose-laden food or beverage, the price you may pay is pretty serious. Increased belly fat, insulin  and lipid problems, obesity, high blood pressure and fatty liver disease are just some of the issues surrounding the high amount of fructose we consume each day. Be sure to check your food labels.

References:

  1. Wells FW, Busby JC. Dietary assessment of major trends in US food consumption, 1970-2005. Economic Information Bulletin. 2008;33:18
  2. Bray G, Nielsen S, Popkin B. Consumption of high-fructose corn syrup in beverages may play a role in the epidemic of obesity. Amer Jour Clin Nut. 2004;79(4):537-543
  3. Stanhipe K, Schwarz JM, Keim N, et al. Consuming fructose-sweetened, not glucose-sweetened, beverages increases visceral adiposity and lipids and decreases insulin sensitivity in overweight/obese humans. J Clin Invest. 2009;119(5):1322-1334
  4. Fox M, Briand X. Fructose tied to higher blood pressure: study. Reuters. (http://www.reuters.com/article/idUSTRE58M6D820090923?rpc=28)
  5. Ouyang X, Cirillo P, Sautin Y, McCall S, Bruchette J, Diehl A, Johnson R, Abdelmalek M. Fructose consumption as a risk factor for non-alcoholic fatty liver disease. Jour Hepa. 2008;48(6)993-999
  6. Basciano H, Federico L, Adeli K. Fructose, insulin resistance, and metabolic dyslipidemia. Nutrition & Metabolism. 2005;2:5
  7. Kretchmer N, Hollenbeck CB. Sugars and Sweeteners. CRC Press, Inc. 1991

Written by Tom Nikkola - Director of Nutrition & Weight Management

This article is not intended for the treatment or prevention of disease, nor as a substitute for medical treatment, nor as an alternative to medical advice. Use of recommendations in this and other articles is at the choice and risk of the reader.

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