A Foray Into Fructose

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We continue to delve into various sweeteners. This week, we’ll start to take a closer look at fructose and its counterpart, high-fructose corn syrup, with which you’re undoubtedly somewhat familiar.

Fructose: What Is It?
Fructose (sometimes called levulose) is a monosaccharide, or a simple sugar. It’s slightly different than glucose in terms of its molecular makeup. You might know it as “fruit sugar” because it’s found in fruits, some vegetables, and honey. Dates, raisins, and figs are prime sources of fructose, but it’s found in other fruits as well.

Fructose comes in a crystalline form, which is 100% fructose, and is then made into a syrup for use, commercially, in foods and beverages. Fructose makes up one half of sucrose, or table sugar; the other half comes from glucose.

Many people have been told that fructose is a better type of sweetener to use due to the way it’s metabolized. Fructose, when ingested by itself, is poorly absorbed in the gastrointestinal tract (unlike glucose). Also unlike glucose, fructose doesn’t stimulate insulin secretion from the pancreas. In addition, the body lacks the ability to transport fructose into cells to be used as energy.

Interestingly, fructose has a much lower glycemic index value than sucrose: 19 versus 65. Some people who use fructose as a sweetener find that it has less of an effect on their blood glucose levels than other nutritive sweeteners.

The Dark Side of Fruit Sugar
There are a few potential drawbacks of using fructose.

High triglycerides and LDL cholesterol. In the body, fructose is processed by the liver, and once it’s in the liver it can be used to form triglycerides, a type of fat found in the bloodstream as well as in fat cells. In fact, there’s some evidence that too much fructose in the diet may raise blood triglyceride levels (high triglycerides are linked with heart disease and pancreatitis). Fortunately, it seems to be fructose in the form of high-fructose corn syrup, rather than the naturally-occurring form, that has the most detrimental effect.

However, if you have a high triglyceride level (the goal is a level less than 150 mg/dl), do a mental inventory of your typical food intake. If you’ve been overdoing it with fruit, honey, or any food containing high-fructose corn syrup, you might try cutting back a little. Also, a high fructose intake has been shown to decrease the particle size of LDL (or “bad”) cholesterol in overweight children (smaller LDL particles cause more cardiovascular damage), as well as increase LDL cholesterol levels in adults.

Gout. Who would have thought that fructose and gout would be linked? A study of 50,000 male health professionals indicated that those who drank at least two glasses of fruit juice or two cans of regular soda every day had double the risk of gout compared to nondrinkers. And fructose was up there along with meat and being overweight in terms of risk for gout (think Henry VIII!).

Kidney stones. Data from the Nurses’ Health Study as well as the Health Professionals Follow-Up Study indicated that, after examining the 4,900 kidney stone occurrences over a combined 48 years of follow-up, kidney stones were linked with a high intake of fructose. Fructose seems to increase uric acid levels as well as increase urinary excretion of calcium and oxalate, all factors that can increase kidney stone risk. However, what’s not clear is if fructose occurring naturally or fructose in the form of high-fructose corn syrup—or both—is the problem. And it’s also possible that other forms of sugar could be a contributing factor as well.

Irritable bowel syndrome. As if high triglycerides, gout, and kidney stones weren’t enough to contend with, here comes irritable bowel syndrome (IBS). IBS is one of the most common gastrointestinal disorders, affecting 40 to 50 million people in the U.S. While there are multiple proposed causes of IBS, consuming too much fructose in the form of fruit, fruit juices, and other fructose-containing foods seems to trigger pain, bloating, and diarrhea in many people. This is aptly known as fructose intolerance.

Next week: A closer look at high-fructose corn syrup!

For previous entries on this topic, see the following:
“Sugar Is Sugar, By Any Other Name…Or Is It? (Part 1)”
“Sugar Is Sugar, By Any Other Name…Or Is It? (Part 2).”
“Sugar Is Sugar, By Any Other Name…Or Is It? (Part 3)”

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