Fructose Definition, Sources, and Health Effects

close-up of spoon in a small bowl of sugary syrup
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Sugar has long been a household staple sprinkled over cereal, stirred into coffee, or borrowed from a neighbor in a baking emergency. You used to have just two types of sugar to choose from—white or brown. Since sugar was either kept in a bowl on the table with a spoon or measured out carefully for baking, it was also easy to control how much sugar was in your diet.

Today sugar can take several different forms and many foods contain added or hidden sugars. This is especially true of packaged and processed foods. As a result, people often don't realize how much sugar they regularly consume.

One of the most common forms of sugar is fructose. Understanding what fructose is, how it’s used, where it’s found, and what health effects it can have will empower you to make educated choices about including it in your diet.

Fructose Definition

The white sugar (granulated sugar) in your pantry is known as sucrose, which is made of two simple sugar molecules: glucose and fructose. Therefore, any foods that contain sugar will have fructose in them.

Both sucrose and fructose are refined from natural sources. Sucrose comes from plants, like sugar cane, and small amounts of fructose are found in berries, melons, and apples. It's also found in certain vegetables, including beets, sweet potatoes, and onions.

Since fructose is found in healthy foods like fruit and veggies—which also contain many essential vitamins and minerals—it may not seem like you need to avoid it. However, the reality is a bit more complicated. As a stand-alone sweetener, fructose is nearly twice as sweet as table sugar and causes a similar rise in blood sugar as sucrose.

Fructose Sources

While intake of fresh produce is an important component of a balanced diet, when consumed in excess, the body cannot process fructose effectively.

Seventy-four percent of the foods we eat have added sugar—and not just those with a sweet taste. Added sugars can be found in everything from bottled salad dressing to ketchup.

During the early 1900s, the diet of the average American looked (and tasted) very different from what we’re accustomed to today. According to data collected by the U.S. Department of Health and Human Services (DHHS), some 200 years ago the average American consumed about two pounds of sugar in an entire year.

Twenty years ago, sugar consumption by the average American peaked—in large part due to the growing presence of added sugars. In 1999, Americans were eating about 26.7 teaspoons of sugar a day (this figure doesn’t take into account non-caloric sugar substitutes like aspartame).

In 2019, a person living in the U.S. consumes an average of 152 pounds of sugar each year. That translates to about 2 pounds a week—we eat almost as much sugar in one week as our great-grandparents did in an entire year. 

One of the main ways people ingest added sugars in America today is through sugar-sweetened beverages like soda and energy drinks.

Combined with the presence of added sugars in beverages, another factor contributing to increased consumption is larger portion sizes—especially in drinks purchased at fast food establishments or in bottles.

Prior to the 1950s, the size of bottled soft drinks was much smaller; about 6.5 ounces. Today, the average size of bottled soda as well as servings from soda fountains at fast food restaurants are much larger: Anywhere from 20 ounces to 1 liter is standard.

As a result of these changes, as well as increased marketing of sugary beverages (particularly to children), Americans today drink nearly five times more soda than they did in 1950.

Health Effects of Fructose

In recent decades, we’ve learned more about the potential health effects of increased sugar consumption.

Sugar-sweetened beverages have been associated with an increased risk of obesity, heart disease, and type 2 diabetes in both children and adults.

Added sugar has also been linked to cognitive decline. While sugar is often implicated in cancer risk, the link between sugar and cancer is more indirect. The health effects of consuming excess sugar, particularly weight gain and insulin resistance, may increase a person's risk for certain types of cancer.

To better understand why this happens, remember that most carbohydrates are made up of chains of glucose. When glucose enters the bloodstream, the body releases insulin to help regulate it.

Fructose needs to be processed by the liver. In small amounts, the liver can handle the job effectively. But when too much fructose reaches the liver all at once, it can’t metabolize the sugar fast enough to keep up.

Having excess levels of fructose in the bloodstream can lead to a number of health problems, including the buildup of a substance called uric acid. Too much uric acid can cause gout and kidney stones.

When the colony of bacteria living in your intestines freely feeds on sugar, it can lead to a bacterial overgrowth that upsets the balance of healthy gut flora. Such an imbalance can cause gastrointestinal symptoms like bloating. In some cases, bacterial overgrowth in the small intestine can result in the malabsorption of important nutrients.

Once energy needs are met, the body doesn't have another immediate use for extra sugar. When it's present, the body's organs and tissues will try to compensate. This can result in elevated levels of lipids and glucose in the blood, which can increase a person's risk for metabolic diseases.

One of the ways the liver tries to ease the strain and avoid cellular damage is by converting excess fructose into fat. Over time, continued demand placed on the body by excess sugar can overwhelm the liver, causing it to function less efficiently.

The saturated fats produced by the liver enter the bloodstream in the form of triglycerides, which are generally not good for us. In fact, elevated levels of triglycerides are a risk factor for heart disease.

Excess fructose consumption can also raise levels of LDL cholesterol and may facilitate insulin resistance—which can eventually lead to type 2 diabetes.

In a 2013 study published in the Journal of the American Medical Association, researchers at Yale discovered that when participants consumed fructose instead of glucose, fewer of the hormones associated with feeling full were released.

These findings implied fructose affects the body’s appetite-regulating system. If the hormones responsible for sending “I’m full!” signals aren't triggered when they should be, feelings of hunger persist. This may be one reason excess fructose consumption can contribute to weight gain.

High Fructose Corn Syrup

Fructose is commonly used in processed foods because it's less expensive to produce than sucrose and less is needed to achieve the same level of sweetness. It often takes the form of high fructose corn syrup (HFCS)—fructose combined with corn syrup that has been chemically treated to increase its concentration and sweetness.

The body uses fructose as a source of energy. Since it has a low glycemic index (meaning it does not cause high spikes in blood sugar), it was once believed fructose was a better choice than regular table sugar.

In recent years, the American Diabetes Association has changed its stance on fructose: It's now believed the addition of HFCS to the American food supply has contributed to the rise of obesity and type 2 diabetes.

Manufacturers claim HFCS is about 55 percent fructose and 45 percent glucose. When tested, however, the exact composition seems to vary widely: One study revealed an average of 59 percent fructose in HFCS. Several major brands of soda have been found to contain 65 percent fructose.

More natural sources of sugar have various ratios, too: Honey has about the same fructose/glucose ratio as high fructose corn syrup and Agave syrup can be up to 90 percent fructose. Fruit juice concentrates, which are often used as sweeteners, can have high amounts of fructose and tend to be highly processed—an alteration that strips away the fruit's nutritional value. 

Whether it comes from corn syrup, fruit, or honey, your body handles fructose in the same way. The amount you consume makes the difference and can impact your health.

Average Fructose Content (in grams)
One cup chopped tomatoes 2.5 grams
One can of regular (non-diet) soda 23 grams
"Super size" fountain soda* 62 grams
*using the 55% fructose standard.

How to Reduce Sugar Intake

The DHHS recommends Americans limit their daily sugar intake to 10 percent of the total number of calories they consume. Based on a 2,000 calorie diet, that adds up to around 13 teaspoons.

In reality, the average American consumes around 42.5 teaspoons of sugar each day. With many of those sugars hidden, it’s easy to underestimate how much you’re eating. In fact, unless you regularly check nutrition labels, you may not even be aware that many of the foods you eat even have added sugar.

Due to corn subsidies in the United States, high fructose corn syrup (which is derived from corn starch) is cheap to produce in large quantities, which accounts somewhat for its abundance in the modern American diet. Some of the most common sources include:

  • ​Sugar-sweetened beverages (the largest dietary source)
  • Cereals and cereal bars
  • Baked goods
  • Sweetened yogurt
  • Salad dressings
  • Frozen foods and dinners
  • Condiments

Once you become more aware of the sugar content of the food and drink you consume each day, there are some steps you can take to reduce your sugar intake.

  • Swap out soda for water, flavored seltzer, or plain seltzer mixed with 100 percent fruit juice.
  • Reach for fresh fruits and veggies when you need a quick snack or midday pick-me-up. 
  • Sweeten unsugared cereals with fresh fruit.
  • Be aware that foods labeled "fat-free" are often loaded with extra sugar to make up for the loss of flavor that occurs when fat is removed from the recipe.

Reducing your sugar consumption is a process—you don’t have to cut it out all at once. If you take it slow and make mindful swaps along the way, you'll likely begin to develop a preference for foods that aren’t as overly sweet.

Since added and hidden sugars also often add calories, reducing your sugar intake may also help you manage your weight and is likely to improve your overall health.

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