As healthcare professionals, we’ve heard our patients’ concerns regarding sugars. In particular, one type of sugar is often demonized – fructose – especially when it’s partnered with the words, high fructose corn syrup. Fructose has been blamed for obesity, diabetes, insulin resistance and high triglycerides, but it’s important to know the facts about fructose before we dispense advice to our patients. Let’s break it down.
Fructose is a naturally occurring sugar found in fruits, some vegetables (like asparagus, zucchini and peas), honey, sugar cane and sugar beets. And, it’s always found naturally in these sources in conjunction with glucose. Yet, no matter the type of sugar, the calories per gram are the same, at four calories per gram.
Even though these different sources of sugar provide the same amount of calories, they are metabolized differently in the body. Glucose, for example, is digested, absorbed, and transported to the liver, then released into the bloodstream where many tissues take up this glucose from the blood to use as energy. This process requires insulin. Fructose, on the other hand, is predominantly metabolized in the liver, and doesn’t require insulin to be utilized.
Fructose has attained “generally recognized as safe status” from the Food and Drug Administration, as it has been noted with much research that consuming fructose either pure or in the form of sucrose poses no adverse effects.
Pure crystalline fructose and high fructose corn syrup are actually two different ingredients. Crystalline fructose is nearly 100 percent fructose. On the contrary, while the name might suggest otherwise, high fructose corn syrup (HFCS) is broken down into two types: HFCS 55, which contains 55 percent fructose and 45 percent glucose, and HFCS 42, which contains 42 percent fructose and 58 percent glucose. Neither of these is particularly high in fructose when compared to sucrose, or table sugar, that is made up of approximately equal amounts of glucose and fructose.
There are benefits to using fructose as a sweetener including how fructose carries a lower glycemic load, or glycemic index, meaning it doesn’t cause a rapid rise and subsequent large fall in blood glucose levels. Glycemic index (glycemic load per gram carbohydrate) is a measure of how carbohydrates affect blood glucose concentrations. As expected, glucose itself has a high value because it is rapidly absorbed into the blood stream; its GI or glycemic load per gram is 100. In contrast, the glycemic load per gram fructose is only 19, while that of table sugar is 65 – midway between its component parts glucose and fructose. HFCS has a similar GI value to table sugar, though its precise value depends on the fructose content of the HFCS that is used.
Fructose is also 1.2 times sweeter than sucrose, allowing for a reduction in the amount of sugar needed to sweeten a food during the manufacturing process. There’s also a flavor enhancement benefit, as the perception of sweetness from fructose actually peaks and falls earlier than glucose and sucrose. Fructose interacts well with other sweeteners, and contributes to a boost in height of baked goods and viscosity of foods and beverages.
It’s clear that excess body fat is the result of excess calories without the opposing release of energy. That means excess calories from any nutrient can contribute to this calorie imbalance resulting in obesity.
There are many factors that can contribute to insulin resistance, including hypertension, dyslipidemia, and obesity itself. Excess body fat, lack of physical activity, and a genetic predisposition can also add to the risk of insulin resistance. And while experimental animals given large doses of fructose have resulted in insulin resistance, this same type of study done on humans has not translated into the same results. More research needs to be done.
Factors like overweight and obesity, lack of physical activity, and a genetic predisposition all contribute to the risk for diabetes (Type 2). Research has not shown a direct correlation between diabetes and fructose. In contrast, it’s important to note that while fructose has a lower glycemic index, which may be of benefit to prevention of blood sugar surges, the American Diabetes Association does not believe the glycemic index to be sufficiently important enough at this time to warrant any changes in existing advice on carbohydrate exchanges.
The only proven risk of nutritive sweeteners like sucrose or table sugar is the risk of tooth decay. However, research has found that fructose causes the least amount of dental caries when compared to other sweeteners.
While fructose has some benefits, it still should be enjoyed with moderation in mind. The American Heart Association recommends 100 calories or less from sugar each day for women, and 150 calories or less from sugar each day for men. And the current Dietary Guidelines for Americans, released in 2015, recommend no more than 10% of daily total calories should come from sugar.
While it is easy to blame one ingredient over another for the cause of much of the health problems in America, it comes down to balance, both on our plates, and in our perception of sugar, while seeking out credible sources of science before dispensing advice.
An award-winning dietitian, Jen Haugen, RDN, LD, is the author of the new book, “The Mom’s Guide to a Nourishing Garden.” Jen specializes in inspiring moms to create the recipe to a nourishing life through gardening, good food, family, and faith. Her TEDx Talk, “How Moms Can Change the World”, features two simple ideas that can transform a family. Connect with her at www.jenhaugen.com or on Twitter @jenhaugen.