Fructose is a sugar found naturally in fruits, honey, and agave, as well as in various processed foods. A fructose-free diet eliminates all forms of fructose entirely, whereas a low-fructose or fructose-restricted diet limits or restricts high-fructose foods. Depending on the individual’s tolerance, a fructose-restricted diet may also restrict foods high in fructans (chains of fructose sugar), sucrose (a sugar that contains equal parts glucose and fructose), and sorbitol (a sugar alcohol that is converted into fructose).
Those with forms of fructose intolerance should follow a fructose-restricted diet including individuals with:
Hereditary fructose intolerance is often discovered shortly after a baby begins to eat baby food or once a baby is fed formula. It may be diagnosed via an enzyme assay, which is a test that requires a liver biopsy to measure the activity of enzymes that break down fructose. A fructose tolerance test can also be used to diagnose hereditary fructose intolerance. This test involves monitoring an individual’s response to intravenous fructose administration. More recently, genetic testing has been utilized for diagnosing hereditary fructose intolerance, which is the least invasive approach.
Fructose malabsorption, on the other hand, may be diagnosed via a hydrogen breath test. For this test, the individual consumes a diet low in fermentable carbohydrates for at least 2 days prior to the test. They will then drink a fructose-containing solution and blow into a device that measures hydrogen gas, every 15-30 minutes for up to 3 hours. If the individual has fructose malabsorption, there will be a rise in breath hydrogen. Another method of diagnosis is working with a physician or dietitian to eliminate high-fructose foods from your diet, to see if symptoms resolve. Higher-fructose foods may then be slowly reintroduced, to determine fructose tolerance threshold.
While tolerance to fructose may vary based on the individual, foods containing less than 3 grams of fructose per serving, less than 0.5 grams of fructose in excess of glucose per 100 gram serving, and less than 0.5 grams of fructans per serving, are considered low in fructose.
Foods high in fructose that may need to be avoided or limited by those with fructose malabsorption include (but are not limited to):
The Fig app makes it easy to avoid these foods. Quickly scan foods at the grocery store to check if they’re likely high in fructose. Easily find low fructose alternatives to your favorites.
It is important to note that those who are sensitive to fructose may also be sensitive to other types of carbohydrates that are highly fermentable by our gut bacteria, such as fructans, polyols, galactooligosaccharides, and lactose. If you still experience symptoms after eliminating high-fructose foods, it may be helpful to eliminate other “high FODMAP” foods under the guide of a registered dietitian, to see if you experience further symptom improvement.
For those following a fructose-restricted diet, it’s important that you read ingredient labels to check for high-fructose ingredients that may be hiding in foods, beverages, and even dietary supplements. The Fig app makes this simpler by helping you identify low-fructose foods and beverages quickly and easily! Additionally, the Monash app can help you determine appropriate portion sizes of fructose-containing foods, to avoid turning a low-fructose food into a high-fructose food by eating too large a portion size in one sitting.
Additionally, for those with fructose malabsorption, it is helpful to keep portions of fruit to about 1 cup or less at a time. This will help you avoid consuming too much fructose at once, as low-fructose fruits can still contain small quantities which accumulate in larger portion sizes. Limiting your intake of added sugars is also helpful, to ensure that you are not consuming too much sucrose, which can provoke symptoms in larger quantities for certain individuals.
When it comes to packaged baked goods, candy, soda, sweetened juices, and condiments, proceed with caution, as these foods often contain high-fructose ingredients such as high-fructose corn syrup.
It can be helpful to know that consuming glucose-containing foods along with foods that contain small amounts of fructose, can help you to better absorb the fructose. Also, when a food contains around the same amount of glucose and fructose, it is better absorbed compared to foods with more fructose than glucose, which is referred to as “free fructose.”
Lastly, while not all sugar alcohols contain fructose, they can further impair your ability to digest fructose and contribute to digestive upset, so many with fructose malabsorption find it helpful to avoid them altogether.
Although fructose is found in many heavily processed foods, it is also naturally found in highly nutritious foods like fruits and vegetables, therefore there are a few nutritional considerations to keep in mind on a fructose-restricted diet.
Fiber is not only important for gastrointestinal health, it also promotes a healthy blood lipid profile, stable blood sugar, and helps us feel full after we eat. Many high-fructose fruits and vegetables are excellent sources of fiber, so if you must avoid these foods, it’s important to be sure that you’re including plenty of alternative fiber sources suitable for you, like low-fructose vegetables, fruits (in portion sizes of 1 cup or less), whole grains, beans, legumes, nuts, and seeds.
Vitamin C is an essential vitamin with antioxidant properties. It is also needed for collagen synthesis, playing a key role in wound healing, and maintaining connective tissues like tendons and ligaments. Many high-fructose fruits and vegetables also happen to be high in vitamin C, so you’ll want to be cognizant of including plenty of low-fructose vegetables and some low-fructose fruits into your diet to meet your needs.
Only those with hereditary fructose intolerance or fructose malabsorption need to follow a fructose-free and fructose-restricted diet, respectively. It is also important to note that those with fructose malabsorption have varying degrees of fructose tolerance, so eliminating all high-fructose foods entirely may not be necessary. To determine your specific threshold for fructose tolerance, it is best to work with a registered dietitian to guide you and minimize unnecessary dietary restrictions.