Yes, it is possible to be intolerant to fruit and vegetables. This genetic disease is rare, but it is a nutritionist’s nightmare.
For most people, eating a wide variety of fruits and vegetables is the foundation of a healthy diet.
But for people with hereditary fructose intoleranceeven a few bites of a juicy slice of watermelon or a few sun-dried tomatoes in a salad can cause serious health problems.
This rare condition is not a food allergy or sensitivity, but it can cause serious complications if it is not identified and properly controlled.
What is hereditary fructose intolerance?
Hereditary fructose intolerance is a rare genetic disease that affects the way the body processes the sugar fructose.
Fructose isn’t just present in fruit — it’s also present in honey, some vegetables, sweetened drinks and many processed foods, such as cakes, cookies, sauces and some types of bread. Fructose can also be added during the processing of certain meats (such as cold meats and sausages) and dairy products (such as chocolate milk).
A sucrose (table sugar) and sorbitol (a sugar substitute found in chewing gum, toothpaste and medicines) also contain fructose or are converted to fructose during digestion. This means that people with hereditary fructose intolerance also cannot tolerate these sugars.
These people do not have the enzyme aldolase B, essential for breaking down fructose.
As a result, fructose accumulates in the liver, kidneys and intestines, which can cause serious problems such as seizures, coma and, in extreme cases, liver and kidney failure.
How common is it?
Hereditary fructose intolerance is passed on when both parents carry the responsible gene.
It is considered a rare disease, affecting around 1 in 10,000 people.
It usually becomes evident when babies start eating solid foods, including fruits, vegetables or porridge sweetened with fructose.
In adults, the condition may be misdiagnosed, confusing with diseases such as glycogen storage disease, eating disorders or recurrent hepatitis.
Due to this similarity of symptoms, it can remain unnoticed for years.
How does it differ from an allergy or sensitivity?
Hereditary fructose intolerance is very different from a food allergy.
A food allergy involves the immune system, which reacts to a food (for example, cow’s milk protein) as if it were harmful, e.g.causing symptoms such as hives, swelling of the mouth or difficulty breathing.
It also differs from a food sensitivity, such as lactose intolerance or non-celiac gluten sensitivity, which do not involve the immune system, but can cause discomfort (bloating, intestinal changes, abdominal pain).
Hereditary fructose intolerance is a genetic condition, not related to the immune system.
It is also different from fructose malabsorption (previously informally called “fructose food intolerance”), a milder digestive condition in which the small intestine does not absorb fructose well, causing bloating, gas and abdominal pain.
How do you know if you have the condition?
In babies and young children, symptoms may include vomiting, unusual drowsiness or irritability, refusal to eat, and difficulty gaining weight.
Some children instinctively avoid sweet foods, which can mask the condition until later in childhood or adulthood.
In adults, symptoms may include chronic abdominal pain, fatigue, and unexplained low blood glucose levels. Doctors can observe liver enlargement, changes in liver tests or signs of fatty liver.
The diagnosis is confirmed through genetic testing or a specialized glucose tolerance test. However, for many people, the diagnosis comes after years of confusion and failed dietary attempts.
How is it treated?
There is no cure for hereditary fructose intolerance. But it can be successfully managed by strictly eliminating fructose, sucrose and sorbitol from the diet.
Reading product labels becomes essential in everyday life, as even sauces, medicines and toothpastes can contain these sugars.
People with this condition should pay attention to:
- Fruits: avoid all fruits, juices, canned fruits and fruit products.
- Cereals/grains: avoid cereals with added sugars, honey, molasses, dried fruits or sweet flavorings.
- Pasta, rice and plain grains (like quinoa or buckwheat) are generally safe—avoid flavored or pre-prepared versions.
- Legumes: Most are safe, except the sweetest ones (peas, corn, beets, onions, pumpkin, sweet potatoes, carrots and zucchini).
- Bread: only those made without added sugars or sweeteners.
- Desserts and dairy products: avoid sweetened desserts and flavored yogurts (natural ones are generally safe). Be careful with plant-based drinks (like almond milk), which often have added sugars.
- Proteins: Unsweetened red meat, chicken, fish, eggs, tofu, and tempeh are safe. Avoid processed meats (sausages, ham) or marinades.
- Other foods: be careful with sauces, seasonings and condiments as they may contain hidden sugars or sorbitol. Opt for homemade versions with safe ingredients.
The importance of awareness
If someone avoids certain foods or gets sick after eating fruit, don’t assume they’re weird or that they’re dieting — they may have hereditary fructose intolerance.
One Greater public awareness of this rare condition may enable diagnostics earlier and better support for those affected.
For parents, note a Sudden aversion to sweets, repeated vomiting or slow growth can be an important sign.
And for doctors, considering hereditary fructose intolerance as a possible cause of unexplained digestive problems, hypoglycemia or liver changes can make all the difference.
