The condition fructose intolerance can affect athletes and negatively influence performance.
If you are unfamiliar with its effects on the body, this post explains what you need to know, as our previous posts did for SIBO and iron-deficiency anaemia.
What Is Fructose Intolerance?
The condition fructose intolerance means the body cannot properly break down and absorb fructose consumed through food.
It can be confused with a fructose allergy, but there is a distinction. Allergy involves the immune system producing an adverse immune reaction to fructose. By contrast, fructose intolerance involves difficulty breaking down and absorbing this sugar.
What Degrees of Fructose Intolerance Are There?
Degrees of fructose intolerance are classified by the individual’s tolerance to this sugar:
- Mild fructose intolerance. Intestinal absorption is reduced, but small amounts may still be tolerated without severe symptoms.
- Moderate fructose intolerance. Absorption is lower than in mild cases, increasing intestinal accumulation. Moderate quantities cause clear symptoms.
- Severe fructose intolerance. Absorption is substantially limited, increasing intestinal accumulation and symptoms. Even minimal intake may trigger clear symptoms.
Regardless of this classification, individual tolerance makes the difference. People do not necessarily experience identical symptoms after the same amount.
What Are the Symptoms of Fructose Intolerance?
Possible fructose intolerance symptoms include:
- Gastrointestinal symptoms: bloating, diarrhoea, gas and abdominal pain
- Nausea and/or vomiting
- Fatigue
- Headache
- Skin changes, such as rashes, itching or hives
These are common symptoms of fructose intolerance, but not everyone experiences all of them or the same severity.
How Is Fructose Intolerance Treated?
Consult a healthcare professional for appropriate diagnostic testing before treatment. Treatment generally reduces or avoids fructose, with greater restriction for more severe intolerance.
It usually starts with an “elimination phase” removing almost all dietary fructose, leaving at most 5 g daily for around 2 weeks. If symptoms improve, a “reintroduction phase” follows, gradually introducing small amounts of higher-fructose foods individually to assess tolerance. Patients generally reach a tolerance of 10-15 g of fructose daily.
What Can and Cannot I Eat with Fructose Intolerance?
Treatment involves reducing or eliminating fructose-rich foods.
Generally, foods highest in fructose needing particular attention include high-fructose corn syrup, honey, dates and raisins.
Other foods to watch include:
- Fruit: mangoes, grapes, apples, pears, plums, cherries, kiwi fruit, peaches, watermelon, figs, pineapple, peppers, tomatoes, papaya, garlic, asparagus, sweetcorn, onions, beetroot, artichokes, mushrooms, red peppers, tomato products such as canned tomatoes and ketchup, milk and fruit in syrup because of fructose syrup content.
- Marinated or processed meats.
- Flavoured dairy products.
- Cereals with wheat as the main ingredient or added nuts.
Also watch processed foods with added fructose, such as soft drinks, juices and sweetened yoghurts, natural sweeteners such as agave syrup and polyols such as sorbitol.
Better-tolerated foods include:
- Fruit: berries such as blueberries, strawberries and raspberries, avocados, bananas, mandarins, oranges and lemons.
- Vegetables: spinach, courgettes, cucumbers, lettuce and carrots.
- Meat and fish.
- Eggs.
- Low-lactose dairy products.
- Cereals: buckwheat flour, maize flour, quinoa, semolina, oats and other cereals without added fructose.
As mentioned, individual tolerance matters greatly: a food tolerated by one person may trouble another. Personalised nutrition planning is essential.
Probiotics for Fructose Intolerance: The Solution?
In people with fructose intolerance , unabsorbed fructose accumulates and is rapidly fermented by colonic microbiota, producing gas, lactate and short-chain fatty acids. The gastrointestinal symptoms described above follow.
There is much speculation about probiotics as a solution, but insufficient evidence confirms this claim.
Some studies suggest certain probiotic strains may help, but further research is required.
What If an Athlete Has Fructose Intolerance?
First, work with a healthcare professional to plan a diet appropriate to the degree of intolerance.
Ensure the athlete obtains enough energy , prioritising low-fructose foods or avoiding fructose where necessary. This is especially important when choosing supplements, because most carbohydrate gels and isotonic drinks contain fructose. Alternative carbohydrate sources are therefore needed.
Everyone differs, so individual treatment is essential. At INDYA | Sports Nutritionists , we prioritise daily contact and high-quality feedback to understand each person’s condition and provide tools to address it.
