Many individuals experience digestive discomfort, such as gas, bloating, and abdominal pain, without a clear understanding of the cause. If gluten-free diets haven't provided relief, a fructan intolerance might be the culprit. Fructans, a type of carbohydrate, can be difficult for some people to digest. This article explores fructans, their presence in various foods, and how to manage a potential intolerance through a low-fructan diet.
Understanding Fructans and FODMAPs
Fructans are oligosaccharides, a type of short-chain carbohydrate or sugar, belonging to a larger group known as FODMAPs (Fermentable Oligosaccharides, Disaccharides, Monosaccharides, and Polyols). FODMAPs are naturally occurring sugars found in a wide spectrum of foods that aren't easily digested by our bodies. Some people react more negatively to them, experiencing uncomfortable symptoms.
Symptoms of Fructan Intolerance
Individuals with a fructan intolerance may experience a range of gastrointestinal symptoms, including:
- Gas
- Bloating
- Abdominal pain
- Diarrhea
These symptoms often mimic those of gluten intolerance, making diagnosis challenging, especially since some foods contain both gluten and fructans.
High-Fructan Foods
Fructans are present in many foods, which can be categorized into those containing gluten and those that do not. Wheat and onions are major sources of fructans in the typical American diet.
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High-Fructan Foods Containing Gluten
- Wheat
- Barley
- Rye
- Spelt
- Bread products (bread, pastries, pizza dough)
High-Fructan Foods Without Gluten
- Fruits: Bananas, dates, grapefruit, nectarines, persimmons, plums, pomegranate, watermelon, yacon, apples, pears, mangoes, cherries, figs, nashi pears
- Legumes: Black beans, chickpeas, kidney beans, lima beans, mung beans, navy beans, split peas, red kidney beans, falafels, baked beans
- Vegetables: Artichoke, asparagus, beets, Brussels sprouts, chicory root, fennel, garlic, leeks, onions, savoy cabbage, shallots, snow peas, spring onion
- Nuts: Almonds, cashews, pistachios
- Grains and cereals: Wholemeal bread, rye bread, muesli containing wheat, wheat pasta and rye crispbread
Many of these foods are generally considered healthy, so individuals may need to determine their personal tolerance levels.
Should You Avoid Fructans?
If you don't have a fructan intolerance, there's no need to avoid fructan-containing foods, as they can be part of a healthy, balanced diet and can be considered prebiotic, meaning they feed the good bacteria in the gut. However, if you frequently experience gas, bloating, or other stomach issues without a clear cause, it's worth investigating a potential fructan intolerance. Keeping a food log to track what you eat and how your body reacts can help identify trigger foods.
Diagnosing and Managing Fructan Intolerance
The most definitive way to diagnose a fructan intolerance is through a low-FODMAP diet, a specific elimination diet. This involves systematically eliminating foods containing various FODMAPs, including fructans, and then reintroducing them one by one to identify sensitivities and tolerance levels. It's crucial to work with a registered dietitian during this process to ensure adequate nutrient intake and proper guidance.
The Low-FODMAP Diet: A Three-Phase Approach
The low-FODMAP diet consists of three phases:
- Elimination Phase: Avoid all high-FODMAP foods for two to four weeks.
- Reintroduction Phase: Systematically reintroduce foods to identify triggers.
- Maintenance Phase: Customize your diet based on identified tolerances.
Seeking Professional Guidance
Working with a dietitian is highly recommended when undertaking a low-FODMAP diet. They can provide personalized guidance, help identify suitable food replacements, and ensure adequate nutrient intake during the elimination phase.
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FODMAPs in Foods: A Detailed Look
FODMAPs are found in a wide variety of foods, including fruits, vegetables, grains, cereals, nuts, legumes, lentils, dairy foods, and manufactured foods. This makes following the FODMAP diet a little tricky, as you cannot simply guess which foods will be high or low in FODMAPs. Having a basic understanding about which foods contain FODMAPs makes following the 3 step FODMAP diet for your IBS treatment a little easier long term and helps you to avoid unwanted symptoms of IBS.
Fruits
The main FODMAPs present in fruit are sorbitol and excess fructose. Fruits particularly high in excess fructose include apples, pears, mangoes, cherries, figs, nashi pears, pears, watermelon and dried fruit. Fruits particularly rich in sorbitol include apples, cherries, nashi pears, peaches and plums. Many fruits contain both fructose and sorbitol, for example, apples and pears.
Vegetables
The main FODMAPs present in vegetables are fructans and mannitol. Vegetables particularly rich in fructans include artichoke, garlic, leek, onion and spring onion. Vegetables particularly rich in mannitol include mushrooms and celery.
Grains and Cereals
The main FODMAPs present in grain and cereal foods are fructans and to a lesser extent, GOS. Grain and cereal foods particularly rich in fructans include wholemeal bread, rye bread, muesli containing wheat, wheat pasta and rye crispbread.
Legumes and Pulses
The main FODMAP present in legumes and pulses is GOS. Legumes and pulses particularly high in GOS include red kidney beans, split peas, falafels and baked beans.
Read also: Weight Loss with Low-FODMAP
Dairy Foods and Alternatives
The main FODMAP present in dairy foods is lactose. Dairy foods that are high in lactose include soft cheeses, milk and yoghurt. There are also many dairy foods that are naturally low in lactose, for example butter and cheese. For this reason, dairy foods are definitely not excluded from a low FODMAP diet. Many plant-based milk alternatives are also low in FODMAPs, e.g. soy milk (made from soy protein), almond milk and rice milk. However, milk alternatives do not naturally contain calcium, so remind patients to choose calcium fortified varieties (containing >120mg calcium per 100ml).
Meat, Poultry and Fish
Protein foods such as meats, poultry and fish are naturally free of FODMAPs. However, processed and marinated meats may contain FODMAPs due to the addition of high FODMAP ingredients such as garlic and onion. Low FODMAP choices include plain cooked meats, poultry, seafood, eggs, while high FODMAP options include marinated meats, processed meats (e.g. sausage / salami) and meats served with gravy/sauces that may include high FODMAP ingredients.
Nuts and Seeds
Most seeds are low FODMAP. The main FODMAPs present in nuts are GOS and fructans. High FODMAP nuts include cashews and pistachios, while low FODMAP nuts include macadamias and peanuts.
Sugars and Sweeteners
The main FODMAPs present in sugar sweetened foods and beverages are fructose and sugar polyols (e.g. sorbitol, xylitol, erythrytol). It is a good idea to read the food labels to identify high FODMAP sugars, especially on artificially sweetened drinks and confectionery. High FODMAP sugars include honey, high fructose corn syrup and sugar-free confectionery. Low FODMAP options include dark chocolate, table sugar, maple syrup and rice malt syrup.
Condiments and Sauces
Some dips, condiments, sauces and marinades contain garlic and onion. Ask for them separately or on the side if you are unsure of their FODMAP content. High FODMAP options include garlic / onion based marinades and sauces, vegetarian mince. Low FODMAP options include barbeque sauce, mayonnaise, soy sauce, chutney, cranberry juice.
Fructans as Functional Ingredients
Fructans, particularly inulin, are increasingly used in the food manufacturing industry to increase the fiber content of processed foods. These fermentable fibers act as prebiotics, promoting the growth of beneficial gut bacteria. While this is generally beneficial, it can be problematic for individuals with fructan intolerance.
Fructan Levels in Foods: Considerations
Fructan levels can vary significantly between different foods. Cooking, manufacturing, refining processes, and fermentation can also alter FODMAP ratings and fructan levels. For instance, spelt sourdough bread is lower in FODMAPs due to the yeasts consuming fructans during fermentation. Drying fruit concentrates sugars and can increase fructan levels.
Reintroducing Fructans
After the elimination phase, fructans can be reintroduced to determine tolerance levels. Given the variability in fructan levels across different food groups, it's essential to test one to two foods from each group.
Dietary Intolerances and FODMAPs: The Bigger Picture
Dietary intolerances to fructose, fructans, and other FODMAPs are common but often poorly recognized and managed. These intolerances can manifest as unexplained bloating, belching, distension, gas, abdominal pain, or diarrhea. Carbohydrate intolerance can lead to unexplained gastrointestinal symptoms such as abdominal bloating, gas, flatulence, pain, distension, nausea and diarrhea.
Fructose: A Closer Look
Fructose, a 6-carbon monosaccharide, is naturally present in fruits, vegetables, and honey. It is also produced enzymatically from corn as high-fructose corn syrup (HFCS), a common ingredient in sweeteners and soft drinks. Humans have a limited absorptive capacity for fructose, and malabsorption can lead to osmotic effects and gas production in the colon.
Breath Testing for Carbohydrate Intolerance
Breath testing after ingesting fructose has been widely adopted as a standard method of identifying fructose malabsorption and intolerance. During testing, both H2 and CH4 should be analyzed from the breath samples that are collected every 30 minutes for up to 3 hours. Presence of malabsorption and reproduction of symptoms during a breath test provides the best objective evidence and symptom correlation for fructose intolerance that can then lead to a firm diagnosis, and this helps avoid the use of empirical or unnecessarily restrictive diets.
Dietary Management of Fructose Intolerance
There are no established protocols or guidelines in the dietary management of fructose malabsorption or intolerance and therefore management depends on the centerâs experience. Patients with fructose intolerance undergo an "elimination phase," restricting fructose intake to approximately 5 g per day for about 2 weeks. Once symptoms improve, a "re-introduction phase" begins, where small amounts of higher fructose-containing foods are gradually added back to determine individual tolerance levels.
Fructans: Oligosaccharides and Polysaccharides
Fructans are oligo- or polysaccharides consisting of short chains of fructose units with a terminal glucose molecule. The human body has limited ability to break down these oligo- or polysaccharides in the small bowel and only absorbs 5 â 15% of fructan. The mechanism for malabsorption and intolerance is related to the lack of enzymes to fully hydrolyze glycosidic linkages in the complex polysaccharide, and therefore results in the malabsorbed fructans to be delivered to the colon, which are then fermented.
Diagnosing Fructan Intolerance
At the moment, there is no standardized test for a diagnosis of fructan intolerance. There are only a few studies on absorptive capacity of fructan in humans. A preliminary report suggests that a dose of 7.5 g may be the optimal dose for breath testing of up to 3 hours in fructan intolerance. A composite index, Fructan Intolerance Index (FII) that is a change of ⥠20 ppm over baseline of H2 and or CH4 along with abdominal symptoms during the test was found to best characterize fructan intolerance.
Dietary Management of Fructan Intolerance
There are no clear guidelines on dietary management in fructan intolerance since there are no robust published data. As with other carbohydrate intolerance, identification and elimination of problematic foods containing fructan is the principle approach. In any case, involvement of an interested dietitian is paramount.
FODMAPs and IBS
FODMAPs have an additive effect on symptoms in patients with IBS and therefore, total FODMAPs intake becomes important. However, some people may be more sensitive to some groups. Many patients with IBS have visceral hypersensitivity, which could be triggered by abrupt luminal distension.