Fructose Malabsorption


A normal healthy adult can properly digest 25-50 grams of fructose per day. Many people have difficulty digesting less than that, and a few of us have difficulty digesting any fructose at all. Why?

Are apples really the problem? Has too much honey contributed the massive increase in gut problems. Why is it we are happy to eat highly processed low carb, low fat, high protein bars, yet we’re afraid of bananas?[private]

What is FM?

Fructose malabsorption, formerly known as “dietary fructose intolerance” (DFI), is a common digestive disorder that occurs due to improper absorption of fructose (and other sugars like lactose or sorbitol) in the small intestine. What results is an increased concentration of fructose in the entire intestinal tract. About 30-40% of people suffer from F.M. That’s a lot of us considering anything over 5% are considered significant.

Not to confuse F.M. with ‘fructose intolerance’ which is a rare (1 in 10,000 people) and potentially fatal condition in which the liver enzymes that digest fructose are deficient.

What is fructose?

Fructose is the major carbohydrate present in fruit, and although dietary fructose is derived from fruit, most of it comes in the form of sucrose – commonly known as ‘sugar’ – and from foods containing added sucrose. This is because sucrose consists of 50% fructose and 50% glucose. Sweet foods such as desserts, cakes, chocolate and other confectionery, and sweetened beverages such as carbonated soft drinks, sports drinks and so on, have large amounts of added fructose. High fructose corn syrup is a big problem also as it is added to many packaged foods. Fruit juice is also very high in fructose, and continues no fibre to help absorb it.

Why the problem?

Unlike other foods, fructose doesn’t satisfy hunger. So we can eat and eat and eat it past what is required or needed. Weight gain and a myriad other health issues result form an excessive intake of fructose. Issues such as chronic diseases like heart disease, type 2 diabetes and even some cancers.

Most people eat and dink more fructose than their digestive system can absorb. The majority of us cannot properly digest all the fructose we get every day from an apparently normal and healthy diet. A healthy adult can properly digest 25-50 grams of fructose per day, but many people have difficulty digesting less than that, and some of us struggle digesting any fructose at all. Fructose intake should be kept to around 3 g/serving. A can of soft drink for example contains 20-35 grams. Be mindful of the fact that Fructose-containing foods are better tolerated in several smaller servings throughout the day and not on an empty stomach.


If you eat more fructose than your small intestine can absorb, the excess fructose passes through to the large intestine. In the large intestine, the fructose prevents the absorption of water, causing watery stools or diarrhoea, and preventing the absorption of nutrients like iron and zinc. (Supplements won’t absorb either.) The displaced sugar in the large intestine also feeds the bacteria and yeasts that live there, producing hydrogen, carbon dioxide and methane. These gases create pressure in the large intestine, causing bloating, abdominal pain and flatulence.

If your digestive system is able to absorb all of the fructose, you’ll likely suffer from weight gain and obesity, liver cirrhosis, fatty liver and other symptoms of an overworked liver that are normally found in those who drink alcohol to excess. If your digestive system cannot absorb all the fructose, you’ll suffer from the fructose malabsorption symptoms described below.

The symptoms of Fructose Malabsorption have some similarities to those of Irritable Bowel Syndrome (IBS), food allergies, food intolerance, or simply feeling although you’re not digesting properly. When your digestive system doesn’t absorb fructose properly, it can cause abdominal pain, diarrhea and gas. These symptoms can also be caused by a candida overgrowth, from which around 1 in 3 people suffer. Interestingly, candida often accompanies FM.

Short Term Symptoms

Immediate symptoms that may and do occur within minutes of eating foods high in fructose. They can persist for days.

  • Flatulence, bloating and distension (from fructose fermenting in the small and large intestine).
  • Diarrhoea, and to a lesser degree constipation.
  • Indigestion, stomach pain, abdominal pain.
  • Fatigue, lack of energy.
  • Brain fog.
  • Negative and intense emotions.
  • Nausea or even vomiting if large quantities of fructose are consumed.

Long Term Symptoms

  • Sugar craving (or less frequently, sugar aversion).
  • Poor mineral and vitamin absorption causing anaemia, malnourishment and general poor health. Often B vitamins, folate, tryptophan, zinc, iron, magnesium, calcium and other vitamins and minerals will be low. Patients take supplements of these minerals and vitamins with little or no benefit, because they are not being absorbed. They eat good high-nutrient foods, but again many micronutrients in this food are not digested properly.
  • Poor skin, nails and hair.
  • Underweight, difficulty gaining weight (however, it is also possible to be overweight whilst suffering FM).
  • Being moody, early signs of depression.
  • Osteopenia/osteoporosis, which can also be caused by a diet high in fructose and low in magnesium.
  • Blood triglyceride levels raised.
  • Heart disease.
  • Inflammation in many forms, including skin problems like rashes, hives, eczema, and dermatitis etc, IBS, heart diseases.

How To Treat it?

Removing fructose from your diet can eliminate all symptoms and restore normal digestion, with health and wellbeing returning. After you have been symptom-free for about 3 months, you can gradually re-introduce small amounts of many of the whole foods that previously caused problems, one at a time. No need to re-introduce high fructose corn syrup or refined sugar of any kind. A good probiotic will naturally very beneficial also.  Fructose Malabsorption can be healed, but avoid repeating the patterns that potentially caused the problem in the first place – refined sugar.


  • Hydrogen breath test.
  • Stool test.
  • Self-diagnosis. Keep a food diary of everything you’ve consumed and then how you feel after. Keep a note of the different symptoms and when they occur. The journal is important, as the effects of some foods can take hours or even up to 3 days to present

What Foods To Avoid?

Foods that contain a high level of free fructose. Glucose helps the small intestine to absorb fructose, so if a food is high in fructose, but also contains as much or more glucose, you can usually eat it with no negative effects. Foods with a high glucose content eaten with foods containing lots of fructose may help to absorb the excess fructose.

Many common fruits contain nearly equal amounts of the fructose and glucose, so they do not present problems for those individuals with Fructose Malabsorption. Some fruits however have a greater ratio of fructose than glucose and should be avoided. These are apples, pears and watermelon – which contain more than twice as much fructose as glucose. Fructose levels in grapes vary depending on ripeness and variety, where unripe grapes contain more glucose.

  • Fruit and fruit juices: apple, cherry, grape, guava, lychee, mango, melon (honeydew and watermelon), orange, papaya, pear, persimmon, pineapple, quince, and star fruit. Cooked fruit generally has lower fructose content than uncooked fruit.
  • Most dried fruit, including currant, dates, dried fruit or health bars, fig, raisin.
  • Processed fruit: barbecue sauce, chutney, fruit from cans (often in juice), plum sauce, sweet and sour sauce, and tomato paste.
  • Berries in larger quantities: blueberry, raspberry.
  • Sweets, food and drinks with very high sucrose (table sugar) content and with high fructose corn syrup (HFCS).
  • Honey, maple syrup, agave, molasses, palm or coconut sugar, high fructose corn syrup.
  • Vegetables in larger quantities (fructan content): artichoke, asparagus, beans, broccoli, cabbage, chicory, leek, onion, peanuts, tomato, and zucchini.
  • Sweet wines: e.g. dessert wines, muscatel, port, and sherry.
  • Wheat- based products: flour, pasta, bread, and whole-grain breakfast cereals.
  • Whole-meal products in large amounts.
  • Sorbitol (E420 is sorbitol) and xylitol (E967 is xylitol) containing foods: diet / ‘light’ and diabetic drinks, sugar-free chewing gum and sweets, stone fruit, dried fruits (e.g. apple, apricot, date, fig, nectarine, peach, plum, raisin). Beer may be a problem in large amounts.
  • Inulin, (a fructan) content is high in the following foods generally known to cause bloating and gas: asparagus, dandelion leaves, garlic, leeks, and onion and wheat bran.
  • Foods containing sorbitol, present in some diet drinks and foods, and occurring naturally in some stone fruits, or xylitol, present in some berries, and other polyols (sugar alcohols), such as erythritol, mannitol, and other ingredients that end with -tol, commonly added as artificial sweeteners in commercial foods.
  • Foods high in fructans usually cause the same problems as fructose, although this is still under investigation. However, it is recommended that fructan intake for Fructose Malabsorbers should be kept to less than 0.5 grams/serving, as opposed to 0.3g/serving for fructose. Supplements with inulin and fructooligosaccharide (FOS) – both fructans, should be avoided also.
  • Foods rich in fructans and other fermentable oligo-, di- and mono-saccharides and polyols (FODMAPs), including artichokes, asparagus, leeks, onions, and wheat-containing products, including breads, cakes, biscuits, breakfast cereals, pies, pastas, pizzas, and wheat noodles.

Examples of generally well-tolerated fruit and vegetables are:

  • Eggplant, banana, Brussels sprouts, carrots, mandarin, corn, cucumber, fennel, grapefruit, lemon, potato, pumpkin, radishes, rhubarb, sauerkraut, spinach and sweet potato.


If cutting down or out foods high in fructose for 2 weeks doesn’t solve the problem, you may need to follow the stricter low FODMAP diet. FODMAPs are Fermentable Oligosaccharides (eg: fructans, galactans), Disaccharides (eg: lactose), Monosaccharides (eg: fructose) and Polyols (eg: sorbitol, mannitol, maltitol, Xylitol, isomalt etc). These food molecules may cause the same food absorption problems as fructose.

As always with gut complaints, start by addressing your lifestyle, including your stress levels – work/life balance. Eating too quickly, on the go and/or under stress will make it very difficult for your organs of digestion to function efficiently. Give them a helping hand by practicing Mindful Eating. This is eating whilst doing nothing else, and putting your food or utensils down in between each mouthful. Stop eating before you’re full, and try to eat a balanced diet high in plant- based, whole food. Once again S.L.O.W food wins – Seasonal. Local. Organic. Whole. Fructose Malabsorption is reversible.

Janella Purcell 2015[/private]




  • Lisa

    My son was recently diagnosed by a breath test for fructose malabsorption. He continues to have some symptoms after eliminating fructose containing foods. He was referred for a sucrose test, too, but was negative for that. He only had gas during that test, and felt off the rest of the day. I keep reading that table sugar is safe for him because of the 50/50 nature of the sucrose and fructose, but eating smarties or sweet tarts with meals that contain a little brown sugar or something does absolutely no good. For instance, I modified a chocolate chip muffin recipe to use only dextrose in the batter. He would have only had 6 grams of sugar from the chocolate chips, which should have been balanced, or more than balanced, by all the dextrose. While he didn’t have diarrhea he did go to the bathroom four times during the afternoon! No amount of smarties seems to cancel out reactions to ketchup on a burger. Is it possible not to tolerate much fructose, even with glucose, at all?

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