Malabsorption

Symptoms of malabsorption

The most common sign of malabsorption is chronic diarrhoea. If you're not absorbing fat properly, your stools may also be:

• pale, bulky, greasy and unusually foul-smelling (called steatorrhoea)
• difficult to flush away, or floating in the toilet bowl.

If you struggle to absorb certain sugars, you might instead notice bloating, wind and sudden, explosive diarrhoea. Whatever the cause, you'll often lose weight or find it hard to maintain your weight, even if you're eating enough.

Over time, malabsorption can also cause signs of specific nutrient deficiencies, such as:

• tiredness and weakness, from a lack of iron, folate or vitamin B12
• swelling, dry skin and hair loss, from a lack of protein
• bone pain or weak bones, from a lack of calcium or vitamin D
• bleeding gums or easy bruising, from a lack of vitamin C or vitamin K
• a tingling, pins-and-needles sensation, from a lack of vitamin B1 or B12.

In women, malabsorption can also cause periods to stop.

Causes and risk factors

Malabsorption happens when something interferes with digesting your food, absorbing nutrients into your bloodstream, or both. Causes generally fall into a few broad groups:

• digestive enzyme problems, such as pancreatic diseases or lactase deficiency (lactose intolerance)
• damage to the lining of your small intestine, from conditions such as coeliac disease, Crohn's disease, infections, or long-term alcohol use
• reduced bile production, from liver, gallbladder or bile duct disease, which affects how well you absorb fats
• an overgrowth of bacteria in the small intestine, or too little stomach acid
• surgery that removes part of your small intestine, reducing the area available for absorption
• conditions affecting your lymphatic system, which can specifically affect fat absorption.

A short-term episode of malabsorption can also follow a bout of gastroenteritis (a stomach bug) and doesn't usually need specific treatment. Ongoing malabsorption is more likely if you have a long-term digestive condition, and it can be harder to spot in older adults than in children, who have higher nutritional needs and may not be able to describe their symptoms.

Types of malabsorption

Malabsorption is usually grouped by which nutrient is affected:

• fat malabsorption, the most common type, which also affects your ability to absorb the fat-soluble vitamins A, D, E and K
• carbohydrate malabsorption, such as lactose intolerance, which mainly causes gas, bloating and diarrhoea rather than malnutrition
• protein malabsorption, which is uncommon on its own, and usually linked to a specific intolerance such as gluten
• bile acid malabsorption, where bile salts that should be reabsorbed pass into your colon instead, causing chronic, watery diarrhoea.

Some conditions, such as coeliac disease and inflammatory bowel disease, cause general malabsorption, affecting your ability to absorb most or all nutrients, rather than just one.

Diagnosing malabsorption

Your doctor will start by asking about your symptoms, your diet and your medical history, and will examine you. Chronic diarrhoea, weight loss, anaemia or other signs of a nutrient deficiency will raise suspicion of malabsorption, though it can be harder to spot in older adults.

Tests to confirm malabsorption and find its cause may include:

• a stool test, measuring the amount of fat in your stools over several days, since more than 7g of fat a day points to malabsorption
• blood tests, to check for specific vitamin, mineral or nutrient deficiencies, and markers of conditions such as coeliac disease
• a breath test, to check for lactose intolerance or bacterial overgrowth in your small intestine
• a sweat test, specifically to check for cystic fibrosis
• imaging tests, such as a video capsule endoscopy, CT scan or barium X-ray, to look at your digestive organs
• a biopsy of your small intestine, taken during an endoscopy, to check for damage to its lining.

Treating malabsorption

Treatment depends entirely on what's causing your malabsorption but often combines correcting any nutrient deficiencies with treating the underlying cause.

• avoiding a specific food, such as lactose or gluten, if a food intolerance is the cause
• replacement digestive enzymes, for example if your pancreas isn't producing enough
• vitamin, mineral or other nutrient supplements, taken as tablets, or, if needed, by feeding tube or directly into a vein
• antibiotics, for infections or bacterial overgrowth
• medicines to bind excess bile acids, if bile acid malabsorption is causing your diarrhoea
• surgery, in some cases, for example to remove an obstruction or, rarely, an intestinal transplant for severe, long-term cases.

Some causes, such as a mild food intolerance, may need nothing more than a change to your diet, while chronic underlying diseases will need more specific, ongoing treatment. Working with a dietitian can help you get the nutrition you need while managing your symptoms, and you'll usually have follow-up appointments to check the treatment is working.

When to see a doctor

See a doctor if you have ongoing diarrhoea, unexplained weight loss, or persistently pale, greasy or foul-smelling stools that are hard to flush away, especially if these last more than a few weeks.

Get medical advice sooner if you also have signs of a nutrient deficiency, such as unusual tiredness, bruising or bleeding easily, numbness or tingling, or bone pain, since ongoing malabsorption can lead to serious complications if it isn't treated.