How Digestion and Absorption Work

Digestion can be disturbed at any step. Examples include a lack of an enzyme (for instance lactase, which digests milk sugar, so lactose intolerance causes gas and loose stools after dairy), too little pancreatic enzymes or bile, damage to the lining of the small intestine (as in coeliac disease, where gluten triggers the immune system to injure the gut), infections, medicines, surgery that removes or bypasses part of the gut, and changes in how fast food moves. Eating very quickly, large fatty meals, and stress can also trigger symptoms without any disease. Many symptoms come from the gut being over-sensitive rather than damaged.

Everyone digests food, and digestive symptoms are very common. In a large survey of people in 33 countries (the Rome Foundation Global Study, published in 2021), about four in ten adults met the criteria for at least one functional gut disorder, meaning a disorder of how the gut works rather than one with visible damage. Problems with actual absorption (malabsorption) are much less common but are important to recognise.

Lactose intolerance and coeliac disease are both recognised in Saudi Arabia, and iron and vitamin D deficiencies are common in the region, so a blood test is a sensible step if you have ongoing symptoms. Traditional meals such as kabsa, harees, jareesh and foul are generally well tolerated and offer rice, wheat, legumes and protein; very large, late-night family meals and fried samboosa in large amounts can trigger reflux and bloating. During Ramadan, eat iftar gradually (dates, water, then a main meal) rather than all at once, and keep a lighter, higher-fibre suhoor.

Your doctor starts with your story: what you eat, when symptoms occur, stool pattern, weight, medicines and family history. Blood tests may look for anaemia, low iron, vitamin B12 or vitamin D, and coeliac disease antibodies. Stool tests can check for infection, inflammation (such as faecal calprotectin) or pancreatic enzyme output. Breath tests are sometimes used for lactose intolerance, though their results need careful interpretation. Endoscopy (a camera test of the upper gut with small tissue samples called biopsies) and colonoscopy look directly at the lining. A food and symptom diary kept for two weeks is often very helpful.

Everyday habits shape how comfortable your digestion is.

• Eat slowly and chew well; put the spoon down between mouthfuls. Eating fast leads to swallowed air and larger lumps to digest.

• Have regular meals rather than very large ones; smaller portions are easier on the stomach.

• Leave about two to three hours between your last large meal and lying down, especially if you get heartburn.

• Keep moving. A walk after a meal helps food and gas to move on.

• Do not smoke, and keep alcohol low or avoid it; both irritate the gut and affect the liver and pancreas.

• Keep a simple food and symptom diary for two weeks before your appointment.

A varied diet built on vegetables, fruit, whole grains, legumes, fish and modest portions of meat supports normal digestion. Do not cut out whole food groups without advice.

• Increase fibre slowly, with enough fluids, to avoid gas and cramps.

• If dairy causes symptoms, try smaller portions, or fermented dairy such as laban or yoghurt, which many people with lactose intolerance tolerate better. Keep other calcium sources in your diet.

• Go easy on very fatty, fried or very spicy meals if they trigger pain or reflux.

• Do not start a gluten-free diet before being tested for coeliac disease; stopping gluten first can make the tests unreliable.

• Ask your doctor or dietitian before restricting foods for a long time, especially in children.

Medicines and supplements are used only for a defined cause. Please do not self-treat for long periods.

• Pancreatic enzyme capsules are prescribed when the pancreas does not make enough enzymes; they are taken with meals under medical guidance.

• Lactase products may help some people with lactose intolerance; ask your pharmacist or doctor.

• Vitamin or mineral supplements (iron, B12, vitamin D) are given when a deficiency is proven by a blood test.

• Over-the-counter digestive remedies and herbal products can have side effects or interact with medicines. Tell your doctor about everything you take.

Tests are chosen according to your symptoms and warning signs, not routinely for everyone.

• Upper endoscopy with biopsies can look at the stomach and the first part of the small intestine and test for coeliac disease or infection.

• Colonoscopy examines the colon when there is bleeding, a lasting change in bowel habit or anaemia.

• Breath tests and stool tests are non-invasive ways to look for lactose intolerance, inflammation or enzyme problems.

• Imaging such as ultrasound or CT looks at the liver, gallbladder and pancreas if these are suspected.

The overall picture is based on standard physiology and on guidelines for specific problems. The Rome IV criteria (Rome Foundation, 2016) define functional gut disorders, and the Rome Foundation Global Study (Sperber et al., Gastroenterology, 2021) describes how common they are. The American College of Gastroenterology guideline on coeliac disease (2023) and the American Gastroenterological Association guidance on malabsorption and on pancreatic insufficiency set out when and how absorption problems should be tested for. Evidence for popular ideas such as "food combining" or "digestive enzyme supplements" for healthy people is limited, and these are not recommended as routine.

For most people with occasional digestive symptoms, simple changes in how and what they eat bring clear improvement. If a specific cause such as coeliac disease, lactose intolerance or enzyme deficiency is found, targeted treatment usually restores comfortable digestion and good nutrition. Early assessment of warning signs allows serious conditions to be found at a more treatable stage.

• Could my symptoms be a problem with absorption rather than just sensitive digestion?

• Which tests do I need, and do I need an endoscopy or colonoscopy?

• Should I be tested for coeliac disease or lactose intolerance before changing my diet?

• Do I need vitamin, iron or B12 tests or supplements?

• Can you refer me to a dietitian?

This guide comes from the Saudi Gastroenterology Association (SGA) patient library, prepared by the Approved for publication by SGA; individual clinician review is ongoing. Last reviewed: 2026-04-24. It is for education and does not replace your doctor's advice.