Digestion after 40: what changes and what to watch for

Turning 40 does not change your digestion overnight. But several digestive problems become more common with age, many people start taking regular medicines that can affect the gut, and bowel cancer screening becomes relevant. This guide covers what the US National Institutes of Health (NIH) and the UK's National Health Service (NHS) describe, and the warning signs that deserve a doctor's attention.

What becomes more common with age

Constipation. About 16 in 100 adults have symptoms of constipation, the US National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK) says, rising to about 33 in 100 among people aged 60 and over. The National Institute on Aging (NIA) explains that many medical conditions common in older adults can play a part, including diabetes, stroke and Parkinson's disease, as can medicines (see below), low fibre, too little fluid and less physical activity. There is no "right" number of bowel movements, it adds: being regular means different things for different people. Our guide to constipation covers it in detail.

Pouches in the bowel wall. Diverticulosis, where small pouches form in the wall of the large intestine, is common with age. NIDDK reports it in more than 30% of US adults aged 50 to 59 and more than 70% of those over 80. Most people with it never have symptoms, and fewer than 5 in 100 develop inflammation of the pouches (diverticulitis).

Hiatus hernia and reflux. In a hiatus hernia, the upper part of the stomach pushes up through the diaphragm into the chest. MedlinePlus, from the US National Library of Medicine, says the risk goes up with age, obesity and smoking, and that it often occurs in people over 50. NIDDK notes that a hiatus hernia can make reflux more likely or worse. Our guide to eating late and digestion covers heartburn and reflux.

Dairy. In people whose bodies make less of the enzyme that digests lactose after infancy, levels of that enzyme get lower with age, according to NIDDK, and symptoms may not begin until later childhood, the teenage years or early adulthood. Our guide to lactose intolerance explains what that means.

Vitamin B12. Some people over 50 have trouble absorbing the vitamin B12 found naturally in food, NIA says. It is found in meat, fish, poultry and milk, and in fortified cereals. If you are concerned, talk to your doctor.

Medicines and your gut

NIA notes that older adults often have several health conditions and take several medicines, which raises the risk of side effects. Some affect the gut directly:

• Constipation. NIA lists some antidepressants, antacids containing aluminium or calcium, some allergy medicines (antihistamines), certain painkillers, some blood pressure medicines, diuretics, and iron among the causes.
• Stomach ulcers and indigestion. Regular use of anti-inflammatory painkillers (NSAIDs) such as ibuprofen is one of the main causes of stomach ulcers, and the risk of an ulcer goes up as you get older, the NHS says. It advises not taking ibuprofen or aspirin unless it has been prescribed for you, and talking to a pharmacist or GP if you take them, because they can make indigestion worse.
• Reflux. NIDDK lists NSAIDs, some blood pressure medicines (calcium channel blockers), some sedatives and some antidepressants among the medicines that can cause or worsen reflux.

NIA's advice: keep an up-to-date list of everything you take, including medicines bought without a prescription and vitamins, and show it to every doctor and pharmacist you see. If you have side effects, do not stop a medicine before talking to your doctor.

Fibre, fluids and activity

The basics do not change with age. The NHS recommends 30g of fibre a day for adults, from a variety of foods, and 6 to 8 cups or glasses of fluid a day as a guide. NIA advises plenty of natural fibre from fruit, vegetables and whole grains, enough fluids, and staying active, for example by going for walks.

For activity, the NHS recommends that adults aim for at least 150 minutes of moderate activity a week, plus strengthening activities on at least 2 days a week. From 65, it adds activities that improve balance and flexibility, and suggests being active every day, even if it is just light activity, and breaking up long periods of sitting. If you have not exercised for some time, or have a health condition, speak to a GP first. Our guide to everyday habits for a healthier gut covers these habits in more detail.

Bowel cancer screening

Your risk of bowel cancer gets higher as you get older, the NHS explains. Screening looks for signs of it in people who have no symptoms, so it can be found early, when it may be easier to treat. The US Preventive Services Task Force (USPSTF) notes that nearly 94% of new cases of colorectal cancer occur in adults aged 45 or older.

The age at which screening starts, and the test used, varies from country to country. Two examples:

• England. The NHS sends a home test kit that checks a small sample of poo for blood, called a faecal immunochemical test (FIT), every 2 years to people aged 50 to 74. People aged 75 or over can ask for it.
• United States. The USPSTF recommends screening for adults aged 45 to 75, and says doctors should offer it selectively from 76 to 85, depending on a person's health, past screening and preferences.

These recommendations are for people at average risk. The USPSTF notes that risk is higher in people with a family history of colorectal cancer. Ask your doctor what is recommended where you live, and when you should start. If you have symptoms, do not wait for a screening invitation: see a doctor.

When to see a doctor

See a GP if you notice possible signs of bowel cancer, the NHS advises, such as a change in your poo that is not usual for you, needing to go more or less often, blood in your poo, bleeding from your bottom, tummy pain, a lump in your tummy, bloating, losing weight without trying, or feeling very tired or short of breath. Some of these symptoms are very common and have other causes, but it is important to get checked.

NIA also advises seeing a doctor if your bowel habits change and you have serious stomach pain, cannot pass wind, are vomiting or have a fever, have lower back pain, or if more fibre and exercise have not helped. NIDDK adds problems or pain when swallowing, vomit that contains blood or looks like coffee grounds, and unexplained weight loss.

Get medical advice urgently, the same day, if your poo is black or dark red, or you have bloody diarrhoea.

Call your local emergency number if you are bleeding non-stop from your bottom, or there is a lot of blood or large blood clots when you poo.