Introduction

Lactose intolerance, also known as lactose malabsorption, occurs when your body cannot properly digest lactose, a sugar found in dairy products. This can cause symptoms such as bloating and diarrhoea after consuming dairy. The severity of symptoms can vary from person to person.¹

If you have lactose intolerance, there are different strategies you can do to manage your intolerance such as:

• Modifying your diet to avoid dairy products
• Taking lactase supplements
• Adding probiotics to your diet¹

Understanding your own level of lactose intolerance and your lifestyle preferences can help you manage this condition effectively (3).

What is lactose intolerance?

How is lactose intolerance developed?

Lactose intolerance occurs when your body cannot digest lactose, a sugar found in animal milk and dairy products. Lactose consists of two sugars, glucose and galactose, linked together. Normally, lactose is broken down into glucose and galactose in the small intestine by an enzyme called lactase, making these sugars easier to absorb. However, some people have low levels of lactase activity, preventing the proper breakdown of lactose, which leads to lactose intolerance.¹

Signs and symptoms of lactose intolerance

Signs and symptoms of lactose intolerance are felt after eating or drinking dairy products. These can start a few minutes or a few hours after dairy intake. Some common symptoms of lactose intolerance are:

• Diarrhoea
• Bloating 
• Feeling full
• Stomach rumbling
• Stomach cramps or pain
• Feeling sick
• Vomiting
• Farting, also known as flatulence^1,2

You may also experience less common signs and symptoms of lactose intolerance:

• Headache
• Muscle and/or joint pain
• Mouth ulcers¹

Types of lactase deficiency

Primary lactase deficiency

Primary lactase deficiency is the most common type and occurs when lactase activity declines with age. Symptoms often appear in adolescence or early adulthood. This condition, also known as lactase non-persistence, can cause sudden lactose intolerance without an obvious cause like illness or disease.¹

Secondary lactase deficiency

In secondary lactase deficiency, lactase deficiency is developed because of a disruption of the environment in the small intestines. This intestinal disruption can be caused by infections, inflammations, or certain diseases such as:

• Gastroenteritis
• Coeliac disease
• Crohn’s disease
• Ulcerative colitis
• Chemotherapy
• Antibiotics treatment¹

Congenital lactase deficiency

Also known as alactasia, congenital lactase deficiency is a rare type of lactase deficiency, due to an autosomal recessive genetic disorder. This means that congenital lactase deficiency is an inherited trait passed on from the genes of the parents. Because of this, congenital lactose intolerance is usually detected after the start of breastfeeding if the newborn starts showing signs of:

• Watery diarrhoea
• Usually no vomiting
• Enough food/milk intake
• Not refusing food/milk^1,3

Early diagnosis is crucial. Babies can risk the potential of dehydration and metabolic acidosis (having too much acid in your blood), which can be life-threatening.³

Developmental lactase deficiency

Developmental lactase deficiency occurs in premature infants born before the 37th week of pregnancy. At this stage, the intestines are still underdeveloped, leading to temporary lactose intolerance due to insufficient lactase activity. This condition usually resolves as the baby matures and their intestines develop.^1,4

How do I know if I have lactose intolerance?

To determine if you have lactose intolerance, your doctor will review your medical, family, and dietary history and may perform specific tests. Keeping a food diary detailing what you eat and drink and any corresponding symptoms can help identify patterns of food sensitivity. Your doctor might advise you to avoid lactose-containing foods for a few weeks to see if symptoms improve. Additional tests may be necessary, including:

• Hydrogen breath test
• Lactose tolerance test
• Milk tolerance test^1,2

These tests help confirm lactose intolerance and rule out other conditions with similar symptoms, such as:

• Irritable bowel syndrome
• Celiac disease
• Cystic fibrosis
• Inflammatory bowel disease
• Viral gastroenteritis
• Bacterial infection¹

Who is likely to have lactose intolerance?

Lactose intolerance is common in teenagers and adults but rare in infants. Globally, about 68% of the world's population has lactose intolerance. The prevalence varies by region. Most people in Asia and Africa are lactose intolerant (63-66%). In contrast, it is less common in western and northern Europe (4-36%). In the United States, 36% of the population is affected, while in South America, the prevalence ranges from 48% in Mexico to 80% in Colombia. Ethnic and racial groups more likely to develop lactose intolerance include:

• Africans
• Asians
• African Americans
• Asian Americans
• American Indians
• Hispanics/Latinos⁴

Diagnosing lactose intolerance

To diagnose lactose intolerance, your doctor will look at your or your child’s medical, family, and dietary history and may perform a test. Keeping a food diary that details what you have eaten or drank alongside any corresponding symptoms would be helpful in identifying patterns of food sensitivity. Your doctor may advise you to avoid any lactose-containing foods for a few weeks to see if this alleviates symptoms. Extra tests may occasionally be needed. These are:

• Hydrogen breath test
• Lactose tolerance test
• Milk tolerance test^1,2

Some conditions have similar symptoms to lactose intolerance. These tests will help your doctor to confirm lactose intolerance and not another condition or to determine the cause of lactose intolerance. Some conditions that have similar symptoms to lactose intolerance are:

• Irritable bowel syndrome
• Coeliac disease
• Cystic fibrosis
• Inflammatory bowel disease
• Viral gastroenteritis
• Bacterial infection¹

How do I manage lactose intolerance?

Dietary modifications

Changing your diet to avoid or reduce lactose-containing foods and drinks can help alleviate symptoms. Depending on your level of lactose intolerance, you may still tolerate some dairy products. Simply adjusting the amount of milk you consume might be enough. Beware of "hidden lactose" in non-dairy foods. Common lactose-containing products to watch out for include:

• Soft and processed cheese
• Buttermilk
• Cream and sour cream
• Animal milk (eg. cow, goat)
• Butter and margarine
• Whey and protein shakes or powders
• Mashed potatoes
• Pancakes, waffles, cereals
• Desserts like ice cream, custard, pudding, cake
• Salad dressing and mayonnaise
• Some kinds of bread and pastries
• Some processed meats like sliced ham^1,2

Hard cheese and yoghurt have less lactose and may be tolerated by some people. Yoghurt contains probiotics that help break down lactose. Hard and mature cheeses, such as Parmigiano Reggiano, Grana Padano, and Gorgonzola, are essentially lactose-free. The longer the cheese is matured, the less lactose it contains.⁵

Lactose-free or lactase-containing alternatives to dairy products are available. "Lactose-free" products contain trace amounts of lactose, generally well tolerated. Lactase-containing products have lactose but also the lactase enzyme to help break it down. Examples include:

• Cow’s milk with lactase
• Plant-based milk from soya, rice, oats, almonds, hazelnuts, coconut, quinoa, peas, and potato
• Yogurt and cheese from these plant-based alternatives
• Foods that say ‘dairy-free’ or ‘suitable for vegans’^2,5

Understanding terms like "hidden lactose" and "lactose-free" is crucial. For most people with lactose intolerance, products with low traces of lactose are not harmful. However, those with severe lactose intolerance should be vigilant. Check food labels for lactose or its sources, such as milk, buttermilk, anhydrous butter, whey, and milk powder.⁵

Lactase supplements

Lactase supplements provide the lactase enzyme your body lacks, helping break down lactose. They come as liquid drops, tablets, or capsules to add to food or take before consuming lactose-containing products.²

Probiotics

Probiotics are live microorganisms beneficial to the intestines and digestive system. Fermented foods like yoghurt contain probiotics that may help with lactose digestion. Some microorganisms have an enzyme called β-galactosidase that aids in breaking down lactose, although their effectiveness can vary.⁵

Complications to consider

Lactose intolerance can lead to complications due to the nutritional value of milk and dairy, which are rich in vitamins, minerals, and protein. Cow’s milk is a significant source of calcium, necessary for bone strength, as well as vitamins A, B12, and D. Avoiding milk and dairy entirely can lead to:

• Osteopenia – having lower than normal bone density. This can lead to osteoporosis
• Osteoporosis – having weak and fragile bones. This makes bones prone to fracturing and breaking
• Malnutrition – not having enough essential nutrients. This can lead to tiredness and depression
• Weight loss
• Rickets in children
• Growth failure^1,2,5

Taking alternative sources of calcium, vitamins, and minerals may be needed. It is important to talk to your doctor about your or your child’s lactose intolerance.²

Summary

Lactose intolerance is the inability to break down lactose, a sugar found in animal milk and dairy products. People have different levels of intolerance to lactose. Signs and symptoms include bloating, stomach rumbling, and diarrhoea which happen after eating or drinking products containing lactose. To manage lactose intolerance, you can adjust your diet to be mindful of lactose-containing products, take lactase supplements, and incorporate probiotics into your diet. To avoid complications, It is also important to seek alternative sources of calcium and other vitamins and minerals when avoiding lactose-containing products.

If lactose intolerance develops due to an illness, it may be temporary. Recovery from the illness or condition can lead to improved lactase activity and eventual lactose tolerance. However, lactose intolerance may be more permanent if it is associated with a long-term condition.⁴