Types of lactose intolerance

A trial of a two-week period of a strict lactose-free diet, with careful attention to food labels, should be tried. If symptoms resolve but recur on re-introduction of lactose-containing foods, the diagnosis can be made.

There is no single agreed diagnostic test but the following can be used where appropriate:

  • A lactose tolerance test involves a test dose of 2 g of lactose per kg body weight up to a maximum of 50 g, given after a fast, and noting the rise in blood glucose, rather like a glucose tolerance test. A positive test is reproduction of symptoms and rise in serum glucose by <1.11 mmol/L, 60-120 minutes after ingestion. However, this rather higher dose than is presented in a normal meal has been criticised as representing an atypical situation. This has now been superseded by breath hydrogen tests.
  • Breath hydrogen test – if carbohydrate is unabsorbed in the gut, it is fermented by bacteria in the large intestine and hydrogen gas is produced, absorbed into the blood and excreted by the lungs. Thus, carbohydrate malabsorption can be determined by measuring the exhaled hydrogen concentration after a carbohydrate load. Normally, the fermenting bacteria are confined to the large intestine but, when bacterial overgrowth in the small intestine occurs, upper small bowel fermentation of ingested lactose occurs and causes an early rise in the exhaled hydrogen concentration. There will still be a later rise in exhaled hydrogen during large bowel fermentation. Antibiotics may produce false negative results. For diagnosis of lactose intolerance, 0.5-1.0 g/kg to a maximum of 12-25 g of lactose is given and an increase greater than 20 ppm of hydrogen is diagnostic.
  • Genetic tests are available but so far cannot cover all the genetic mutations that exist within different populations.
  • If difficulty remains, a small intestinal mucosal biopsy can be obtained by endoscopy for direct assay of lactase activity as well as that of other brush border disaccharidases. The gold standard test is analysis of enzyme and carbohydrate levels and ratios from biopsy; however, it is usually too invasive a test for a mild condition.

Differential diagnosis

  • Recurrent abdominal pain of childhood.
  • Irritable bowel syndrome.
  • Allergy to milk proteins or other constituents of milk.
  • Deficiency of other disaccharidases.
  • Infantile colic.
  • Diverticular disease.
  • Ulcerative colitis.
  • Coeliac disease.
  • Cystic fibrosis.


Avoiding milk and dairy products will relieve symptoms in most. However, lack of milk and dairy products can result in the loss of a vital source of calcium, especially if the person is on a vegetarian diet. Furthermore, a 2010 systematic review concluded that most people with the condition could tolerate a glass of milk per day.

Primary lactase deficiency

  • Varying amounts of lactose can be tolerated – this needs to be determined. Things can be further improved by taking the lactose in divided portions throughout the day and with meals.
  • Yoghurt and curds may be tolerated due to thicker consistency, slower gastric emptying and because their preparation means that the lactose is partially hydrolysed. Live yoghurts contain bacteria which partly hydrolyse their own lactose.
  • Dairy products with a higher fat content, such as ice cream, chocolate milk, cheese, and full-fat rather than skimmed milk, are better tolerated. The fat content slows gastric emptying.
  • Hard cheeses, such as Cheddar, Edam, Parmesan and Emmental, contain very little lactose and may be well tolerated.
  • Milk substitutes can also be used but they contain fewer nutrients compared with cow’s milk.
  • Lactase enzyme preparations available commercially from health food shops can be combined with lactose foods but these are expensive and the evidence of efficacy is variable.

Secondary lactase deficiency

  • Resuscitation with intravenous rehydration may occasionally be required in secondary lactase deficiency.
  • Antibiotics should be avoided unless there is strong evidence for a bacterial cause.
  • Parents/carers should be advised to continue giving formula or breast milk or regular milk during an acute diarrhoeal illness in most cases. Alternative preparations may be considered in higher-risk cases, such as infants younger than 3 months, or malnourished children.

Developmental lactase deficiency

Tube feedings with milk containing lactose in premature infants usually contain breast milk, or if not possible, reduced-lactose milk. Full-strength lactose formula is more likely to induce intolerance. Evidence for adding lactase to feeds in this time period remains weak. Breast milk contains components which aid lactose absorption.

Congenital lactase deficiency

Babies with severe deficiency require a diet full of essential nutrients but excluding lactose.They cannot be breast-fed; they need lactose-free formula milk and must be weaned on lactose-free foods.


Most people with lactase deficiency suffer very little. Transient lactase deficiency affects a significant number of infants following severe gastroenteritis. Improper early feeding with lactose-based products without the recognition of lactose malabsorption can lead to chronic diarrhoea and malnutrition.

Lactose enhances the absorption of several minerals, including calcium, magnesium and zinc. In addition, milk products are high in calcium that is extremely important in bone growth. Children can quickly become deficient and so calcium supplements are required if there is restriction of eating dairy products.


The following may contain unexpected lactose and patients and carers need to be advised to monitor food labels:

  • Bread.
  • Cakes.
  • Cereals.
  • Margarine.
  • Dressings.
  • Sweets.
  • Snacks.
  • Various drugs, whether prescribed or over-the-counter.


Lactose intolerance

Complications of lactose intolerance

Milk and other dairy products contain calcium, protein and vitamins, such as A, B12 and D.

Lactose also helps your body absorb a number of other minerals, such as magnesium and zinc.

These vitamins and minerals are important for the development of strong, healthy bones.

If you’re lactose intolerant, getting the right amount of important vitamins and minerals can prove difficult.

This may lead to unhealthy weight loss and put you at increased risk of developing the following conditions:

  • osteopenia – where you have a very low bone-mineral density; left untreated, it can develop into osteoporosis
  • osteoporosis – where your bones become thin and weak, and your risk of breaking a bone is increased
  • malnutrition – when the food you eat does not give you the nutrients essential for a healthy functioning body; this means wounds can take longer to heal and you may start to feel tired or depressed

If you’re concerned that dietary restrictions are putting you at risk of complications, you may find it helpful to consult a dietitian.

They can advise you on your diet and whether you require food supplements.

Your GP should be able to refer you to an NHS dietitian free of charge. Or you can contact a private dietitian.

The British Dietetic Association has information on how to find a private dietitian.

The incapacity to break down lactose which is a natural type of sugar is known as lactose intolerance. Mostly, lactose is available in milk products like yogurt and dairy. You will become lactose intolerant if your small intestines seize to generate sufficient lactase enzyme needed to break down and digest the lactose. The lactose which has not been digested goes to the colon when this occurs. It then interacts with the bacteria found in the colon and results in symptoms like diarrhea, bloating and gas. Lactase deficiency is another term used for lactose intolerance.

Adults suffer most from lactose intolerance especially in Africa, Asia, the Mediterranean and the Americas. Approximately 20 million individuals from America who are 20 years old and above suffer from lactose intolerance. Although it is unlikable, lactose intolerance is not a severe condition.

Have a question aboutLactose Intolerance?Ask a doctor now

After thirty minutes to two hours of consuming dairy, lactose intolerance normally leads to gastrointestinal symptoms like diarrhea, bloating and gas. Individuals suffering from lactose intolerance may take drugs that have lactase, before consuming dairy or to avoid dairy consumption.

Forms of lactose intolerance

Lactose intolerance has three main forms and each has a distinct cause.

Primary lactose intolerance

This kind of lactose intolerance is the most widespread.

Many individuals have sufficient lactase at the time they are born. To be able to digest breast milk, infants require the lactase enzyme. With time, the quantity of lactase an individual generates goes down. The reason for this is that people’s diets becomes diverse and depends less on dairy as they continue to age.

The lactase reduction is normally slow and particular regions of the world are more susceptible to lactose intolerance than others.

Secondary lactose intolerance

Lactose intolerance can also be as a result of surgery, celiac disorder, injury of the small intestines, or a inflammatory bowel disorder. If the main condition is properly treated, you may regain your lactase levels.

Congenital lactose intolerance

Although it is not very common, you may inherit lactose intolerance. A child can inherit a malfunctioning gene from the parents and this can lead to the total lack of lactase production.

Babies born in these cases are not tolerant of milk. Once breast milk or formula that has lactose is given to the baby, diarrhea will occur. This condition can be fatal if it is not diagnosed and cured early on. There can be loss of electrolytes or dehydration as a result of diarrhea. Introducing formula without lactose will simply cure this condition.

Developmental lactose intolerance

When an infant is born premature, this rare type of lactase intolerance can occur. The reason for this is because babies start generating lactase when the pregnancy nears its end.

Lactose intolerance symptoms

These symptoms can either be severe or mild. They include:

  • Nausea
  • Cramps in the abdomen
  • Gas
  • Diarrhea
  • Bloating

Treatment of lactose intolerance

There is no method to make the body generate extra lactase. Lactose intolerance is treated by either cutting dairy or lowering the amount you consume.

Dairy products that do not contain lactose can be purchased at many supermarkets. You can still consume certain hard cheeses like swiss, cheddar and parmesan. Yogurt is also a good option.

You can buy lactase enzymes in form of drops, capsules and pills and consume them before taking dairy. The drops are then added to milk.

Lactose intolerance: What you need to know

Most milk and milk products have lactose in them, and many processed foods have milk and dairy products added to them.

Any product with milk, lactose, whey, curds, milk by-products, dry milk solids or non-fat dry milk powder listed in their ingredients will have lactose in them.

Foods that commonly contain lactose include:

  • cakes and biscuits
  • cheese sauce
  • cream soups
  • custard
  • milk chocolate
  • pancakes
  • scrambled eggs
  • quiche

A person with a lactose intolerance should check food labels carefully, as some foods may contain “hidden lactose.”

Examples include:

  • muesli bars
  • breads
  • breakfast cereals
  • margarine
  • some instant soups
  • boiled candies
  • chocolate candies and bars
  • some processed meats, such as sliced ham
  • salad cream, salad dressing, and mayonnaise

Ingredients to look out for on a label include milk solids, non-fat milk solids, whey, and milk sugar.

Around 20 percent of prescription medications, such as birth control pills and around 6 percent of over-the-counter drugs, for example, treatments for stomach acid, contain lactose.

People with a severe lactose intolerance should tell their doctor or pharmacist about this when obtaining new medications.

Alternatives to dairy milk include almond, flax, coconut, or soy milk. Grocery stores often stock a range of lactose-free alternatives to various products.

It is safe for women with a lactose intolerance to breastfeed an infant. It will not make the infant sick or increase the risk of intolerance, and breast milk has important benefits for growth and development.

Alternatives to dairy

In many societies, dairy products are an important source of calcium, protein, vitamins A, vitamin B12 and vitamin D. Cutting out dairy products may lead to malnutrition, unless they are replaced with foods of similar nutritional content.

Share on PinterestAlmond or soy milk are suitable for people who are lactose intolerant.

Alternative sources include:

  • Calcium: Seaweeds, nuts and seeds, blackstrap molasses, beans, oranges, figs, quinoa, amaranth, collard greens, okra, rutabaga, broccoli, dandelion leaves, kale, and fortified products such as orange juice and plant milks
  • Vitamin A: Carrots, broccoli, sweet potatoes, cod liver oil, liver, spinach, pumpkin, cantaloupe melon, egg, apricot, papaya, mango, and peas
  • Vitamin D: Levels can be enhanced by exposure to natural sunlight, consuming fatty fish, eggs, fish liver oils, and some fortified plant milks and other fortified products
  • Lactose-free milk: A person with severe symptoms should check the label to ensure that lactose levels are zero, and not just reduced. Vegetable-based milks also contain less protein than cow’s milk

According to Nutrition Australia, most people with lactose intolerance do not need to avoid all dairy products.

Even those with low lactase levels can normally tolerate up to 12 grams of lactose a day, they say, or one cup of milk. Spreading consumption throughout the day, and taking it with meals, can increase tolerance.

Anyone who is considering changing their diet should first consult a doctor or a registered dietitian for advice.

Lactose intolerance can be a very sneaky allergy. The symptoms can be caused by many other illnesses, and we sometimes forget that something as simple as dairy could be the cause. It can all be a bit confusing, so we’ve put together an easy guide on what lactose intolerance is and how to tell if you are lactose intolerant.

Alright, first up – what is lactose intolerance?

So what causes lactose intolerance? In the lining of your small intestine is a lactase enzyme. This enzyme has the simple job of turning milk sugar into an absorbable compound. However, those who have lactose intolerance do not produce enough of the lactase enzyme, which causes the lactose to move past the small intestine without being properly digested. It then travels to the large intestine where bacteria partially breaks it down into acids and gasses, which then causes some of the lactose intolerance symptoms, such as gas. Any more undigested lactose continues along the intestinal tract which attracts water molecules and causes further symptoms such as diarrhea.

Symptoms of lactose intolerance

Now that you understand the basics of how it works, these are the symptoms to look out for:

  • abdominal pain
  • abdominal swelling (bloating)
  • flatulence (excessive wind)
  • Diarrhoea
  • Nausea

How to test if you’re lactose intolerant at home

Once you suspect that you have lactose intolerance, you can either go straight to the doctor. Or you can try a couple of things yourself before heading to the doctor.

  • Try eliminating dairy from your diet to see if the symptoms persist. Symptoms normally begin 30 minutes to 2 hours after consuming dairy. You can then reintroduce dairy back into your diet to see if the symptoms come back.
  • Track your symptoms, track all the symptoms you’re experiencing as well as if you’ve had any dairy before the symptoms started and roughly when the dairy was consumed. You can track all your symptoms, along with pictures, notes, times, and dates, with our health app Wanngi, which creates a visual timeline that can help you and your doctor easily see what’s happening with your health.

  • Another simple test you can do is to try lactose free milk instead of regular, and see if your symptoms persist.

How your doctor will test to see your lactose intolerance

When you go to the doctor you can explain your symptoms, or show them with Wanngi to help with your diagnosis. If your doctor believes that you have lactose intolerance then they may proceed with various tests, some of which include:

  • The Hydrogen Breath Test, when lactose is broken down by bacteria in the large intestine, it creates more hydrogen. This test measures the amount of hydrogen that you breathe out.
  • Elimination Diet, which is what we previously discussed in our self administered tests section.
  • Blood Glucose Test, which estimates your body’s ability to process lactose by measuring the glucose in your blood.

Lactose intolerance do’s and don’ts

A version of this post first appeared on Dr. Ayala’s Open Salon blog.

Are most Americans lactose intolerant? Do all dairy products contain lactose? How critical is it to stick to a lactose-free diet?

Although most of us know someone who is lactose intolerant, and “lactose intolerance” frequently comes up in health-related conversations, there are many myths and misconceptions regarding this common digestive issue. I’d like to take a look at this malady and at the findings of a recent National Institutes of Health (NIH) consensus conference on lactose intolerance, where experts in many medical fields pored over the relevant medical literature, discussed findings and developed a state-of-the-science statement that includes a few surprises.


(This post is about the common form of lactose intolerance — primary lactose intolerance — and is not about lactose intolerance that arises from illness or intestinal injury, or the rare cases of babies born unable to digest lactose.)

Lactose and lactose intolerance

Chemistry moment (this won’t take long): Lactose is a two-molecule sugar (or disaccharide) made up of one molecule of glucose and one molecule of galactose. In order to absorb lactose our body needs to break the bond between the two simple sugars using the enzyme lactase.


Lactase is abundant in the human intestine in infancy, but its level declines with age in many people. Lactase production is a fascinating example of our body’s ability to turn genes on and off; while the genetic code for producing lactase is in the cell, the cell can turn off production partially or completely.

Those of us with lower levels of lactase don’t break up some or all of the dietary lactose, which will reach the large intestine undigested; there, bacteria will happily feast on the sugar and produce gasses: carbon dioxide, hydrogen and methane. Undigested sugars can also draw water from the intestinal walls, causing bloating and diarrhea.

But low lactase by itself doesn’t define lactose intolerance; most people who have low lactase don’t experience signs and symptoms (the common ones being diarrhea, abdominal pain, gas, bloating or nausea). Only people with both low-lactase levels (measured by a health professional) and associated signs and symptoms have, by definition, lactose intolerance.


How common is it?

Surprisingly, the NIH panel concluded that we don’t really know.

Many people with low levels of lactase have no symptoms. Many people with gastrointestinal symptoms attribute symptoms to lactose intolerance even if they haven’t demonstrated deficiency of lactase; their symptoms may very well be due to other reasons.


What we do know is that low lactase varies across ethnic groups, occurs less frequently in European Americans and more frequently in African-Americans, Asian Americans and Native Americans.

Do people with lactose intolerance need to avoid lactose?

Let’s start with an explanation of the big difference between lactose intolerance and serious food allergies or gastrointestinal immune diseases such as celiac.


Food allergies can cause life-threatening systemic reactions after exposure to minute amounts of the offending food. Likewise, the intestine of a celiac patient suffers changes to its surface — changes that can lead to malabsorption, anemia and even cancer — even if exposed to very small amounts of gluten.

But not absorbing some of the sugars in our food is part of everyday life for all of us.

Beans, for example, contain sugar chains — called raffinose oligosaccharides — which no human can break down. The sugar polymers are digested by bacteria in the gut resulting in the well-know bean-related flatulence — the butt of many jokes — and can also cause symptoms resembling those of lactose intolerance.


Some people experience no discomfort after eating beans while others limit their intake of beans because large amounts cause them symptoms. There are even individuals who experience such great discomfort that they choose not to eat beans at all. Our individual anatomy and physiology, our intestinal microbial flora, as well as the way we perceive pain and social awkwardness differs a lot. And by no means are beans unhealthy — they are in fact very good to eat!

Milk contains a considerable amount of lactose, much more than the undigested sugars in beans, but the bean analogy can perhaps explain some of the symptom variability we see with lactose intolerance.

Lactose sources

Milk products vary greatly in their lactose content.


Milk itself has a lot of lactose, but aged cheeses have very little (most of the lactose is drawn away in the whey, and what’s left in the curd is fermented by bacteria and mold). Yogurt with live cultures contains bacteria that break down lactose, and therefore causes fewer symptoms. Butter and full-fat cream cheese contain almost no lactose.

So how much milk can people with lactose intolerance tolerate?

The NIH panel looked at the best studies, and concluded that most lactose-intolerant individuals can take in 12 grams of lactose (the equivalent of one cup of milk) in a single sitting with minimal or no symptoms and can tolerate larger amounts if the lactose if ingested with meals or spread over the day. A quart of milk (50 grams of lactose) ingested without food in one sitting will induce symptoms in most lactose-intolerant people. There’s also some evidence showing that the body gets used to lactose, and can tolerate more lactose if routinely exposed to it.

The most important long-term health consequence of lactose intolerance may be calcium deficiency


There are many ways to eat healthy, and dairy is by no means necessary for a balanced diet. Balanced Asian-type and vegan diets are perfectly healthy with little or no dairy. Calcium sources — both naturally occurring or in supplements — are plentiful. (Foods rich in calcium include collard greens, turnip greens, kale, bok choy, soybeans, okra, broccoli, some fish, cultured soy yogurt, tofu, almonds, and calcium-fortified orange juices, soy milks and cereals.)

But dairy products are by far the most prevalent — and least expensive — source of calcium in the Western diet. Since many people with real or perceived lactose intolerance avoid dairy products, they may consume inadequate amounts of calcium and vitamin D (which is added to milk), leading to weaker bones and osteoporosis.

Therefore the diagnosis of lactose intolerance should be made judiciously, and the treatment plan should include assuring that dairy avoidance, if necessary, won’t lead to nutritional deficiencies.

Practical tips:


If you think you have lactose intolerance:

  • Talk it over with your doctor; getting an accurate diagnosis for your symptoms can be important. Some of the causes of recurrent abdominal pain are treatable and it’s not a good idea to commit to an elimination diet for the wrong reason.

If you do have lactose intolerance:

  • Find a reduced-dairy eating plan that controls your symptoms, while enabling both good nutrition and enjoyment of food.
  • Eat dairy products with less lactose (cheese, yogurt) and spread your dairy consumption throughout the day. Consume dairy as part of a meal.
  • Make sure you get enough of the nutrients usually found in dairy, especially calcium.
  • Consider using lactase products; these are dietary supplements that help digest lactose.
  • Above all, listen your body — treatment and diet plans can’t ever be one size fits all. Find what works for you and stay healthy!

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