Sensitivity to dairy products and lactose intolerance is more common than you may think. The Food Intolerance Institute of Australia estimates up to 75% of the population is intolerant to dairy/lactose.

What is lactose?

Lactose is a sugar or carbohydrate naturally found in the milk of most mammals. Our bodies break down lactose using an enzyme called lactase, which is found in the small intestine. Lactase enzymes break lactose down to absorbable compounds, glucose and galactose.

Lactose is not absorbed or digested properly if your body doesn’t produce enough lactase. Undigested lactose will travel along the digestive tract to the large intestine, which is then partially broken down into acids and gases, which causes symptoms.

Lactase is particularly important for babies as they need to digest breast milk. As we grow older, our bodies produce less and less lactase, meaning we are unable to properly digest the lactose in milk and other dairy products. It is rare for people of Western European descent to develop lactose intolerance, but it is considered fairly normal in other parts of the world as people age.

Lactose intolerance can also develop temporarily after a bout of gastroenteritis, but usually improves within a few weeks. A parasitic infection can also temporarily reduce lactase levels in the body. People who have coeliac disease or Crohn’s disease can be sensitive to lactose due to damage caused to the lining of their gut.

Symptoms of lactose intolerance

Symptoms of lactose intolerance can differ from person to person, with varying severity. Symptoms are usually experienced within thirty minutes to two hours after ingesting food containing lactose.

Here are some common symptoms of lactose intolerance.

  1. Stomach pain and bloating. This occurs due to the acids and gases which are fermented in the large intestine. Stomach pain and cramps are usually located around the belly button. Bloating is caused by an increase of water and gas, which causes stretching in the gut walls. This pain or bloating can result in vomiting or nausea for some people, especially those who are particularly sensitive.
  2. Flatulence (excessive wind). The gases fermented in the large intestine include hydrogen, methane and carbon dioxide. For people who are lactose intolerant, the large intestine is very good at fermenting these gases and creates more, which increases flatulence. The amount of gas produced can vary from person to person.
  3. Diarrhoea. Lactose intolerance causes diarrhoea due to increased volumes of water in the large intestine. Most of the acids and gases fermented in the large intestine are reabsorbed, but leftover acids and gases increase the amount of water released by our bodies into the small intestine.
  4. Constipation. Constipation is rarer than diarrhoea for people who are lactose intolerant. However, the production of methane gas in the large intestine can slow down the movement of food through the gut, causing constipation.

Some of these symptoms can also be caused by an allergy to milk, which is different to lactose intolerance. People who are allergic to milk can experience vomiting and diarrhoea, rashes, eczema, hives, facial swelling, wheezing and coughing. Some people can be anaphylactic to milk, which means they may also experience trouble breathing, dizziness, or paleness and floppiness. If someone is experiencing anaphylaxis, it is important to call triple zero for an ambulance, as they may require an adrenaline injection.

I think I’m lactose intolerant, what do I do?

The home doctor experts recommend seeking a diagnosis for lactose intolerance via your GP or local healthcare professional. Symptoms can be general, so it’s important to rule out other potential issues.

There are several methods used to diagnose lactose intolerance. One method is the hydrogen breath test, which measures the amount of hydrogen produced after someone ingests lactose. Excess fermentation resulting in higher levels of hydrogen may indicate lactose intolerance. Another method of testing for lactose intolerance is the elimination diet. This involves removing foods from your diet which contain lactose and seeing if symptoms improve. If you then reintroduce lactose into your diet and symptoms reoccur, this may indicate you are intolerant or sensitive.

If you are lactose intolerant, it is important to seek advice on how to manage your diet. Dairy products contain important nutrients, especially calcium, and cutting them out of your diet completely may cause other issues. Some dairy products contain low levels of lactose that you may be able to tolerate.

Checking food labels can help if you are trying to avoid lactose. Some ingredients to look out for include milk solids, whey and milk sugars.