An Introduction to Lactose Intolerance
If you have ever felt a period of discomfort, bloating, or cramping after a milky coffee or a bowl of ice cream, you are not alone. Lactose intolerance is the most common food intolerance across the world. While not everyone develops a true intolerance, most people lose some ability to digest lactose as they become an adult, which is why even for those who aren't intolerant, overindulging in milk or cheese can still still leave us needing the bathroom!
Ongoing digestive symptoms can be frustrating and confusing, but the good news is that with a little knowledge, lactose intolerance is a very manageable condition. This article is your starting point. We will walk you through what lactose intolerance is, what causes it, and how you can begin to navigate your relationship with dairy to feel your best.
What Is Lactose and the Lactase Enzyme?
To understand lactose intolerance, we first need to look at two key players: lactose and lactase.
Lactose is the natural sugar found in milk and dairy products. It is a type of sugar called a disaccharide, which means it is made of two smaller sugar units bonded together: glucose and galactose. For your body to absorb and use these sugars for energy, they first need to be separated.
This is where lactase comes in. Lactase is an enzyme produced in the lining of your small intestine. Its one specific job is to break down lactose into glucose and galactose. Think of lactase as a pair of scissors, perfectly designed to snip the bond holding the two sugar molecules together. Once separated, your body can easily absorb them into the bloodstream.
Lactose intolerance occurs when your body does not produce enough of the lactase enzyme. Without sufficient lactase, the lactose you consume cannot be broken down and absorbed in the small intestine. Remember that 'sufficient lactase' is relative to the amount of lactose that you have consumed. You don't need a lactose intolerance to experience these reactions - if you've overindulged in a cheese platter you can still experience discomfort later that day!
What Happens to Undigested Lactose?
If you don't produce enough lactase, then the lactose you've ingested will continue its journey from your small intestine into the large intestine (the colon), which is not somewhere that it's meant to go. There, it meets the trillions of bacteria that make up your gut microbiome.
For these bacteria, undigested lactose is a feast. They begin to ferment the sugar, a process that produces gases like hydrogen, carbon dioxide, and methane. This fermentation process is the root cause of the most common reactions associated with lactose build up, which include:
- Bloating and Gas: The excess gas produced by the bacteria builds up in the large intestine
- Abdominal Pain and Cramping: The stretching of the intestinal wall from gas and water can cause discomfort and pain
- Diarrhoea or Loose Stools: Undigested lactose draws water into the colon, which can lead to watery stools
Experiencing these reactions doesn't mean that you necessarily have a lactose intolerance. Also, the timing and severity of these reactions can vary from person to person, often appearing anywhere from 30 minutes to a few hours after consuming dairy.
Lactose Intolerance or Histamine Intolerance?
At this point we want to highlight that there is an overlap in both reactions and triggers between lactose intolerance and histamine intolerance.
Histamine is a chemical that builds up in food in a number of ways, but most commonly as it ages or ferments. Hard, blue or processed cheeses are all aged or fermented, as are dairy products like kefir, and are all high in histamine.
We have an article that looks specifically at this overlap between lactose and histamine intolerance, and goes into detail on ways that you can understand the difference. As ever, keeping a food diary is key to helping understand what is going on.
A Crucial Distinction: Intolerance vs. Allergy
It is incredibly important to distinguish between lactose intolerance and a milk or dairy allergy, as they are two completely different conditions with different mechanisms and potential consequences.
- Lactose intolerance is a digestive issue. It is caused by an enzyme deficiency (not enough lactase). While uncomfortable, it is mostly confined to the gastrointestinal tract and are is life-threatening
- A milk allergy is an immune system response. The body’s immune system mistakenly identifies proteins in milk (like casein or whey) as harmful invaders. It releases chemicals to fight them off, which can cause reactions that is severe cases, can lead to life-threatening anaphylaxis
A healthcare practitioner can help you understand what you might have, and help create strategies to manage to manage it. This may include limiting lactose intake, or supporting your body with enzyme supplements if appropriate.
The Different Types of Lactose Intolerance
Not all lactose intolerance is the same. It is generally categorised into three main types:
- Primary Lactose Intolerance: This is the most common type. It is a genetically determined condition where lactase production gradually declines after infancy. This decrease is a normal process for many people globally, with prevalence varying significantly across different ethnic backgrounds
- Secondary Lactose Intolerance: This type occurs when an injury or illness damages the lining of the small intestine, where lactase is produced. Potential causes include a gut infection (like gastroenteritis), coeliac disease, or Crohn's disease. In many cases, if the underlying condition is treated, lactase production may return to normal
- Congenital or Developmental Lactose Intolerance: This is an extremely rare genetic disorder where a baby is born with little or no lactase production from birth
Finding Your Personal Threshold
One of the most empowering things to understand about lactose intolerance is that it is rarely an all-or-nothing condition. Most people with lactose intolerance do not always have to eliminate dairy completely. Instead, they have an individual threshold, which is the amount of lactose they can consume without experiencing significant symptoms.
This threshold is unique to you. Some people might be able to tolerate a splash of milk in their tea, while others might manage a small bowl of yoghurt. Consuming lactose-containing foods as part of a larger meal, rather than on their own, can also slow down digestion and improve tolerance for many people.
Learning your personal limit is a process of careful observation. Keeping a food and symptom diary can be an incredibly useful tool on this journey.
Are Some Dairy Products Easier to Digest?
Yes. The way dairy products are processed can significantly affect their lactose content. Many people with lactose intolerance find they can comfortably enjoy certain types of dairy, including:
- Hard, Aged Cheeses: Cheeses like cheddar, Parmesan, and Swiss are naturally very low in lactose. During the cheesemaking and ageing process, most of the lactose is drained off with the whey, and the remaining amount is broken down by bacteria
- Yoghurt with Live Cultures: The live, active bacteria (probiotics) in yoghurt help to break down some of the lactose, essentially doing part of the lactase enzyme’s job for you
- Butter: Butter is mostly fat and contains only trace amounts of lactose, making it well-tolerated by most
How Is Lactose Intolerance Diagnosed?
If you suspect you have lactose intolerance, the first step is always to speak with a qualified healthcare professional to rule out other conditions. They may recommend a formal test or an elimination diet, depending on your own personal circumstances.
At Tolerance, we offer at-home genetic testing, that can help you understand whether you have a genetic predisposition towards lactose intolerance. Our Core Genetic Report looks at 27 different genes including those responsible for lactose, gluten and caffeine breakdown, which are the three most common intolerances globally.
Living Comfortably with Lactose Intolerance
Receiving a diagnosis of lactose intolerance can feel restrictive at first, but we encourage you to see it as an opportunity to understand your body better. Management is not about deprivation, it is about finding a new balance that works for you.
A registered dietitian can be an invaluable partner in this process. They can help you identify your personal threshold, find suitable dairy and non-dairy alternatives, and ensure you are still getting enough essential nutrients like calcium and vitamin D, which are vital for bone health.
Ultimately, managing lactose intolerance is about listening to your body and making informed choices. With a bit of knowledge and planning, you can continue to enjoy a varied and delicious diet without the discomfort.
This article is for informational purposes only and does not constitute medical advice. Please consult a qualified healthcare professional for advice specific to your situation.