Lactose Intolerance - A Quick Guide

By Les Willis, Nutrition Consultant

What is lactose?
Lactose is a type of sugar found in milk; it is two simple sugars called galactose and glucose joined together. Your body produces an enzyme in the small intestine that splits lactose into these two parts so they can be absorbed, this enzyme is called lactase.

What is lactose intolerance?
Having lactose intolerance, also known as alactasia, means that there is not enough of the enzyme lactase to turn all the lactose you have just consumed into glucose and galactose. As a result undigested lactose passes through to the colon. The colon is only supposed to get the parts of our food and drink that cannot be digested, when the lactose arrives it ferments. It is the fermentation of lactose in the colon that gives the characteristic symptoms of lactose intolerance.

What are the symptoms of lactose intolerance?

  • Diarrhoea
  • Abdominal bloating
  • Gas
  • Wind
  • Stomach cramps
  • Some people may experience vomiting (more common in children)

Do I have to eliminate milk and dairy completely?
Not usually; with any intolerance each individual has an amount they can consume without experiencing any effects. It is once they go above this level that they get the problems. Also, lactose is not in all dairy products, so it's only necessary to limit those with lactose in them. And it is now possible to buy products which have had the lactose removed meaning a low lactose diet or even a lactose-free diet does not have to be that limiting at all.

How do I know if a food is high in lactose?
Use the table below as a guide. However, look carefully for non-milk fat solids or skimmed milk powder as an ingredient. This can contain up to 52% lactose and finds its way into all sorts of commercially produced foods from cottage cheese, yogurt and low fat ice cream, to ready grated cheese, batter mixes and even some bread. The addition of skimmed milk powder to a product can turn a food that you would expect to have no lactose or be suitable for a low lactose / lactose free diet into one to avoid at all costs.

Also check for the following ingredients: lactose (often used in medicines), milk, milk powder, milk solids, non-fat milk solids, cream, margarine, whey, whey solids, whey powder, whey syrup and sweetener.

Whey protein and lactose
Whey protein sold for commercial use is much higher in fat and lactose (often 35% protein) than the product sold as a nutritional supplement (usually 75% protein or more). It is always best to check, but often whey protein concentrate 75% (and above) and whey protein isolate 80% (and above) are well tolerated by those who have problems with lactose intolerance.

How common is lactose intolerance?
It is estimated that over half the world's adult population have some degree of lactose intolerance, which really says that those who have no lactose intolerance are the odd ones out. Some populations are more at risk than others: if you are Swedish you have pretty much the lowest risk of becoming lactose intolerant, followed by European settlers in Australia. Caucasians in general have a risk of less than 15%, although Finns have an 18% chance of being lactose intolerant.

If you are African then the risk of being lactose intolerant rises; for African Americans it is up to 75%. For the Chinese the risk is 93% and for Thais it is 98%; however, Native American Indians could have a 100% risk.

Are there different types of lactose intolerance?
Yes there are:

Congenital: there are two types of inherited lactose intolerance. Either there is not enough lactase enzyme produced, or there is plenty of lactase enzyme produced but it doesn't work because it is faulty.

Premature babies can get what is called Development Lactase Deficiency. Simply put, their intestines have not developed enough to be producing the enzyme. As the baby develops they should start producing the enzyme and gradually grow out of their intolerance.

Adults get different types of lactose intolerance too. Late Onset Lactase Deficiency is the most common. Lactase enzyme levels are at their highest as a baby – when your diet is all milk – and then decline over the years. As you get older the fall in the amount of lactase enzyme produced can lead to intolerance. This type is also known as Primary Lactose Intolerance or Primary Lactase Deficiency. The other type is known as Secondary Lactose Intolerance or Secondary Lactase Deficiency.

This type of intolerance is caused by the part of the intestine that makes lactase becoming damaged. Common causes are food poisoning, long courses of antibiotics, inflammatory bowel disease, Crohns disease, coeliac disease and diabetes.

In Secondary Lactose Intolerance the small finger like projections which cover the intestine wall called villi, (the term brush border describes the villi very well) become damaged. The enzyme lactase is made by cells at the very tips of the villi. This area is vulnerable to damage and if enough villi are damaged then you no longer have enough lactase enzyme. If this happens you have lactose intolerance; however, when the villi repair themselves the intolerance should go away.

Meal Plan for Lactose Intolerance