It is estimated that 1 in 20 Caucasians experience some lactose intolerance and the rate is even higher amongst those of non-Northern European descent, affecting up to 90% of people in East Asian countries.
Lactose intolerance is caused by an inadequate quantity of the lactase enzyme, which breaks down the lactose in dairy to glucose. Whilst almost everyone has the ability to produce lactase to digest breast-milk, in those cultures without a long history of consuming unfermented dairy products, people are less likely to inherit the changes in gene expression which allow lactase to be produced later into life.
An intolerance is different to an allergy and common symptoms include gastrointestinal upset, such as bloating, cramps, flatulence and diarrhoea.
Diagnosis of lactose intolerance can be performed with hydrogen breath testing, methane testing, lactose tolerance blood testing, duodenal biopsy, elimination diets, or a milk challenge. Whilst hydrogen breath testing is considered the gold standard for diagnosis, some people produce lower amounts of hydrogen which may go undetected, and 15% of people actually produce none, which may result in false-negatives. Methane testing can be used in such cases if an intolerance is still suspected, however 5% of people produce neither hydrogen nor methane.
Whilst a common treatment for lactose intolerance is the avoidance of dairy foods, this means cutting out a nutritious and enjoyable food group and an increased risk of low bone mineral density. Some lactose intolerant people may actually be able to tolerate small amounts of lactose and hence do not need to avoid them completely, as they may still produce small amounts of lactase. Lactose free varieties of dairy products, like milk and cheese, can be substantially more expensive and may not be necessary.
Some good tips for including dairy foods are:
- Try smaller amounts of milk, such as 1/2 cup at a time and up to 2 cups spread out over the day (12g lactose).
- Choose full cream milk as this is usually better tolerated than skim-milk.
- Yoghurts are generally low in lactose as the bacteria ferments the lactose into lactic acid.
- Hard cheeses are generally naturally low in lactose.
- Combining small amounts of dairy foods in a meal may be better tolerated.
- Try lactose free milk varieties, or add lactase drops to regular milk.
If dairy foods are being avoided, it is important to replace them with other sources of vitamin B12, vitamin A, protein and particularly calcium.
Most adults require 1000-1300mg of calcium per day. Some good alternative sources of calcium include:
- Tinned fish with bones (~400mg absorbed per 1/2 cup)
- Almonds, brazil nuts (~40mg absorbed per 15 almonds)
- Calcium fortified products: cereal, bread, juice, non-dairy milks (check the label for calcium content)
- Broccoli (~20mg absorbed per 1/2 cup)
- Kale (~30mg absorbed per 1/2 cup)
- Bok choy (~40mg per 1/2 cup)
- Tofu (~80mg per 125g, but be sure it’s a calcium sulphate set variety!)
Have you heard that other leafy greens like spinach are a good source of calcium? Well, spinach contains about 100mg per cup cooked, however due to the presence of oxalates, as little as 5% may be absorbed. Bioavailability, the degree to which the calcium is absorbed, varies for different foods based on a number of factors, so be aware that often much less calcium is absorbed than the amount present. When choosing a fortified soy milk, most varieties will have 20-25% calcium absorption, so keep this in mind when reading the label.
Another tricky thing to beware of is lactose as an additive in packaged foods and medications. To avoid this, read processed food labels, such as cakes, soups and cheesy sauces for ingredients like milk solids, milk sugar or whey. Consult your pharmacist to determine whether there is any lactose in your medications.
This article is of a general nature and is not intended to replace personalised medical or dietetic advice. If you suspect you are lactose intolerant, please see your GP for diagnosis, or if you have been diagnosed with lactose intolerance please, consult an Accredited Practising Dietitian for individualised dietary advice.
Photo by Bambo