Lactose intolerance

1) Hi Alice,

For some years I did not drink milk, but started to take a lot of milk just recently and discovered I cannot digest milk without developing a lot of gas, stomach aches, etc. I did not have that problem before I stopped drinking milk. Will I develop more lactase, i.e., the ability to digest milk, as time goes on and I drink more milk, or will I have to take Lactaid milk for the rest of my life (it's not available in some countries).

2) Dear Alice,

What are the symptoms of lactose intolerance (i.e., how long after taking a milk product will symptoms generally begin, and what are the typical symptoms), and how do they differ from irritable bowel syndrome?

Dear Readers 1 and 2,

Got lactose-free milk? Lactose intolerance is a very common condition in which lactose, a sugar found in milk and dairy products, can’t be completely digested. This can occur when a person has a lactase deficiency, which is an enzyme produced by the small intestine that breaks down lactose for digestion. If there is any lactose that remains undigested, it moves into the colon where bacteria break it down. This could lead to some common symptoms of lactose intolerance, which usually occur within 30 minutes to 2 hours after ingesting a lactose-containing product. These symptoms could include:

  • Abdominal pain
  • Bloating
  • Gas
  • Nausea
  • Cramps

When it comes to causes, there are three kinds of lactase deficiency that could lead to lactose intolerance:

  • Primary lactase deficiency is the most common type. Folks with this type start off life producing plenty of lactase but it decreases over time. They may not experience symptoms of lactose intolerance until early adulthood.
  • Secondary lactase deficiency occurs when the small intestine isn’t able to produce enough lactase after an injury, illness, or infection. This lactose intolerance could be improved if the underlying ailment is treated.
  • Congenital lactase deficiency is a very rare type that happens when an individual is born with an inherited gene that causes the small intestine to produce very little or no lactase at all.

Generally speaking, people produce less lactose as they age — that is, people become less and less able to break down lactose as they grow older. So, Reader 1, this may explain why you’re now experiencing these symptoms. But don’t worry, you’re not alone! Many cases of lactose intolerance in adults first develop in between the ages of 20 and 40.

Reader 2, you asked about the similarities between lactose intolerance and irritable bowel syndrome (IBS). While lactose intolerance may share some common symptoms with IBS, they’re two different conditions that affect different organs in the body and are caused by different factors. IBS is a disorder that adversely affects the large intestine and can be caused by a number of factors such as stress, changes in microbes in digestive system, infection from bacteria or virus, or abnormalities in nervous system.

So, how do you know if you’re lactose intolerant? It might help to chat with a health care provider. If your stomach is revolting every time you eat dairy products, your provider may suspect lactose intolerance and conduct a lactose tolerance test or a hydrogen breath test to confirm their suspicions.

Unfortunately, when it comes treatments for lactose intolerance, there’s no known cure or way to prevent it. But fear not! There are several strategies to help manage your lactose intolerance including:

  • Lactase enzymes, which can be taken as a tablet or drop, may help reduce the chances of developing digestive symptoms. It's recommended that you check with a health care provider before using these products because some folks (such as young children and pregnant and breastfeeding women) may not be able to use them. Also, keep in mind that not everyone finds these products helpful and even without the help of lactase enzyme supplements, most lactose intolerant people can handle some lactose in their diet without any symptoms.
  • Consuming smaller servings of dairy, especially at mealtimes when food slows down digestion.
  • Trying out different types of dairy products because not all contain the same amount of lactose (for example, certain hard cheeses and yogurt may cause fewer symptoms).
  • Giving lactose-reduced or lactose-free products a try. These products pretty much resemble regular milk products, but with the addition of lactase, and can be found in a majority of grocery stores.
  • Taste-testing different non-dairy cheeses, milks, and yogurts made from different sources (such as soy, rice, almonds, coconuts, etc.).

Of course, the only way to avoid lactose intolerance symptoms completely is to not eat any foods containing lactose. This can be tricky as some non-dairy foods, such as breads, cereals, snacks, salad dressings, and cake mixes, also contain lactose. Reading food labels can help you check for lactose-containing ingredients, such as milk, milk solids, whey (milk liquid), and casein (milk protein). Additionally, some prescription and over-the-counter drugs, as well as nutritional supplements may contain lactose. If you’re unsure whether your new or existing medications or supplements contain lactose, you may talk with your health care provider or your pharmacist to get more information.

Finally, if you're experiencing lactose intolerance, it may be key to pay attention to what you eat so you're still meeting your daily calcium and vitamin D needs. You could also try speaking with a registered dietitian to get more information about your nutrition needs. If you'd like even more information on lactose intolerance, you could consider checking out the National Institute of Diabetes and Digestive and Kidney Diseases.

Hope this helps!

Last updated Nov 27, 2020
Originally published Oct 30, 1998

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