The Low FODMAP Diet: All About Disaccharides

If you follow the low FODMAP diet to manage your irritable bowel syndrome (IBS) symptoms, you may wonder what the letters stand for. Here, we will focus on the "D" in FODMAP. The "D" in FODMAP stands for disaccharides. The disaccharide of interest is lactose.

I will review why disaccharides affect IBS symptoms and which foods contain them. I will also provide some tips for eating the right amount of nutrients if you avoid lactose foods.

Disaccharides and digestion

Disaccharides are molecules made of 2 sugar units joined together. On the low FODMAP diet, lactose is the disaccharide to be concerned about. Lactose is made of glucose and galactose.¹

Since our body cannot digest lactose in its disaccharide form, it needs the lactase enzyme to split the molecule up for digestion. Once lactose is split into glucose and galactose, it is easily absorbed by the body.¹

People who do not make enough of the lactase enzyme have trouble digesting lactose. This is known as lactose intolerance. If a person has lactose intolerance, lactose travels to the large intestine undigested. There, it pulls water into the gut. The gut bacteria also feed on undigested lactose. This all leads to bothersome symptoms like gas, bloating, abdominal pain, and diarrhea.¹

What foods contain lactose?

Lactose is known as "milk sugar" because it is found in dairy products. Dairy products containing lots of lactose include milk, ice cream, and cream. Fermented dairy foods such as yogurt and kefir have moderate lactose. Aged cheeses like cheddar have virtually no lactose.¹

You do not need to cut out all dairy products following the low FODMAP diet. Since most cheese is quite low in lactose, it can be eaten even during the elimination phase of the low FODMAP diet.¹

Health benefits of lactose

While lactose does not have specific health benefits, foods that contain lactose do. Dairy foods are an excellent source of calcium, which is important for keeping our bones and teeth healthy and controlling muscle contractions. They are also a source of high-quality protein, which keeps your muscles strong.²

A review published in 2021 showed that milk consumption was associated with a lower risk of:³

• Heart disease
• Stroke
• High blood pressure
• Colorectal cancer
• Obesity
• Osteoporosis

If you are avoiding dairy due to lactose intolerance, it is important to make sure you get calcium from other sources. Here are a few non-dairy sources of calcium:⁴

• Canned fish, with bones
• White beans
• Tahini (sesame seed butter)
• Almonds
• Collard greens
• Kale
• Blackstrap molasses

Some people who enjoy dairy products and do not wish to give them up take lactase pills before eating dairy. These pills contain the lactase enzyme, which helps break down the lactose that the body cannot digest. Or you may wish to try lactose-free versions of common dairy foods like milk and yogurt.⁵

Final thoughts

The disaccharide lactose, found in many dairy products, can cause unpleasant symptoms such as gas, bloating, and diarrhea in people with lactose intolerance. If you are avoiding lactose-containing foods, getting calcium from other sources is important. Leafy greens and lactose-free dairy products are good sources of calcium.