Lactose monohydrate is a dairy product often used in packaged foods and other products for flavor and filler. In most people, lactose monohydrate causes no side effects. However, if you are lactose intolerant, it may cause some adverse reactions.
First, here's some milk 101: Lactose is the main carbohydrate found in milk, per a 2021 report in the Journal of Dairy Science. It is a key component in several dry dairy products and has a large effect on the physical characteristics of milk powders and other dried dairy ingredients.
There are two forms of lactose: alpha-lactose and beta-lactose. The solid form of lactose monohydrate forms when alpha-lactose is crystallized at low temperatures and dried. Lactose monohydrate is made from cow's milk and is the most common solid lactose in commercial milk powders as it doesn't easily take up or retain water. In other words, it can be stored without absorbing moisture from the air, per the report.
This crystalline form of milk powder looks like a white or pale yellow powder and smells just like milk, according to a March 2015 report from Transparency Market Research. Lactose monohydrate has been generally recognized as safe (GRAS) by the FDA for use as an additive in edible products in controlled quantities.
Where Is Lactose Monohydrate Found?
Lactose monohydrate appears in a wide range of foods, beverages, cosmetics, pharmaceuticals and even animal feed, per the Transparency Market Research report. It has a bland taste and is often used as a stabilizer — and it has the perk of being less expensive but having a longer shelf life than real milk.
You'll find lactose monohydrate in:
- tablet capsules
- infant formula
- ready-to-make foods
- ice cream
- bread and other bakery products
It's also used as a filler in medicines and animal feed for its physical and chemical stability.
In general, lactose in some form is used in more than 20 percent of prescription drugs and 65 percent of over-the-counter medications, per a May 2018 article in the International Journal of Polymer Science.
Lactose monohydrate may be listed as an ingredient on packaged food, according to the Institute for Quality and Efficiency in Health. It's typically not used for home cooking, though you may come across lactose monohydrate available commercially and marketed as a natural sweetener.
Side Effects of Lactose Monohydrate
It's important to know when lactose monohydrate is used in packaged goods or other foods you might eat if you have lactose intolerance or otherwise experience symptoms from dairy products.
People with lactose intolerance can't fully digest the sugar (lactose) in milk, which can lead to diarrhea, gas and bloating after eating or drinking dairy, per the Mayo Clinic. Lactose intolerance typically occurs when your body doesn't make enough of the digestive enzyme lactase.
Here's what to know about potential lactose monohydrate side effects.
If you're lactose intolerant, you may experience bloating 30 minutes to two hours after consuming foods or drinks with lactose such as lactose monohydrate, per Johns Hopkins Medicine. The severity of the bloating will depend on how much you've taken in and how much lactase your body makes.
Bloating can be managed by limiting or, if needed, removing products that contain lactose monohydrate from your diet. However, you can typically manage lactose intolerance symptoms by eating products containing dairy with other foods (like crackers or cereal), opting for products with naturally lower levels of lactose (think: hard cheeses or yogurt) or asking your doctor if you should take a lactase pill or droplets when you eat products containing lactose, per Johns Hopkins Medicine.
Although bloating is uncomfortable, keep in mind that lactose intolerance is not an allergy. When you have a food allergy like a milk allergy, your body has an abnormal response to a food triggered by your immune system and it can be life-threatening — so you must avoid those foods altogether, per the FDA.
If your body doesn't make enough lactase to digest lactose, you may experience gas in addition to other symptoms, per the FDA.
As with other symptoms like bloating or diarrhea, the best way to avoid gas from lactose monohydrate is to change your diet. Although people with lactose intolerance were once told to completely avoid dairy products, today experts recommend trying various dairy foods to determine which ones cause fewer symptoms, per Johns Hopkins Medicine.
If you react poorly to products with lactose monohydrate, you may still be able to tolerate dairy foods like yogurt. You can also find lactose-free and lactose-reduced milk products at several health food stores.
3. Loose Stools or Diarrhea
As with other symptoms, loose stools or diarrhea may occur after having milk products like lactose monohydrate if you have lactose intolerance, per Mount Sinai. Keep in mind that other intestinal issues such as irritable bowel syndrome may cause similar symptoms. Your doctor can determine if you have a lactose intolerance with tests such as a lactose-hydrogen breath test, a lactose tolerance test or a stool pH test.
Remember, even if you have a low lactase level, you may be able to tolerate some lactose. For instance, most people with low lactase level can have up to half a cup of milk at a time without symptoms.
If you do experience diarrhea as a symptom of lactose monohydrate, there are a few best practices for treating your symptoms. In general, an acute case of diarrhea is best treated by drinking ample water and electrolyte balanced fluids to prevent dehydration, per the Cleveland Clinic. Avoid foods and drinks with caffeine or lactose until your diarrhea has been resolved.
- Journal of Dairy Science: "Lactose: Use, measurement, and expression of results"
- Transparency Market Research: "Lactose Monohydrate Market - Global Industry Analysis, Size, Share, Growth, Trends And Forecast 2014 – 2020 : Transparency Market Research"
- Institute for Quality and Efficiency in Health: "Lactose intolerance: Shopping tips for lactose-intolerant people"
- Mayo Clinic: "Lactose intolerance"
- Johns Hopkins Medicine: "Lactose Intolerance"
- U.S. Food & Drug Administration: "Problems Digesting Dairy Products?"
- Mount Sinai: "Lactose intolerance"
- Cleveland Clinic: "Diarrhea"
- International Journal of Polymer Science: "Preparation and Characterization of High Purity Anhydrous β-Lactose from α-Lactose Monohydrate at Mild Temperature"