Lactose and whey are two chemically unrelated components of cow's milk and other animal milks. While many individuals can process both lactose and whey without difficulty, there are those who are sensitive to one or both, which results in either lactose intolerance or a milk allergy. Knowing whether you're sensitive to lactose or whey can help you make decisions about which foods you can comfortably eat.
Lactose
Lactose is the chemical name for milk sugar. Despite the fact that it's technically a sugar and is closely related to table sugar from a chemical perspective, lactose doesn't taste particularly sweet. It's made up of two units called monosaccharides. Specifically, lactose consists of the monosaccharides glucose and galactose. Your intestine can absorb glucose and galactose, but it can't absorb lactose. As such, when you consume dairy, you use the enzyme lactase to break lactose into glucose and galactose, say Drs. Reginald Garrett and Charles Grisham in their book "Biochemistry."
Whey
Unlike lactose, whey is a protein. It's quite chemically different than lactose and is made up of units called amino acids rather than monosaccharides. To absorb the nutrient components of whey, enzymes called proteases in your stomach and intestine break whey into its constituent amino acids, and your intestine absorbs the amino acids into your bloodstream. There are many proteins in milk, of which whey is only one example. Other major proteins in milk include casein and lactalbumin.
Intolerance and Allergy
If you can't eat dairy without discomfort, it's possible that you are lactose intolerant or allergic to whey. Lactose intolerance occurs when you don't produce the lactase enzyme, meaning you can't digest lactose. If you're lactose intolerant, consuming dairy causes digestive symptoms including gas and cramping. Whey allergy occurs when your immune system responds to the whey protein. You can get digestive symptoms with whey allergy, but it's also possible to have a much more serious reaction. MayoClinic.com says that allergic reactions to dairy can include hives, itching and difficulty breathing.
Safe Foods
If you're intolerant of lactose, it's safe to consume lactose-free dairy, because you're not allergic to any component of the milk. There are lactose-free milks, cheeses and other dairy products. Furthermore, most yogurt is naturally lactose-free, because the bacteria have "pre-digested" the lactose. If you're allergic to whey, however, you will have to avoid all dairy. This is because it's not possible to remove whey from milk, and any dairy carries with it the potential to cause a serious allergic reaction.
References
- "Biochemistry"; Reginald Garrett, Ph.D. and Charles Grisham, Ph.D.; 2007
- MayoClinic.com: Milk Allergy
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