Infant mammals nurse on their mothers to drink milk, which is rich in<unk> . The intestinal villi secrete the enzyme<unk>  (β-D-galactosidase) to digest it. This enzyme cleaves the<unk>  molecule into its two subunits, the simple sugars glucose and galactose, which can be absorbed. Since<unk>  occurs mostly in milk, in most mammals, the production of<unk>  gradually decreases with maturity due to a<unk> k of continuing consumption. Many people with ancestry in Europe, West Asia, South Asia, the Sahel belt in West Africa, East Africa and a few other parts of Central Africa maintain<unk>  production into adulthood. In many of these areas, milk from mammals such as cattle, goats, and sheep is used as a large source of food. Hence, it was in these regions that genes for lifelong<unk>  production first evolved. The genes of adult<unk>  tolerance have evolved independently in various ethnic groups. By descent, more than 70% of western Europeans can digest<unk>  as adults, compared with less than 30% of people from areas of Africa, eastern and south-eastern Asia and Oceania. In people who are<unk>  intolerant,<unk>  is not broken down and provides food for gas-producing gut flora, which can lead to diarrhea, bloating, flatulence, and other gastrointestinal symptoms.
Lactose
Methyl cellulose
Ribose
Chitosan
Corn starch
Icodextrin
Acemannan
Thiamylal