Chalav Yisroel, very loosely translated as “Jewish milk” is a stringency in the laws of kashrut (kosher) that stipulates that all milk and dairy products should be manufactured under Jewish supervision. This means that either the cows should be milked by Jews or the milking and the production of cheeses, ice creams and other dairy foods should be done with a Jew in attendance.
A common misconception about chalav Yisroel is that any dairy food with a kosher label is automatically chalav Israel. Milk and cheese with the OU-D symbol, for instance, are kosher products (coming from kosher animals with a kosher certificate), but are not chalav Yisroel. If a dairy product is chalav Yisroel, it should either indicate this on the label, or clearly be produced by a Jewish company, such as HaOlam cheese.
Another misconception about chalav Yisroel is that it is just a custom. The Shulchan Aruch, or the code of Jewish law, discusses chalav Yisroel as a requirement for keeping kosher and not just an added stringency. Many people cite Moshe Feinstein’s ruling that regular OU-D milk or cheese will suffice if Chalav Yisroel is not available as a reason for not buying chalav Yisroel products. However, Rabbi Feinstein was referring to cases where chalav Yisroel products were absolutely not available and in cases where milk was necessary, as is the case with young children.
It is thought that chalav Yisroel helps strengthen one’s connection to Hashem, according to Chassidic writings. There is a story about a rabbi who arrived in a Jewish village in Europe and noticed that the people were very observant, but did not believe that the messiah would come. On closer examination, he realized that the people were scrupulous about every mitzvah except when it came to eating chalav Yisroel. This caused them to doubt the concept of messiah, which is a central belief according to the Rambam.