Some people consider it unethical to drink milk such as vegans and some people only drink milk from cows who were milked in a less cruel way than the way some cows are milked. As far as milk goes in and of itself though much milk in America and possibly elsewhere is fortified with vitamin d.
Vitamin d fortified milk has caused kidney disease in many kids. I recently talked with someone who will remain unnamed who developed kidney disease when they were very young(about 6 years old). This happened because when they were a kid they loved to drink lots of milk and due to the milk being fortified with vitamin d this persons kidney became diseased because the amount of vitamin d consumed was too much for a young persons body to handle. As a result of too much vitamin d this person developed kidney disease.
This is simply another example of why it is best for people not to meddle in the food that is being produced. Whether it is vitamin d in milk or fluoride in the water there is always something that goes wrong as a result of consuming food that has been altered in some way.
There are also reports of people developing all sorts of health problems after taking vitamin d supplements.
Vitamin d is healthy for people but it is not good to take vitamin d supplements or eat foods fortified with vitamin d. People naturally get vitamin d from the sun. Getting too much sun is bad but sunbathing for moderate amounts of time is healthy. Sunscreen however is poisonous.