I drink 1.5 to 2 liters of milk a day. Is it healthy?
There are several risks related to excessive consumption of milk. A 12 years prospective study run on around 78000 women showed that high consumption of milk (2-3 glasses per day) increased the risk of fracture when compared to people who used to drink one glass or less per week. (1) Similar results were found in other studies like, for example: 2.
The amount that you say, 1.5 L, contains about 1800 mg of calcium, that must be sum to other daily dietary sources (as dairy, green leaves, sesam seeds, water). A study showed that dietary intakes of calcium greater than 1400 were associated with higher death rates from all causes, cardiovascular disease and ischaemic heart disease (3).
Consuming anything in excessive amounts for a long period of time is not good for your health. There are two main problems. One is that the stomach will get upset and other is that you can have allergies. The other problems depend on the elements that the food or drink contain most. Generally high amounts of milk are taken for protein and calcium. Such amounts are generally taken by body builders and athletes, but not for a long time. They start to take it several months before their competition, usually three or four months. Sometimes, for people with some medical conditions, consumption of high amounts of milk is suggested but not as high as 1.5 or 2 liters.
Before I answer your question some important things need to know are why you are drinking such a high amount of milk, how long will you be doing this, have you done this before, and what kind of the milk will it be (ie: cow, goat, soybean etc.). I am assuming that you want to drink cow's milk. The best way to get answer this question is google just type "side effect of take excessive amount of milk". you will get many result. Here I have given some link generally i use these links...