Yes, pure milk will be less nutritious when it is boiled.
Milk boiling, the protein contained in the state of soluble into a gel state, where the calcium will appear phosphate precipitation phenomenon, vitamins are destroyed, while the milk lactose in the high temperature will be caramelized, affecting the human body to absorb. It is best to use the "pasteurization method", that is, fresh milk heated to 62 ℃ for 30 minutes, or heated to 71 ℃ for 20 minutes, so that both the bacteria can be killed, but will not affect the absorption.
Drinking cold milk is not recommended, it can cause stomach upset, and it is recommended to heat it up a little bit before drinking it. Microwave heating is more convenient, but need to pay attention to the plastic bag can not be directly heated, to use the glass container heating. As for the milk with or without sugar, and digestion has little to do, mainly to improve the taste.
Expanded Information:
Drinking milk:
Drinking milk in moderation every day will not make you fat, but you can't take milk as water, adults drink about 300ml a day, but the total intake of dairy products can't be more than 500ml. it is important to note that drinking milk on an empty stomach will lead to the protein and other components of which, not fully digested into the intestine. that cause nutrient loss.
Milk, bread with fruits and vegetables or eggs, cereal porridge with fruits and vegetables, are better with breakfast, so that the milk and saliva digestive enzymes in full contact with the more favorable composition absorption. For people with a bad stomach, you can drink honey milk about an hour before the meal. Take a break after meals to drink milk, the stomach has starchy food, can help the milk in the protein to be fully absorbed.
People's Daily News - Drinking milk is a "technical job"
Baidu Encyclopedia - Milk
People's Daily News - Does milk need to be boiled? What are the contraindications and misunderstandings of drinking milk