How many of these rumors about milk do you believe?

Author: Han Lu, Associate Researcher, Chinese Center for Disease Control and Prevention

Reviewer: Fu Rui, Chief Physician, Beijing Century Altar Hospital, Capital Medical University

In the hustle and bustle of life, there is a drink that always accompanies us, and that is milk. In the morning, a cup of warm milk awakens the dormant taste buds and injects full energy into the new day; in the afternoon, when fatigue strikes, a cup of iced milk coffee or milk tea can not only refresh the mind, but also bring a moment of tranquility and enjoyment; at night, a cup of steaming hot milk can help us relax and relieve the fatigue of the day. It is this gift from nature that has captured the hearts of countless people, and rumors about it have never stopped.

Figure 1 Copyright image, no permission to reprint

1. Is it true that drinking too much milk can cause cancer?

Some people believe that certain components in milk, such as casein, may promote the occurrence of cancer. However, this statement has not been fully scientifically confirmed. Scientific research is an important basis for judging whether a view is correct. After long-term research and observation, many authoritative medical research institutions and scientists have not found evidence that milk directly causes cancer. Globally, residents of many countries regard milk as an important part of their daily diet. If milk is really carcinogenic, then the incidence of cancer in these countries should be abnormally high, but this is not the case. Moreover, drinking milk in moderation has positive significance for maintaining good health and reducing the risk of certain chronic diseases.

2. Is it true that heating milk in a bag will produce harmful substances?

Plastic bags are the most commonly used packaging form for pasteurized milk (referred to as "pasteurized milk"), which is both economical and environmentally friendly. For convenience, many people often soak pasteurized milk directly in hot water, boil it in water, or even heat it directly in a microwave oven. Although these heating methods are simple, they do produce harmful substances in some cases. The plastic bags used for pasteurized milk are mostly made of low-density polyethylene, which is a very common food packaging bag material. It is relatively safe at room temperature and will not affect the quality of milk, let alone produce harmful substances. However, in a high temperature environment (115°C and above), low-density polyethylene will decompose, and the properties of the plastic bag will also change, which will affect human health. Therefore, it is not dangerous to soak or boil the pasteurized milk in hot water, because the boiling point of water under standard atmospheric pressure is 100°C, and low-density polyethylene is relatively stable in this environment. However, since the highest heating temperature of microwave ovens on the market often exceeds 115°C, it is not advisable to heat the milk in a microwave oven. It is still necessary to pour the milk into a container dedicated to the microwave oven and then use the microwave oven to heat it.

3. Drinking milk in the morning is easier to absorb, and drinking milk before bed can help you sleep. Is this true?

In fact, there is no clear time limit for drinking milk. You can drink it at any time and the nutritional effect is the same. After milk enters the human body and is metabolized, the nutrients will be absorbed in the form of molecules. As for how much can be absorbed, it does not depend on our subjective will, but more on the food itself and the storage of various nutrients in the human body. The human body will appropriately adjust its absorption rate according to the storage situation of a certain nutrient. For example, when the human body lacks iron, the body will increase the absorption rate of iron in food, and this change is not related to the time of meal.

Although milk contains tryptophan, which is considered to be the raw material for synthesizing melatonin and 5-hydroxytryptamine, and helps people reduce anxiety and promote sleep, the tryptophan content in milk is not high, only about 30 mg in 100g, which is 1/2 of the same weight of eggs and 1/6 of millet. Moreover, the amount of milk we drink each time is usually not much, about 200-300ml, and the sleep-inducing effect is very limited.

Figure 2 Copyright image, no permission to reprint

4. Is it true that the more expensive the milk, the better it is?

First, the price of a commodity often depends on many factors. Take milk as an example. Its price is affected by factors such as raw material cost, processing and transportation cost, packaging material cost and marketing added value, and raw materials only account for a small part of it. Milk with a long shelf life will be more expensive in the market, not because of its higher nutritional value, but because this type of milk uses more expensive Tetra Pak packaging to extend its shelf life, while pasteurized milk is slightly cheaper because its packaging material is relatively cheap.

Secondly, from the perspective of nutritional content, there is actually not much difference between different brands of milk. On the one hand, different milk sources do affect the nutritional quality of milk. According to the relevant national standards for dairy products, as long as the protein content in every 100ml of milk reaches 2.8g, it is qualified. Of course, the higher the protein content, the more expensive the milk may be. On the other hand, different production processes also have a slight impact on the nutritional quality of milk. Generally speaking, pasteurized milk loses less nutrients.

Furthermore, some people say that expensive milk tastes better and thicker, but this is not true. The taste is mainly related to the fat content of milk. The higher the fat content, the more fragrant and thicker it tastes. Skim milk tastes as light as water, but its price is more expensive than whole milk.

Therefore, when choosing milk, don't just focus on the brand and price. The protein and calcium content in the nutritional table is also very important. In addition, personal taste, habits and physical fitness are also very important reference factors. For some special groups, such as those with lactose intolerance, you can choose low-lactose or lactose-free milk products, or supplement nutrients such as calcium and protein through other means. I would like to remind everyone that when drinking milk, you also need to pay attention to the principle of moderation. Excessive intake of any food may cause harm to the body.

In short, when facing various rumors, we should maintain a rational and scientific attitude and not be easily misled by statements without scientific basis. Milk is an indispensable source of nutrition in life, and it is worthwhile for us to continue to include it in a healthy diet.