Calcium, vitamin D and protein in dairy products are essential nutrients for human health. Therefore, people have long emphasized the benefits of dairy products to our health. But are dairy products harmful to health? In recent years, the incidence of cancer is getting higher and higher in both western countries and China.
So is there a relationship between dairy products and cancer? The relationship between dairy products and cancer risk has been controversial. For example, increasing dairy products and calcium intake can reduce the risk of colorectal cancer, but it will increase the risk of prostate cancer. Calcium and vitamin D in dairy products are related to reducing intestinal cancer. A large amount of saturated fat and calcium in dairy products is related to the increase of prostate cancer. Although the results of many previous studies are not uniform, this controversy has always existed.
Similarly, although the consumption of dairy products (mainly milk) in China has greatly increased, the average intake has increased from 1992 to 24.7g/ day in 20 12 years, but it is still far lower than that in western countries (for example, the intake in the United States in 20 15 years is about 400g/ day). So, is milk consumption related to cancer in China?
The first is the results of a prospective study on chronic diseases in China.
Recently, the prospective study of chronic diseases in China (CKB study) showed that the increase of dairy products intake was related to the increased risk of cancer, liver cancer, female breast cancer and lymphoma.
From 2004 to 2008, CKB research selected about 500,000 cancer-free residents from ten different areas (five cities and five rural areas) in China. During the average follow-up period of 10.8 years, nearly 10,000 cases of cancer occurred.
In the study, 20.4% residents regularly (1 day/week) eat dairy products (mainly milk), and the average intake of these residents is 80.8g/ day. The average intake of dairy products for all residents is 37.9g/day.
Cox regression analysis was performed on 5 10 and 146 participants who did not report cancer history at baseline. In the analysis, the following risk factors were considered, stratified according to risk age (continuous), gender (binary variable) and region (ten regions), and adjusted for education (four categories), income (four categories), smoking (four categories), drinking (four categories), overall intensity activity (continuous variable) and family history of cancer (binary variable).
The analysis of liver cancer also made additional adjustments to the HBsAg status (three categories). In the lowest (never/rarely), middle (monthly) and highest (regular) intake groups, the estimated crude average (g/day) of dairy products intake is 24.0, 44.4 and 80.8 g/day, respectively. The corrected P trend values of FDR related to the incidence of total cancer, liver cancer, lymphoma and female breast cancer were 0.002, 0.04, 0. 17 and 0.0 1 respectively.
There is a significant positive correlation between the consumption of dairy products and the risk of total cancer and cancer in some specific parts. After adjustment (after adjusting other lifestyles such as obesity), the risk of total cancer, liver cancer (n = 3 19 1), female breast cancer (n = 2582) and lymphoma (n = 9 15) increases every 50g/day, and the HR is/. 1.12 (1.02-1.22),1.19 (1.01-/kloc)
However, after adjusting many tests, the correlation with lymphoma was not statistically significant.
In addition, no significant correlation was observed between colorectal cancer (n = 3350,1.08 [1.00-1.17]) or other site-specific cancers. In other words, the higher the intake of dairy products, the higher the risk of cancer, liver cancer and female breast cancer. For every 50g/ day increase, the risk increases by 7%, 12%, 17% and 19% respectively. Other cancers have nothing to do with milk intake, including lung cancer, gastric cancer and pancreatic cancer.
According to the researchers, this is the first and largest prospective cohort study in China, which explored the relationship between dairy intake and cancer.
Second, the cause analysis of milk "carcinogenic"
Regarding the relationship between high intake of dairy products and cancer, the author speculates that there may be the following reasons:
Similarly, many international studies have reached similar conclusions.
The European Prospective Survey of Cancer and Nutrition (EPIC) recruited 520,000 people aged 20-85 in 23 centers in 65,438+00 European countries (Denmark, France, Germany, Greece, Italy, Norway, Spain, Sweden, the Netherlands and the United Kingdom) from 65,438 to 092-2000.
At present, the project has been going on for 15 years. The European Prospective Survey on Cancer and Nutrition conducted an average follow-up survey of 477,206 people 1 1 year, and analyzed the relationship between the total intake of dairy products, different intake of dairy products, nutritional components in dairy products (calcium, vitamin D, fat and protein) and the occurrence of liver cancer.
Eating a lot of dairy products and the difference between milk and cheese are all related to the increased risk of hepatocellular carcinoma. Calcium, vitamin D, fat and protein in dairy products are also related to the increased risk of hepatocellular carcinoma, while the same nutrients from non-dairy products can reduce the occurrence of hepatocellular carcinoma.
The daily intake of dairy products below 206.9 grams is low; The daily intake of 206.9 g -38 1.7 g dairy products belongs to the middle level; Eating more than 38 1.7 grams of dairy products every day is a high level. Compared with low-dose dairy products (less than 206.9g) daily, the risk of liver cancer is increased by 36% if dairy products with a medium level (206.9g-38 1.7g) are consumed daily, while the risk of liver cancer is increased by 66% if dairy products with more than 38 1.7g are consumed daily. Increasing the daily intake of dairy products 10% will increase the risk of liver cancer by 2%.
On the contrary, drinking yogurt less than 1 1 g every day is a low level; Drinking 1 1.0 g -67.2 g yogurt every day belongs to the medium level; Drinking more than 67.2 grams of yogurt every day is a high level. Compared with drinking a small amount of yogurt (1 1g or less) every day, drinking a moderate amount of yogurt (1.0-67.2g) every day reduces the risk of liver cancer 14%, while drinking a large amount of yogurt (above 67.2 g) every day reduces the risk of liver cancer.
Further research found that dairy products are related to the risk of liver cancer, and the levels of fat, vitamin D and calcium may also be related.
Third, the conclusion of China's research is perfect?
This large sample of 500,000 people in China, after long-term observation and research, has its important value, but it does not mean that a definite conclusion can be drawn. Although many factors related to cancer have been considered, Metz Medical believes that there are still many unknown factors that have not been considered:
1. After all, this is an observational study, not a randomized controlled trial, and it is still too early to draw a conclusion. In the future, it is better to further confirm with the help of tool variables.
2. This research began in 2004, which was the fastest period of economic development in China. During this period, people's lifestyles have changed rapidly, and these factors themselves will also have an impact on tumors. At the same time, this period is also the most serious period of environmental pollution in China. As we all know, environmental pollution has a great influence on the occurrence of cancer, and whether air purifiers are installed in every family will also affect the occurrence of tumors. These complex environmental factors have not been fully considered.
3. There are still many variables that have not been fully considered in this study, such as the type of milk, ordinary milk or high-fat milk, skim milk or yogurt? The possible conclusions are also quite different.
4. Cancer is an important disease, but milk will also have complex effects on cardiovascular diseases and diabetes, which should be considered comprehensively.
In a word, Metz Medicine believes that the quality of milk needs more comprehensive consideration.
Fourth, how to weigh the pros and cons of drinking milk? Also consider cardiovascular diseases and so on.
1, cancer is not only all, but also a considerable part of death caused by cardiovascular diseases.
Meta-analysis also shows that there is a significant nonlinear correlation between the total consumption of dairy products and the mortality of all-cause mortality and cardiovascular diseases. Studies have found that the intake of high-fat milk is significantly related to the risk of cancer death, cardiovascular disease and all-cause death. However, according to the overall data, the total consumption of dairy products is related to the low risk of death from cardiovascular diseases. This study believes that low-fat or skim milk may be more beneficial to health, while whole milk and high-fat milk, relatively speaking, have higher risks for some diseases.
2, different types of cancer, milk does not mean that all cancers are increased.
In fact, many studies have shown that milk intake is related to prostate cancer, breast cancer and liver cancer. However, a large number of systematic reviews also show that milk, especially fermented dairy products, especially yogurt and cheese, is negatively correlated with the risk of conventional and serrated colorectal cancer, that is, long-term intake of yogurt may reduce the risk of colorectal cancer.
5. Can children and teenagers drink milk?
In addition, at present, most studies focus on adults taking milk, so will teenagers taking milk increase the risk of cancer?
Meta's recent meta-analysis denies this. Studies have shown that milk intake in childhood and adolescence has nothing to do with breast cancer, colorectal cancer and prostate cancer in the future. Moreover, menopause, cancer stage, milk fat content and milk intake stage were also considered, and no correlation with tumor was found. The results of this study show that there is no correlation between milk intake of children and adolescents and future cancer.
Of course, milk is safer for babies. Don't worry about the safety of milk powder.
summary
Generally speaking, milk is still drinkable!
But it is suggested that yogurt and milk can be used together, and it may be more beneficial to use low-fat or skim milk. In addition, even yogurt should be sugar-free or low-sugar, otherwise it is not suitable for diabetics.
For future suggestions, we can observe what kind of people can benefit from milk through larger-scale clinical trials, so as to achieve accurate intake of milk. I believe that nutrition should also develop in the direction of "precise nutrition" in the future.
Tips: How much does the risk of illness/death increase?
The higher the intake of dairy products, the higher the risk of cancer, liver cancer and female breast cancer. For every 50g/ day increase, the risk increases by 7%, 12%, 17% and 19% respectively. So high, is it scary? It is necessary to understand what is increased risk and increased incidence.
For example, the mortality rate of a certain disease is 30%, and in some cases, the mortality rate will increase by 10%. At this time, the actual mortality rate in this case is 30%+30% *10% = 33%; So how much does the risk of death increase? It should be calculated like this. (Both cases are calculated by 100 people), the first case is 30/( 100-30), the second case is 33/( 100-33), and then the two are divided, which is [33/(/kloc-0). The actual situation is 100, and the number of deaths has increased by 3. How serious is this?
For another example, in 20 16 years, there were about 4.064 million new cancer cases in China, accounting for about1400 million people in China, that is, the overall cancer incidence rate (every year) was 0.29%. Drinking 50g milk will increase the risk by 7%, so how much will the incidence increase? Take each group 10000 people as an example. Under normal circumstances, 10000 is 0.29; In addition, 65438+100000 people drink milk, and 65438+100000 people are x people. The calculation is as follows: [x/(10000-x)]/[0.29/(10000-0.29)] =1.07, x = 0. 65438+100000 people increased by 0.02, which is equivalent to an increase of 2 people per 65438+100000 people. How to treat this risk?