July 12, 2024

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Does Milk Really Cause Breast Cancer and Promote Tumor Grow?

Does Milk Really Cause Breast Cancer and Promote Tumor Grow?

Does Milk Really Cause Breast Cancer and Promote Tumor Grow?

Recently, a study published in BMC Medicine added important evidence to the impact of dairy consumption on cancer among Chinese people.

Data from more than 10 years of follow-up of 500,000 people in different regions of China show that among Chinese adults, higher intake of dairy products is associated with higher risks of liver cancer, female breast cancer, and overall cancer [1] .

Does Milk Really Cause Breast Cancer and Promote Tumor Grow?

Image source: BMC Medicine

Let’s discuss details!

Does Milk Really Cause Cancer?

The article discusses whether milk can potentially lead to cancer.

The research paper emphasizes that the study has certain limitations, such as only collecting data on the intake of a portion of major food groups in the questionnaire survey, without considering total energy, specific nutrients (such as SFA and calcium), or the intake of specific dairy products.

Furthermore, although a large number of cancer cases were recorded, the statistical power for some less common cancer sites (such as prostate cancer) remains low.

Even for common cancer types, the number of cases may not be sufficient to draw reliable results in subgroup analysis (e.g., assessing breast cancer risk related to estrogen receptor status).

In simple terms, the research team also objectively states in the paper that, despite adjusting for a range of confounding factors, the study is not enough to confirm a causal relationship between milk consumption and cancer.

There are three hypotheses regarding milk causing cancer:

  1. Milk contains insulin-like growth factor-1 (IGF-1), which has been shown to promote the growth of breast cancer cells in in vitro experiments.

  2. Casein in milk may be carcinogenic. Based on a “rat experiment” in the United States, rats were fed either soy protein or casein while being exposed to aflatoxin. The results showed that the rats in the casein group had more liver cancer cases than those in the soy protein group, leading to the belief that casein is a carcinogen.

  3. Dairy products have a higher fat content, and an increase in saturated fat intake may increase the risk of breast cancer.

At first glance, these hypotheses seem reasonable, but further examination reveals their flaws.

First, IGF-1 is a peptide protein similar to insulin that is naturally produced by the human body and plays a significant role in the synthetic metabolism of humans and infants. The amount of IGF-1 in commonly available milk is only 2.45 ng/mL, which is negligible compared to what the human body produces daily.

Agencies like the FDA and the World Health Organization do not have any evidence to suggest that IGF-1 is a carcinogenic factor.

As for casein, the “rat experiment” fails to consider a crucial factor – aflatoxin is a potent carcinogen on its own. Therefore, this experiment cannot directly conclude that casein is carcinogenic.

Regarding the third hypothesis, a meta-analysis of milk and breast cancer risk suggests that the association between milk and breast cancer risk is primarily due to correlations between nutrients in the diet. In other words, people who consume more milk may also have a high intake of meat and other high-fat foods, which could increase their risk of breast cancer.

For example, the consumption of milk is much higher in Western populations compared to Asian populations, and Western populations also consume more meat. However, it is challenging to distinguish whether it is the fat from milk or fat from other food sources that may contribute to this increased risk.

In conclusion, based on the current state of research, it is not possible to definitively establish a clear connection between milk and cancer. The question of whether milk causes cancer is still open, and further research is needed in the future.

Moreover, even if milk poses a cancer risk, it is essential to consider the dosage. Science has long established that only the dosage can determine whether a substance is toxic or carcinogenic, even in the case of seemingly harmless foods like white rice.

In summary, the current consensus in the field of nutrition affirms that milk is a “nutrient-rich food,” and cancer patients can certainly consume it in moderation.

Does Milk Really Cause Breast Cancer and Promote Tumor Grow?



[1] Kakkoura, MG, Du, H., Guo, Y. et al., (2022). Dairy consumption and risks of total and site-specific cancers in Chinese adults: an 11-year prospective study of 0.5 million people. BMC Med 20, 134 (2022). https://doi.org/10.1186/s12916-022-02330- 3

[2]Curr Dev Nutr. 2019 Jun 13;3(Suppl 1):P05-026-19.


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