Your Genetics Could Determine If Dairy Is Linked to Cancer Risk

Since childhood, many of us have been told to eat dairy foods every day to support our bone health, thanks to the calcium, magnesium, and other bone health-supporting nutrients that this food group provides. In fact, the most recent Dietary Guidelines for Americans recommending that most adults in the U.S. consume three dairy servings every day.

Milk, yogurt, kefir, and other dairy foods provide important nutrients like protein, calcium, vitamin B12, and riboflavin. And data shows that consuming these foods is linked to a slew of health benefits, including a reduced risk of bone fracture, healthy blood pressure, and better sleep quality.

But recent data published in BMC Medicine is showing that, along with all of the positives that are associated with eating dairy foods, there may be a potential downside to including this food group in your diet as well. Specifically, results show that, among a sample of Chinese adults, those who ate more dairy foods appear to have a higher risk of developing female breast cancer and liver cancer.

Dairy and Cancer Risk

Estimates suggest over 18 million people have cancer throughout the world. It is well established that certain dietary practices can play a role in cancer risk. While some data shows a potential link between eating dairy foods and either a protective or enhanced cancer risk (depending on the type of cancer), most studies are based on data from Western subjects. And since the genetic ability to metabolize dairy products differs when comparing those of Eastern vs. Western descent, it is critical to evaluate whether this potential link remains when people who reside in the Eastern part of the world consume dairy foods.

Because of this knowledge gap, researchers evaluated the associations between dairy consumption with total and site-specific cancer incidence among Chinese subjects.

Using a large sample size from The China Kadoorie Biobank (CKB) study, a large nationwide prospective cohort study of Chinese adults, researchers evaluated half a million subjects’ dairy intake and cancer incidence to evaluate whether the two are related. During an average follow-up of 10.8 years, overall, 20.4% of participants reported consuming dairy products (mainly milk) at least one day every week.

The researchers showed a trend associated with consuming more dairy and a risk of developing certain cancers. For each additional 50 grams of dairy products, there was a 12% greater risk of developing liver cancer and a 17% greater risk of developing breast cancer. And although the data was not statistically significant, regular dairy consumption was associated with an increased risk of lymphoma.

Researchers did not observe a higher risk of colorectal, prostate, or other cancer in tandem with increased dairy intake.

The observed associations were independent of other lifestyle factors.

Study Limitations

This large-scale study is significant, especially since dairy intake appears to be becoming more popular in China.

But as Erin Coffield, RDN, vice president of health and wellness communications for the National Dairy Council, told Verywell, this study does have some limitations, including:

1. The researchers “did not control for energy (i.e., calories) and some other factors that are linked with cancer, especially in this population (e.g., poor air quality),” Coffield said.
2. The subjects “consume very low levels of dairy, so from a physiology perspective there is a question of how such low intakes of dairy would lead to these increases,” she added. “And only 20% of the study participants consumed this low amount of dairy—at least one serving per week.”

Maria Kakkoura, PhD, MSc, first author of the study and a nutritional epidemiologist at Oxford Population Health, said that “the observational nature of the current study does not allow us to confirm that the associations we have found are indeed causal,” highlighting yet another limitation.

“We don’t know exactly which components of dairy products are the driving factors [for cancer risk],” she told Verywell. “On the other hand, dairy products are an important source of protein, vitamins and minerals. It would not be prudent to reduce dairy consumption based solely on the results from the current study or without ensuring adequate intake of protein, vitamins and minerals from other sources.”

How to Reduce Cancer Risk

Cancer is an unfortunate outcome that can be a result of a variety of factors, many of which are completely out of our control (like our family history). The good news is that, while it won’t guarantee that you live a long and cancer-free life, there are some lifestyle choices that you can make to reduce your risk of developing certain cancers, including:

• Avoiding tobacco
• Maintaining a healthy weight
• Participating in physical activity
• Avoiding processed meat
• Eating folate foods, like avocado, oranges, and green leafy vegetables
• Limiting or avoiding alcohol intake

When it comes to dairy’s role in cancer risk, the American Institute for Cancer Research (AIRC) and World Cancer Research Fund (WCRF) published a report in 2018 that evaluated the scientific evidence linking diet, nutrition, physical activity, and cancer.

“They point out that it is important to have a holistic focus, rather than focusing on specific foods affecting cancer risk, people should look to healthy dietary patterns and physical activity habits to form a healthy way of living to help reduce risk,” Coffield said.

Some highlights of the report include:

• Consumption of dairy products probably protects against colorectal cancer.
• Consumption of dairy foods was not linked to total cancer risk
• Consumption of dairy foods was associated with lower risk of premenopausal breast cancer
• Diets high in calcium decreased the risk of pre- and postmenopausal breast cancer
• There is limited evidence that higher consumption of dairy products is linked to risk of prostate cancer, thus requiring additional research
• There is no conclusion when it comes to dairy and ovarian cancer and liver cancer

“Overall evidence to date on whether eating dairy products affects the risk of cancer has been inconsistent,” Kakkoura said. “In addition to performing similar large-scale association studies in various populations, it is more important to explore the underlying mechanisms linking dairy products and cancer incidence.”