Can Eating Dairy Affect Your Cancer Risk?

Milk and cookies, mac and cheese, yogurt parfaits, ice cream sundaes — classic comfort foods and treats are often packed with dairy. Dairy contains important nutrients, including calcium, vitamins, protein, and zinc. It can promote bone health and prevent bone loss. But the link between dairy and cancer risk isn’t simple.

“The challenge with studies that look at food and cancer risk is that some foods, like dairy, may prevent certain cancers but might also increase risk of other cancers. Cancer is not one disease, so the risk factors for different cancers are very different,” said Suneel D. Kamath, MD, an American Society of Clinical Oncology (ASCO) expert and an oncologist at the Cleveland Clinic.

Dairy and colorectal cancer risk

Research has shown that dairy reduces the risk of colorectal cancer. In a recent study of women in the United Kingdom, a diet rich in calcium and dairy was found to reduce the risk of colorectal cancer by 17%.

"The findings around the impact of dairy and calcium intake on colorectal cancer are striking,” said Dr. Kamath. “This study shows that for both dairy and calcium intake, as the amount consumed increases, the protective effect against colorectal cancer gets better and better. This is called a dose-response relationship. It is always encouraging when that is shown because it further validates the findings that dairy and calcium consumption can reduce colorectal cancer risk.”

But Dr. Kamath also noted that the study has limitations. It included only women from the U.K. It didn’t study how dairy impacts cancer risk in other parts of the world. People from many Asian countries, for example, often have problems digesting dairy. However, the U.K. study helps to confirm what previous studies have shown: High dairy consumption may be associated with a lower risk for developing and dying from colorectal cancer.

Dairy and breast cancer risk

Research into how dairy affects breast cancer risk has also shown mixed results. One large study in the United States looked at data from women who took part in the Nurses’ Health Study from 1980 to 2018. The research found that eating dairy did not impact overall breast cancer risk. The study also found:

• The amount of milk the study participants drank as teenagers affected their cancer risk. Women who reported drinking between 14 and 21 servings of milk per week as teens had a slightly higher risk of breast cancer.
• Women who reported eating more cheese during adulthood had a slightly lower risk of breast cancer.
• The risk varied by subtype. Women who reported drinking milk during adulthood before menopause had a slightly lower risk of estrogen receptor-positive breast cancer. However, they also had a slightly higher risk of estrogen receptor-negative breast cancer.

Dairy and prostate cancer risk

Eating a lot of dairy may increase the risk of prostate cancer. A review of research that analyzed a number of studies from different countries found that:

• Most of the studies found some link between drinking milk and an increased risk of prostate cancer.
• Both nonfat and higher-fat dairy were associated with an increased risk of prostate cancer.

Tips for including dairy in a healthy diet

Overall, research shows that dairy can lower the risk of some cancers and increase the risk of others. This is why no organizations have developed guidelines about eating dairy as it relates to cancer risk. To include dairy and calcium in your diet in a healthier way, follow these tips:

• Choose mainly low-fat or nonfat dairy, but be mindful that some may contain unhealthy added fillers or thickeners to replace the fat.
• Look for dairy products without added sugar or other sweeteners.
• Greek yogurt and cottage cheese can be great choices. Both contain a lot of protein and calcium.
• To meet daily calcium goals, try non-dairy sources of calcium. Examples include beans and lentils, leafy greens, fortified soy milk, and other milk alternatives.

Dr. Kamath is a member of ASCO’s Patient Information Editorial Board