Dairy foods have their pros and cons; though they are a good source of calcium, they can also be high in fat. When it comes to the effects of dairy foods on breast cancer risk, a new study finds that they can be just as conflicting.

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Researchers suggest that a high intake of certain cheeses, such as cheddar, may raise women’s risk of breast cancer.

Researchers have found that eating high amounts of cheddar and cream cheeses may increase women’s risk of breast cancer, but a high intake of yogurt may reduce risk of the disease.

Lead study author Susan McCann, Ph.D., of the Department of Cancer Prevention and Control at Roswell Park Cancer Institute in Buffalo, NY, and colleagues recently reported their findings in the journal Current Developments in Nutrition.

Breast cancer is the most common cancer among women in the United States, after skin cancer. In 2017, there are expected to be around 252,710 new cases of invasive breast cancer diagnosed in women, as well as more than 40,000 deaths from the disease.

Diet is known to play a key role in breast cancer risk. Medical News Today recently reported on a study linking a poor diet during adolescence and early adulthood to a greater risk of premenopausal breast cancer.

Though some dairy products might fall under the umbrella of an unhealthful diet, research assessing the impact of dairy foods on breast cancer risk has produced inconsistent results; some studies have linked dairy intake to greater breast cancer risk, while others have indicated the opposite.

“This complexity is probably not unexpected, as dairy foods are complex mixtures and include several nutrients and non-nutrient substances that could potentially influence cancer etiology, through either increases or decreases in risk,” say McCann and colleagues.

For their study, McCann and team reviewed 2003-2014 data from the Roswell Park Data Bank and BioRepository, which included 1,941 women with breast cancer and 1,237 women without the disease.

All women completed a food frequency questionnaire that detailed the amount of total dairy products and individual dairy products – including cheese, yogurt, and milk – they consumed each month.

After adjusting the results for a number of possible confounding factors, including age, body mass index (BMI), menopausal status, and a family history of breast cancer, the researchers found that a high total dairy intake was associated with a 15 percent lower breast cancer risk.

This reduction in breast cancer risk was primarily attributable to a high yogurt intake; women who consumed high amounts of yogurt were found to have a 39 percent lower risk of developing breast cancer.

However, a higher intake of cheese – particularly cheddar cheese and cream cheese – had the opposite effect, posing a 53 percent increased risk of breast cancer.

Further studies are needed to gain a better understanding of how dairy foods affect breast cancer risk, but the researchers believe that their current findings shed some light.

“This study of the differences among women and their consumption of dairy products offers significant new understanding into the potential risk factors associated with breast cancer.

While diet is thought to be responsible for 30 percent of all cancers, we hope that further research will help us to more fully understand which food products are most valuable in terms of reducing risk for this disease.”

Senior author Christine Ambrosone, Ph.D., chair of the Department of Cancer Prevention and Control

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