Consuming high-fat dairy products following diagnosis with breast cancer could lead to a higher risk or worse outcomes, according to new research.
The study, published in the Journal of the National Cancer Institute, finds that breast cancer patients who consume high-fat dairy products following diagnosis increase their chances of dying from the disease years later.
"Specifically, women consuming one or more servings per day of high-fat dairy had a 64% higher risk of dying from any cause and a 49% increased risk of dying from their breast cancer during the follow-up period," said Dr Candyce Kroenke from the Kaiser Permanente Division of Research, USA.
The findings are said to be the first to examine the relationship between high- and low-fat dairy consumption following a diagnosis of breast cancer and long-term breast cancer survival.
"Women have been clamouring for this type of information," said Dr Susan Kutner, chair of the Kaiser Permanente Northern California Regional Breast Care Task Force.
Kunter said that the new findings will boost the advice that breast cancer patients are given to reiterate the importance of a low-fat diet, as well as exercise and weight management, in preventing recurrence of the disease.
“They're asking us, 'Tell me what I should eat?' With this information, we can be more specific about recommending low-fat dairy products." she said.
Kroenke and her team noted that previous studies have suggested that higher lifetime exposure to oestrogen is a causal pathway to breast cancer – adding that oestrogen levels are believed to be elevated in dairy products consumed in the Western world because most of its milk comes from pregnant cows.
In the new study, the team analysed data from a cohort of 1,513 women who were diagnosed with early-stage, invasive breast cancer. The women were asked about their dietary habits and were then tracked to monitor cancer outcomes for an average of 12 years.
The category of high-fat dairy products researchers tracked included cream, whole milk, condensed or evaporated milk, pudding, ice cream, custard, flan, and also cheeses and yogurts that were not low-fat or non-fat.
Overall, low-fat dairy intake was greater (an average of 0.8 servings per day) than high-fat dairy (0.5 servings per day).
In general, women reported that they consumed low-fat milk and butter most often, and they consumed relatively limited amounts of low-fat dairy desserts, low-fat cheese and high-fat yogurt.
However, the team found that those consuming larger amounts of high-fat dairy – defined as one serving or more per day – had "higher breast cancer mortality as well as higher all-cause mortality and higher non-breast cancer mortality."
No association was found between low-fat dairy products and breast cancer outcomes.