MILAN – New research suggests that drinking coffee or tea after breast cancer treatment may improve survival. In a study of 8,900 women with stage 1, 2 or 3 breast cancer, those who drank coffee survived longer after a breast cancer diagnosis than those who did not drink coffee. Both coffee and tea were linked to improved survival from any cause.
Several factors were linked to greater coffee or tea consumption, so this finding must be taken with some caution.
The study, funded by AICR and published in the British Journal of Cancer, adds to a growing body of research on how diet affects breast cancer survivors’ health.
The study included 8,900 women who had been diagnosed with breast cancer. The women were part of the Nurses Health Studies and they had completed questionnaires about their dietary habits — along with other lifestyle and relevant factors — every four years.
Lead author and AICR grantee Maryam Farvid, PhD., and her colleagues, calculated averages of the women’s coffee and tea habits at least a year after diagnosis and every four years thereafter.
During the study, 1,054 participants died of breast cancer and 2,501 died of any cause (including breast cancer). Participants drank 1.7 cups of coffee and 0.7 cups of tea daily on average after their breast cancer diagnosis.
Drinking coffee lowers the risk of dying from breast cancer
Participants who drank coffee after their breast cancer diagnosis survived longer than participants who did not drink coffee. The more coffee they drank, the more their chance of breast cancer survival improved. Participants who drank coffee also had fewer deaths from any cause.
Drinking tea and the risk of dying from breast cancer
Participants who drank more tea had a lower risk of dying from any cause than those who did not drink tea. (Their breast cancer survival was not improved or worsened.)
Coffee drinking before breast cancer diagnosis was not linked to breast cancer survival
Coffee and tea consumption before a breast cancer diagnosis was not linked to breast cancer-specific death. In other words, how much coffee a person drank before diagnosis did not affect their breast cancer survival. One exception was an increased risk among participants who drank more coffee before being diagnosed but drank less coffee after they were diagnosed.
Decreasing coffee consumption after breast cancer diagnosis increased risk
Participants who lowered their coffee intake from more than two cups per day before breast cancer diagnosis to no coffee after diagnosis had a 91 percent higher risk of breast cancer-related death than participants who did not drink coffee before or after a breast cancer diagnosis.
Participants who lowered their coffee intake from more than two cups per day before breast cancer diagnosis and then drank less (up to 2 cups of coffee each day) after diagnosis had a 34 percent higher risk of breast cancer-related death than participants who did not drink coffee before or after a breast cancer diagnosis.
Other factors may influence the risk of breast cancer death among coffee drinkers
Researchers mentioned several factors with impacts on survival that could not be separated from coffee or tea intake. Participants with higher coffee consumption after diagnosis were also:
- more likely to drink more alcohol, smoke, consume more animal fat and use aspirin more frequently after diagnosis.
- less likely to have radiotherapy or chemotherapy.
Researchers tried to account for the potential effect of other factors in their analysis. However, the findings regarding coffee or tea consumption may be due in part to these confounding factors.
Researchers noted that several factors did not contribute to the effects observed, including:
- age
- body mass index (BMI) after breast cancer diagnosis
- stage of cancer
- amount of coffee or tea consumed on average before breast cancer diagnosis
