The Nurses Health Study and the Nurses Health Study II are studies which collect extensive questionnaire data prospectively, including data about diet. The study now contains well over 200,000 female nurses. Questionnaires were completed every six months initially and then every 2 to 4 years thereafter. Researchers from the Harvard school of Epidemiology and Public Health had previously published a study finding that fruit juice and foods with high glycemic index were associated with breast cancer survival as well as all-cause survival. Consequently, the same researchers began a study of the association between sugar sweetened beverages (SSB) and artificially sweetened beverages (ASB) in women who had been previously diagnosed with breast cancer. They wanted to relate the consumption of these beverages to the mortality from breast cancer (breast cancer-specific mortality) and from mortality in general (all-cause mortality). Their theory that these beverages may impact mortality was strengthen by their previous study.

During a median follow-up of 11.5 years, 8863 eligible women nurses were diagnosed with breast cancer. The researchers found that post-breast cancer diagnostic SSB consumption was associated with a higher breast cancer-specific mortality. During this time period, there was a 31% increase in breast cancer-specific mortality in those women using 1 to 3 servings of SSB per week and 35% greater in those having greater than three servings per week. Using this data, the authors were able to calculate that there were 56.3 additional deaths per 10,000 person-years of follow-up compared with women who did not drink SSBs. They were also able to calculate that there would be a proportional reduction in expected breast cancer-specific mortality of 10.5% if all women did not drink SSBs after the diagnosis of breast cancer and was 8.6% if all women consumed less than two servings of SSBs per month after diagnosis.

They found no difference in mortality based on whether the SSBs were carbonated or noncarbonated. They also found no difference between caffeinated and non-caffeinated SSBs. However, the researchers did note that replacing one serving of SSB per day with a similar serving of coffee or tea was associated with a 15 to 18% lower risk of breast cancer-specific mortality. The findings were similar for all-cause mortality.

In conclusion this very large process perspective study demonstrated that higher SSB consumption after breast cancer diagnosis was associated with breast cancer-specific and overall mortality risk among breast cancer survivors. Higher ASB consumption, in contrast, was not associated with higher breast cancer-specific or all-cause mortality.