I don’t strive to bring attention to null experimental results because I am fundamentally a killjoy. I do it because null results are important. They belong on the scale of rationality when we consider, for example, the efficacy of the latest super-food, super-drink or super-herb, as the case may be.
In this case, we’re talking green tea. The headline and first paragraph to the ScienceDaily piece say it – Green Tea of No Use in Breast Cancer Prevention, Large Study Finds
Green tea does not protect against breast cancer. A study of data from approximately 54,000 women, published in BioMed Central’s open access journal Breast Cancer Research, found no association between drinking green tea and breast cancer risk.
Certainly, this finding does not tell us that green tea is useless, with no health benefits at all. It does, however, counter-balance other information out there. Research team leader, Motoki Iwasaki (National Cancer Center, Tokyo), explained:
“Although in vitro and animal-based studies have suggested that green tea may have beneficial protective effects against breast cancer, results from human studies have been inconclusive. Our large-scale, population-based prospective cohort study is one of the first to include a wide range of tea intakes; women who drank green tea less than 1 cup per week to those who drank 10 or more cups per day. It found no overall association between green tea intake and the risk of breast cancer.”
So yes, put this null result, the absence of a positive association, on the scale of whether or not green tea works to prevent breast cancer. It carries quite a bit of weight, even though it is null.