Readers of various health news articles could be forgiven if they rush out to buy their young daughters peanuts and peanut butter. Headlines touting the efficacy of such consumption for improving breast health are all over the internet. That s not quite the whole story, though.
The study that gave rise to all this peanut worship wasn t really just about peanuts. And it s even questionable whether peanut butter has anything to do with what the headlines suggest.
Researchers from Washington University in St. Louis and Harvard Medical School investigated whether vegetable protein and vegetable fat intake in pre-adolescent and adolescent girls was linked to the risk of benign breast disease (BBD) (breast cysts, for example) in later life. They found that increased consumption of peanuts, peanut butter, lentils, beans, and corn was associated with lower risks of breast disease later in life.
The investigators administered food frequency questionnaires every year to over 9,000 pre-adolescent and adolescent girls 9-15 years old in 1996. The questionnaires were completed every year until 2001, and then every second year until 2010. Beginning in 2005, the young women who had reached 18-30 years of age reported whether or not they had been diagnosed with benign breast disease after a breast biopsy.
As reported by various news outlets, consumption of peanuts and peanut butter was associated with a much lower risk of BBD, but so was consumption of other good sources of vegetable protein and fat. Overall, consuming any of those sources was linked to a 38 percent decrease in the risk of BBD.
The problem with this study is that it s observational, and thus can t do more than suggest hypotheses for further research. There s no way one can say that consumption of vegetable proteins and fats actually causes a lower risk of BBD. But you wouldn t know that from the headlines.
While nuts, beans and lentils are healthful foods, ACSH s Dr. Ruth Kava commented, we can t say from this study that they really have a preventive role. To do that, one would have to run a controlled trial to compare BBD outcomes in girls who did or did not eat good sources of vegetable protein and fat. She continued It s unlikely that such a trial would be ethical in young girls and women, since withholding healthful foods from them to set up a control group would probably not be approved by the relevant Institutional Review Boards. Also, it should be noted that peanuts and peanut butter will really pack on the calories, so we hope that girls won t go rushing out to stuff PB&J into their lunch boxes willy-nilly.