I’ve been seeing a few news reports recently regarding nut consumption, particularly walnuts, and diabetes. The reports are based on a study Walnut Consumption Is Associated with Lower Risk of Type 2 Diabetes in Women. This study used data from the Nurses’ Health Study to determine the effect of nut consumption on diabetes risk.
The news article all proclaim that regular consumption of walnuts can reduce the risk of developing type 2 diabetes. There was a risk reduction shown with consumption of walnuts as little as once a month but the greatest risk reduction (24% in comparison to women who ate few or no nuts) was seen in the women who ate walnuts at least once a week.
Now, as much as I’m a fan of nuts, I’m always a little skeptical of reports such as this. I always wonder if the news reports accurately reflect the study’s findings and if the study is well-designed. So… I went and took a look at the journal article.
I’m immediately wary of any study that uses food frequency questionnaires to obtain data on food consumption. These questionnaires are notoriously inaccurate. Putting that issue aside and looking at the rest of the study, a couple of additional issues popped out at me. While the researchers controlled for things such as physical activity, fruit and vegetable consumption, and obesity, it is impossible to control for all variables and it’s possible that a factor common to the walnut eating group other than their walnut consumption may have reduced their risk of diabetes. Also, after controlling for BMI, the risk reduction afforded by walnut consumption dropped from the reported 24% to 15%. Perhaps if another measure, such as waist-to-hip ratio had been used this percentage would have decreased further.
Most importantly: funding for the study was provided by the California Walnut Commission.
I certainly don’t want to discourage anyone from eating walnuts. However, too much of any one thing can be bad for us and I don’t want anyone reading reports from this study erroneously thinking that they should be consuming unlimited quantities of walnuts to stave off type 2 diabetes. There are benefits to all nuts and they all contain fairly concentrated calories so it’s certainly possible to go overboard with them. Incorporate a variety of nuts in your diet to obtain the maximum health benefits from their consumption.