Modern, developed society is moving into an era of preventative healthcare. Instead of focusing only on how to cure diseases that people already have, researchers are increasingly concerned with determining how to prevent people from ever developing them. Because of the importance of diet in determining how healthy people are, a lot of preventative healthcare measures concern what people eat, and nuts are one food item that many scientists argue have lasting health benefits. One study done on people with diabetes claims that eating nuts, particularly tree nuts, can greatly reduce the chances of people developing cardiovascular diseases. Could eating nuts really decrease the likelihood of diabetic people developing heart issues?
The study, published by the American Heart Association, was done on 16,217 men and women with diabetes. The goal of the study was to compare the participant’s nut consumptions to their risk of developing cardiovascular diseases. Nut consumption of each participant was tracked using a validated food frequency survey, in which people had to input information about their dietary habits. Participants in the study updated their answers to the survey every two to four years. After collecting data about people’s food consumption, researchers did a follow up during which they assessed the frequency of cardiovascular disease and death in the participants. During the follow-up, scientists found 3,336 instances of cardiovascular disease and 5,682 deaths. The participants were broken up into categories based on their nut consumption. The health data was then compared between two groups of the participants, those who ate at least five servings of nuts every week and those who ate less than one serving of nuts every month. The authors of the study claim that people who increased their nut intake after being diagnosed with diabetes had an eleven percent lower risk of developing cardiovascular disease, a fifteen percent lower risk of developing coronary heart disease, a twenty-five percent lower cardiovascular disease mortality, and a twenty-seven percent lower overall mortality.
There are a few issues with the study that immediately stand out. For one, the authors provide no information about the sampling methods that they used. Although the sample size is relatively large, there are no clues as to whether the sample is truly representative of the population, everyone with diabetes in the United States. It is also concerning that the participants only had to update their food intake surveys every two to four years. People’s eating habits can vary quite a bit over the span of two years, and just because they ate a lot of nuts (or didn’t) for a few months out of one year does not mean that they consistently ate them (or didn’t) over four. To make this study’s results more conclusive, scientists should have tracked nut consumption much more frequently.
The researchers statistically controlled for a few outside causes of cardiovascular disease including sex/cohort, body mass index at diabetes diagnosis, smoking status, diabetes duration, nut consumption before diabetes diagnosis, and diet quality. In controlling for these variables, scientists can conclude that the changes in risk of cardiovascular disease that they observed was not caused by any of the factors listed above. Controlling for these variables was an important step, and the researchers argue that by controlling for these factors, they prove that the changes in cardiovascular disease rates were directly associated with nut consumption. However, the study needed to control for many other variables to ensure that they results that they got really were related to nut consumption. They should have also controlled for level of exercise, family history of diabetes and diet, and alcohol usage, just to name a few. It is possible that nut consumption is also related to these variables, and that there is no real association between nut intake and cardiovascular diseases.
The study’s questionable experimental and statistical design should make readers hesitant of their concluding claim. Although increased nut intake may decrease the risk of people with diabetes developing cardiovascular disease or dying, more research needs to be done before anyone can claim that there is a strong association between eating nuts and having a healthier heart.
Data/Society/Decision-making Spring 2019 