So just how many servings of fruits and vegetables should we eat a day? To add to the numbers game, the media has recently reported on two different studies examining the impact of fruit and vegetable consumption on mortality with two quite different conclusions. First, I think its important to clarify how nutrition studies are done.
Studies that look at the impact nutrition has on mortality, cancer and cardiovascular disease are almost always cohort studies. This means thousands of people are asked to fill out a questionnaire or are interviewed about their daily food intake and then researchers estimate the number of servings per food type consumed on a daily basis. The same people are then followed for anywhere from 5 to 20 years and a comparison is made between the number of servings of specific food items and the outcomes mentioned above.
As I’m sure you can figure out, this type of study design could potentially lead to somewhat half-baked results because people are unlikely to be able to accurately recall their food intake and will often respond to questions in a way that makes them look as good as possible. Nutrition studies can also easily be influenced by confounding variables — people who eat more fruits and vegetables may also exercise more or smoke less. While researchers try to control for all of these factors, it is not possible to completely eliminate the problem.
Netherless, So how many servings a day should you eat? Well if it was me, I would base it on the evidence, how much I like fruits and vegetables, and overall, on how eating fruit and vegetables make me feel. In other words, use common sense.