Some studies suggest people under-report their caloric intake by 30 percent…or more. But when it comes to fruits and vegetables however, it appears that people are lying in the other direction — stating that they consume far more of the colorful critters than they really do.
The finding, reported in the current Nutrition Journal, suggests the data the health community has collected on fruit and vegetable consumption are tainted by “approval bias.” The bias? We know we are expected to eat five or more servings of fruits and vegetables a day, so that’s what we say when we are asked, and we may even really believe it to be true.
Our results show that self-reports of fruit and vegetable intake by means of both food frequency questionnaires and 24-hour recall are susceptible to substantial social approval bias. Attention to this bias in the context of dietary reports from subjects in nutritional intervention studies is an important consideration in study design, analysis, and interpretation. Continued efforts to improve methods to objectively evaluate nutritional interventions are needed.
It needs be pointed out that the study results were only obtained from a small sample of the Colorado female population.
We were therefore unable to assess the impact of reporting bias among men, or among subgroups defined by age, race/ethnicity, or socioeconomic status. Future work should examine effects in such subgroups…
Nonetheless the conclusion was this:
Self-reports of fruit and vegetable intake using either a food frequency questionnaire or a limited 24-hour recall are both susceptible to substantial social approval bias. Valid assessments of intervention effects in nutritional intervention trials may require objective measures of dietary change.
Now off to eat your veggies!