Miller Tracy M, Abdel-Maksoud Madiha F, Crane Lori A, Marcus Al C, Byers Tim E
Department of Preventive Medicine and Biometrics, University of Colorado Denver, 4200 East 9th Avenue, Denver, CO, 80262, USA.
Nutr J. 2008 Jun 27;7:18. doi: 10.1186/1475-2891-7-18.
Self-reports of dietary intake in the context of nutrition intervention research can be biased by the tendency of respondents to answer consistent with expected norms (social approval bias). The objective of this study was to assess the potential influence of social approval bias on self-reports of fruit and vegetable intake obtained using both food frequency questionnaire (FFQ) and 24-hour recall methods.
A randomized blinded trial compared reported fruit and vegetable intake among subjects exposed to a potentially biasing prompt to that from control subjects. Subjects included 163 women residing in Colorado between 35 and 65 years of age who were randomly selected and recruited by telephone to complete what they were told would be a future telephone survey about health. Randomly half of the subjects then received a letter prior to the interview describing this as a study of fruit and vegetable intake. The letter included a brief statement of the benefits of fruits and vegetables, a 5-A-Day sticker, and a 5-a-Day refrigerator magnet. The remainder received the same letter, but describing the study purpose only as a more general nutrition survey, with neither the fruit and vegetable message nor the 5-A-Day materials. Subjects were then interviewed on the telephone within 10 days following the letters using an eight-item FFQ and a limited 24-hour recall to estimate fruit and vegetable intake. All interviewers were blinded to the treatment condition.
By the FFQ method, subjects who viewed the potentially biasing prompts reported consuming more fruits and vegetables than did control subjects (5.2 vs. 3.7 servings per day, p < 0.001). By the 24-hour recall method, 61% of the intervention group but only 32% of the control reported eating fruits and vegetables on 3 or more occasions the prior day (p = 0.002). These associations were independent of age, race/ethnicity, education level, self-perceived health status, and time since last medical check-up.
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.
在营养干预研究中，饮食摄入量的自我报告可能会受到受访者倾向于按照预期规范回答的影响（社会赞许性偏差）。本研究的目的是评估社会赞许性偏差对使用食物频率问卷（FFQ）和24小时回忆法获得的水果和蔬菜摄入量自我报告的潜在影响。
一项随机双盲试验比较了暴露于潜在偏差提示的受试者与对照受试者报告的水果和蔬菜摄入量。受试者包括163名年龄在35至65岁之间居住在科罗拉多州的女性，她们通过电话随机选择并招募，被告知要完成一项关于健康的未来电话调查。然后，随机抽取一半受试者在访谈前收到一封信，将其描述为一项关于水果和蔬菜摄入量的研究。这封信包括水果和蔬菜益处的简要说明、一张“一天五份蔬果”贴纸和一个“一天五份蔬果”冰箱贴。其余受试者收到相同的信，但仅将研究目的描述为一项更一般的营养调查，既没有水果和蔬菜相关信息，也没有“一天五份蔬果”材料。然后，在信件发出后的10天内，通过电话对受试者进行访谈，使用八项FFQ和有限的24小时回忆法来估计水果和蔬菜摄入量。所有访谈者均对治疗情况不知情。
通过FFQ方法，看到潜在偏差提示的受试者报告的水果和蔬菜摄入量高于对照受试者（每天5.2份对3.7份，p<0.001）。通过24小时回忆法，干预组61%的受试者报告前一天吃了3次或更多次水果和蔬菜，而对照组只有32%（p=0.002）。这些关联独立于年龄、种族/民族、教育水平、自我感知的健康状况以及上次体检后的时间。
使用食物频率问卷或有限的24小时回忆法进行的水果和蔬菜摄入量自我报告都容易受到显著的社会赞许性偏差影响。营养干预试验中干预效果的有效评估可能需要对饮食变化进行客观测量。
