An internet-based food frequency questionnaire for a large Chinese population.

National dietary surveys are needed and difficult to conduct in China. The current study aims to develop and validate an internet-based diet questionnaire for Chinese (IDQC) to assess intakes in Northern China.We recruited 292 city residents by email and telephone in Harbin to obtain the IDQC and 3-day diet diaries. The food group and nutrient intakes from the IDQC were validated against those from the 3-day diet diaries. Paired sample t-tests were used to compare the methodological differences, and repeatability was estimated using Pearson's correlations. Cross-classification was used to calculate the percentage agreement in quartiles for all food groups and nutrients.Positive correlations were found between the IDQC and 3-day diet diaries for all food groups after energy adjustment (from 0.28 for seeds and nuts to 0.63 for dairy products). Positive correlations were observed for all nutrients between the IDQC and 3-day diet diaries, with correlations ranging from 0.37 for folic acid to 0.98 for iodine. The overall agreements for food groups and nutrients were above 69.2%, indicating satisfactory consistency between the IDQC and 3-day diet diaries.The IDQC can be used to estimate the food and nutrient intakes in a Northern China population for both clinical nutrition epidemiological and public health nutritional purposes. The questionnaire system IDQC (v1.0) is freely available at http://www.yyjy365.org/diet/.背景与目的：在中国进行全国性膳食调查紧迫且难以实行。本研究的目的是建 立一个适用于中国人的网上膳食调查问卷（IDQC）并在北方人群中验证其有 效性。方法与研究设计：通过电子邮件和电话招募292 名哈尔滨居民，完成 IDQC 和3 天膳食日记。通过与3 天膳食日记中的数据比较，来验证IDQC 中 食物组和营养素的准确性。应用配对样本t 检验，比较两种调查方法中食物组 和营养素的平均水平，应用皮尔森相关系数分析问卷的重复性。将两种调查方 法中的食物组和营养素摄入量四等分后，应用交叉分组计算问卷一致率。结 果：校正总能量摄入后，所有食物组在IDQC 和3 天膳食日志间均呈正相关 （相关系数的变化范围从种子和坚果类的0.28 到奶制品的0.63）。所有营养 素在IDQC 和3 天膳食日志间仍然呈明显正相关，相关系数由叶酸的0.37 到碘 元素的0.98。食物组和营养素的一致率均在69.2%以上，表明IDQC 和3 天膳 食日志间有令人满意的一致性。结论：在中国北方，IDQC 能够用于临床营养 流行病学和公共健康目的的食物和营养素摄入量估计。问卷调查系统IDQC （v1.0）见：http://www.yyjy365.org/diet/。.