title: An internet-based food frequency questionnaire for a large Chinese population.
abstract: OBJECTIVE
  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.
  
  
  METHODS
  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.
  
  
  RESULTS
  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.
  
  
  CONCLUSIONS
  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/.
authors.affiliation: Department of Nutrition and Food Hygiene, School of Public Health, Harbin Medical University, Harbin, Heilongjiang, China.|National Key Discipline, Harbin Medical University, Harbin, Heilongjiang, China.
authors.forename: Ren-Nan
authors.initials: RN
authors.lastname: Feng
authors.affiliation: Department of Nutrition and Food Hygiene, School of Public Health, Harbin Medical University, Harbin, Heilongjiang, China.|National Key Discipline, Harbin Medical University, Harbin, Heilongjiang, China.
authors.forename: Shan-Shan
authors.initials: SS
authors.lastname: Du
authors.affiliation: Department of Nutrition and Food Hygiene, School of Public Health, Harbin Medical University, Harbin, Heilongjiang, China.|National Key Discipline, Harbin Medical University, Harbin, Heilongjiang, China.
authors.forename: Yang
authors.initials: Y
authors.lastname: Chen
authors.affiliation: Department of Nutrition and Food Hygiene, School of Public Health, Harbin Medical University, Harbin, Heilongjiang, China.|National Key Discipline, Harbin Medical University, Harbin, Heilongjiang, China.
authors.forename: Zhen
authors.initials: Z
authors.lastname: Li
authors.affiliation: Department of Nutrition and Food Hygiene, School of Public Health, Harbin Medical University, Harbin, Heilongjiang, China.|National Key Discipline, Harbin Medical University, Harbin, Heilongjiang, China.
authors.forename: Ying-Feng
authors.initials: YF
authors.lastname: Zhang
authors.affiliation: Department of Nutrition and Food Hygiene, School of Public Health, Harbin Medical University, Harbin, Heilongjiang, China.|National Key Discipline, Harbin Medical University, Harbin, Heilongjiang, China.
authors.forename: Chang-Hao
authors.initials: CH
authors.lastname: Sun
authors.affiliation: 3College of Bioinformatics Science and Technology, Harbin Medical University, Harbin, Heilongjiang, China. Email: jiangyongshuai@gmail.com.
authors.forename: Yong-Shuai
authors.initials: YS
authors.lastname: Jiang
mesh_terms: D000328:Adult; D002681:China; D015930:Diet Records; D004034:Diet Surveys; D002149:Energy Intake; D005260:Female; D005502:Food / Q000145:classification; D006801:Humans; D020407:Internet; D008297:Male; D015596:Nutrition Assessment; D009753:Nutritive Value; D015203:Reproducibility of Results; D011795:Surveys and Questionnaires