Development and validation of a photographic atlas of food portions for accurate quantification of dietary intakes in China.

BACKGROUND: Accurate estimation of food portion sizes remains an important challenge in dietary data collection. The present study aimed to develop a food atlas with adequate visual reference to improve the accuracy of dietary surveys in China. METHODS: A food atlas for dietary surveys in China was developed using three visual reference systems, namely, regularly placed food portions, the two-dimensional background coordinates and common objects known in daily life. The atlas was validated by estimating a meal before and after using the food atlas, and differences in weight estimation were compared using a paired t-test. In total, 50 college students participated in the study. RESULTS: After determination of food varieties; design of the food display; purchase, processing, cooking and weighing of food; photographing food; post-image processing and data processing, a total of 799 pictures of 303 types of food and two types of tableware were produced. The mean value of food weight estimated with the atlas was closer to the actual weight, and the variation range of these values was smaller and more stable than that estimated without the atlas. The differences estimated before and after using the atlas for all foods were significant (P < 0.05). Comparing the differences in weight before using the atlas, the error ranges of food samples were reduced. CONCLUSIONS: A food atlas has been developed for a retrospective dietary survey in China, which can be used to enable a better understanding of nutritional adequacy in the Chinese population.

[Effects of vitamin A supplementation on nutritional status of iron in healthy adults].

OBJECTIVE: To investigate the effect of vitamin A (VA) supplementation on the nutritional status of iron in healthy adults. METHODS: One hundred and fifteen healthy adults were recruited and divided randomly into four groups, with 28 or 29 adults in each group. VA supplements with different doses of retinyl acetate in capsules were given for 4-month. The equivalent doses of supplemented retinyl acetate were 600 microg/d, 400 microg/d, 200 microg/d and 0 microg/d (control) of retinol, respectively. The capsules were administered orally by double blind method. During the experiment, the subjects kept their usual dietary pattern but avoided high VA or pre-VA carotenoids foods from their diets. A 24-h dietary recall was carried out monthly on every subject. Before and after the intervention, the fast blood samples were collected from each subject, and were determined for hemoglobin concentration, levels of serum retinol, iron, ferrtin and transferrtin receptor. RESULTS: Total 108 subjects finished the experiment, with 27, 28, 27 and 26 persons left in group A, B, C and D, respectively. The subjects from each group had similar dietary intakes of energy nutrients, VA and iron (both were P > 0.05) during the experimental period. The serum retinol concentration of subjects from group A increased from 1.63 +/- 0.55 micromol/L of baseline to 1.93 +/-0.52 micromol/L at the end of the experiment (P < 0.05). The elevated value of serum retinol for group B and C were 0.29 micromol/L and 0.14 micromol/L (both were P < 0.05). There was no difference before and after the experiment for control group D (P > 0.05). There was no significant difference on Hb concentration before and after the experiment as well as between groups (all were P > 0.05). In subjects of group A, serum iron concentration increased (P < 0.05) and serum ferrtin and transferrtin receptor concentration decreased significantly (both were P < 0.05) after VA supplement intervention. No such changes were observed in group B and C (P < 0.05). CONCLUSION: It seems that the intervention of VA supplement with relative high dose of retinol at dietary level could enhance the iron status further in no-anemic healthy adults even without dietary iron supplementation.