Back-ground level of dietary intake of tin among general Japanese population

2004 Fiscal Year Final Research Report Summary

• Project/Area Number: 13680662
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Single-year Grants
• Section: 一般
• Research Field: 環境保全
• Research Institution: Kyoto Women's Junior College
• Principal Investigator: SHIMBO Shinichiro Kyoto Women's Junior College, Professor, 教授 (60027406)
• Project Period (FY): 2001 – 2004
• Keywords: dietary intake of tin / determination of tin by ICP-MS / canned foods / general Japanese population / tin

Research Abstract

Part 1 Intake of tin through daily food. Aim : This study was initiated to measure dietary intake of tin among general Japanese population. Materials and Methods : Samples obtained from 501 subjects (245 men and 256 women at 40-77yrs) by means of 24-h food duplicate collection were wet-digested, and the digests were subjected to the determination of tin by inductively coupled mass spectrometry (ICP-MS). Results : Daily intake of tin was below the LOD (5ug/day, as defined by 3xASD of the reagent blank values) in 193 cases (38.5%). The intakes distributed in a wide range up to 5407 μg/day, and 40 subjects (8%) took more than 1mg tin/day. Assuming that the intake of <LOD cases be half a LOD or 2.5 μg/day, GM, GSD and median was 16.2 μg/day, 2.7, and 11.6 μg/day, respectively. There was no difference between the two sexes. Conclusions : Dietary intake of tin was about 16 μg/day when log-normal distribution was assumed, level being much lower than expected.
Part 2 Re-examination of dietary t in intake under strict quality control, with special reference to tin intake via canned foods. Aim : Knowing that acid reagents for wet-digestion contain tin at substantial levels, dietary intake of tin among general Japanese population was re-examined under strict quality controls, especially with the use of low-tin reagents. Materials and Methods : Preliminary examination of commercially available acid reagents disclosed that the tin contents were various subject to the suppliers. Accordingly, the acids of high quality (i.e., with the low tin contents) were selected for use at this stage of analysis with wet-digestion followed by ICP-MS. Food duplicate samples from 30 adult men and 81 adult women were subjected to the re-examination including wet-digestion and ICP-MS analysis. Results : A low LOD(<0.1 μg/day as defined by 3xASD of the reagent blank values) was established by use of the newly selected reagents. The distribution of daily tin intake was extremely biased so that it could not be normal even after logarithmic conversion. Daily intake of tin ranged from 1.5 to 2280 μg/day with a median of 5.3 μg/day among 30 adult men, where as it was 1.8 to 2291 μg/day with a median 5.7 μg/day among 81 adult women. There was no sex-related difference. The intake was greater than 1 mg/day in 2 men and 3 women. The daily tin intake was closely related between husbands and wives of 20 couples (r=0.995). Further analysis showed that the consumption of canned foods appeared to be the major source of the increased dietary tin intakes. Conclusions : 1)The use of high purity reagents (with low tin contents) were essential for tin determination. 2)Tin intake of general Japanese population was basically low, i.e.,5.3-5.7 μg/day as a median intake for men and women, respectively. 3)Consumption of canned foods induced a remarkable increase in dietary tin intake.