Original Article
Prevalence of thiamin and riboflavin deficiency among
the elderly in Taiwan
Feili Lo Yang
PhD,1Pei-Chun Liao
MS,1Yung-Ying Chen
MS,1Jui-Line Wang
PhD,2and Ning-Sing Shaw
PhD2
1 Fu Jen Catholic University, College of Human Ecology, Department of Nutrition and Food Sciences,
Sinjhuang, Taiwan
2 National Taiwan University, Institute of Microbiology and Biochemistry, Department of Biochemical
Science and Technology
The purpose of this study was to perform biochemical assessments of the nutritional status of thiamin and riboflavin in the 2379 elderly persons (1213 males, 1166 females) participating in the Elderly Nutrition and Health Survey in Taiwan (1999-2000) (Elderly NAHSIT). Through analysis of the data we aimed to investigate possible factors related to the prevalence of vitamin deficiency. Activity coefficients of erythrocyte transketolase and glutathione reductase (ETKAC and EGRAC) were the chosen biochemical indicators for thiamin and riboflavin status. The results showed that 14.7% of men and 11.9% of women were marginally thiamin deficient, and 16.5% of men and 14% of women were thiamin deficient. The prevalence rates of marginal riboflavin deficiency were 25.7% for males and 20.1% for females, and the deficiency rates were 6.6% for elderly males and 4.1% for elderly females. Although the average dietary thiamin and riboflavin intakes reached 146% - 164% of Taiwan RDAs, the percentage of senior citizens whose thiamin or riboflavin dietary intakes were less than EARs (equivalent to 83.3% of RDAs) was around 30% for males and 40% for females. Some contributing factors to the significant prevalence of thiamin and riboflavin deficiencies are discussed in this article.
Key Words: thiamin status, riboflavin status, elderly, nutritional assessment, Taiwan, Elderly Nutrition and Health Survey in Taiwan (1999-2000)
Introduction
Thiamin and riboflavin are important coenzymes in fuel metabolism. Thiamin, in the coenzyme form of thiamin pyrophosphate (TPP), participates in the oxidative decar-boxylation of α-ketoacids and the transketolation between hexoses and phosphopentose in the hexose monophosphate shunt.1,2 Because of these biochemical functions, thiamin
assists in the metabolism of carbohydrate and branched-chain amino acids as well as in the generation of ribose required for nucleic acid synthesis and NADPH required for fatty acid synthesis.1,2 In addition, thiamin may also
play a significant role in neurotransmitter functions and nerve conduction.2 Riboflavin, in the coenzyme forms of
flavin mononucleotide (FMN) and flavin adenine dinucleo-tide (FAD), catalyzes numerous oxidation-reduction re-actions in intermediary metabolism.3,4 Riboflavin also
functions in the metabolism of drugs, steroids, and lipids.3,4
Erythrocyte transketolase (ETK, EC 2.2.1.1) and ery-throcyte glutathione reductase (EGR, EC 1.6.4.2) are the TPP and FAD dependent enzymes in red blood cells re-spectively. Deficiency of thiamin or riboflavin results in desaturation of the respective cofactors of the two de-pendent enzymes. Determining the activity coefficient by measuring the stimulatory effect of in vitro addition of TPP or FAD to erythrocyte specimens allows the assessment of
the long-term biochemical status of thiamin and ribo-flavin.5,6
Among the previous nationwide nutritional surveys, the Nutrition and Health Survey in Taiwan 1993-1996 (NAHSIT 1993-1996) was the first to use biochemical indices such as ETKAC and EGRAC together with dietary assessment and anthropometric measurements to assess the nutritional status of thiamin and riboflavin for Taiwanese aged 4 years and above.7.8
The NAHSIT 1993-1996 surveyed only 213 male and 194 female elderly people. The results of the survey in regards to the elderly (≥65 yrs) showed that the marginal and deficient rates of thiamin for males were 19.9% and 10.9%, and the rates for females were 9.8% and 10%, re-spectively.7 The status of riboflavin was markedly worse
with marginal and deficient rates of 35.6% and 43.7% for elderly men, and rates of 38.7% and 33.4% for elderly elderly women, respectively.8 In order to continue to
mo-nitor the nutritional status of Taiwanese citizens with a Correspondence address: Feili Lo Yang, 510 Jongjeng Road,
Sinjhuang, Taipei Hsein, Taiwan 24205 Tel: +886-2-29053611; Fax: +886-2-29021215 E-mail: nutr1015@mails.fju.edu.tw
particular emphasis on the elderly, which is a rapidly in-creasing population, the Elderly Nutrition and Health Survey in Taiwan (1999-2000) (Elderly NAHSIT) was carried out in 1999-2000. The purpose of this article is to report the results of thiamin and riboflavin status of Taiwanese seniors found in this most recent survey and to discuss possible contributing factors to the current situ-ation.
Materials and methods Study design
This survey adopted a multi-staged, stratified, clustered probability sampling scheme. The rationale and details of the study design and sampling procedures have been described in a separated article by Pan et al.,9 in this
issue. Taiwanese residents of 65 years old and over were the target population.
Blood sample preparation
Fasting venous blood samples were collected into he-parinized vacutainers (Becton Division). Plasma was immediately separated in the field by centrifugation at 4˚C. After removal of plasma samples, packed erythro-cytes were removed from the bottom of the centrifuge tubes and transferred to individual 2.0ml polypropylene cyrovials which were immersed into liquid nitrogen immediately. The erythrocyte specimens were kept and shipped on dry ice within 24 hours and then frozen at -80°C until analysis. To monitor the reproducibility of laboratory analyses, 5% split samples were prepared and blind-coded in the field as well. A total of 2,379 erythro-cyte specimens (1,213 for men, 1,166 for women) were analyzed.
ETKAC and EGRAC analysis
ETKAC and EGRAC were the biochemical indices se-lected to evaluate the long term nutritional status of thia-min and riboflavin. The activity coefficient was deter-mined by a ratio of respective enzyme activity stimula-ted with an added cofactor (TPP or FAD) to that without an added cofactor. The protocol of Mount et al.,10 was
employed to determine the ETKAC and EGRAC, and
the semiautomatic analytical procedures were standar-dized to conduct the analyses on Cobas Fara II (Roche). The cut-off points for judging thiamin status were an ETKAC <1.15 for normal thiamin status, 1.15 ≤ ETKAC <1.20 for marginal deficient thiamin status, and ETKAC ≥1.20 for thiamin deficiency.5,10 The cut-off points for
determining riboflavin status were an EGRAC 1.20 for normal riboflavin status, 1.20 ≤ EGRA <1.40 for marginal deficient riboflavin status, and EGRAC ≥1.40 for ribo-flavin deficiency.6,10
Dietary thiamin and riboflavin intake
Dietary intake information was collected by trained sur-veyors using 24-hour recall. The dietary nutrient contents of subjects’ diets, including thiamin and riboflavin, were calculated mainly by using the “Food nutrient content data base of Taiwan” and many other nutrient databases. The details of dietary nutrient intake data collection and calculation are described by Wu et al. in this issue.11 Of
all the 24-hour recalls collected, 955 men and 957 women had complete information. Therefore, only they were used for the analysis of dietary thiamin and riboflavin intakes. Statistical analysis
Data were weighted for the unequal probability of sam-pling and analyzed by SAS for PC 8.0 and SUDAAN software in order to extrapolate the results to the whole elderly population in Taiwan. Two-way ANOVA was used for the comparison of ETKAC and EGRAC by age and sex. The details of the rationale and procedures of SUDAAN are reported by Pan et al.,9 in this issue.
Results
The theoretical sample size of the Elderly NAHSIT was to include 2028 aged men and women, however, in actua-lity a total of 2504 participants provided blood specimens. After deletion of the disqualified or deteriorated samples, data on the ETKAC and EGRAC from 2,379 blood spe-cimens (1,213 males, 1,166 females) were analyzed. With the standardization of assay procedures, the analysis of split samples showed a percentage of variation (%CV) of less than 5% for both ETKAC and EGRAC.
Table 1. Prevalence of thiamin and riboflavin deficiencies in elderly Taiwanese by age and sex 1
Sex Thiamin status3 Riboflavin status4
Age(yr) N ETKAC2 Normal Marginal Deficient EGRAC2 Normal Marginal Deficient
Male % % 65-69 453 1.11 ± 0.01 66.5 15.2 18.3 1.17 ± 0.01 63.0 29.9 7.1 70-74 423 1.09 ± 0.01 69.6 15.6 14.8 1.16 ± 0.01 70.5 22.6 6.9 75-79 222 1.10 ± 0.01 70.6 13.6 15.6 1.16 ± 0.01 70.0 25.3 4.7 ≥ 80 115 1.10 ± 0.02 70.0 13.1 17.0 1.17 ± 0.02 70.2 22.3 7.4 Total 1213 1.10 ± 0.01 68.8 14.7 16.5 1.17 ± 0.01 67.7 25.7 6.6 Female 65-69 476 1.09 ± 0.01 75.6 11.4 13.1 1.13 ± 0.01 79.1 17.6 3.3 70-74 355 1.08 ± 0.01 74.8 11.3 13.9 1.14 ± 0.01 76.0 21.7 2.3 75-79 213 1.10 ± 0.01 73.0 12.8 14.2 1.15 ± 0.01 72.7 22.4 4.8 ≥ 80 122 1.10 ± 0.01 70.8 13.3 16.0 1.16 ± 0.02 71.6 20.5 7.9 Total 1166 1.09 ± 0.01 74.1 11.9 14.0 1.14 ± 0.01 75.8 20.1 4.1
1Data were weighted for unequal probability of sampling and analyzed by SUDAAN software; 2Means ± SE analyzed by two-way ANOVA; 3Cutoff points of thiamin status are ETKAC 1.15 for normal status, 1.15 ≤ ETKAC < 1.20 for marginal status, and ETKAC ≥1.20 for deficient
status; 4Cutoff points of riboflavin status are EGRAC <1.20 for normal status, 1.20 ≤ EGRAC <1.40 for marginal status, and EGRAC ≥1.40
The results for ETKAC and EGRAC across the va-rious age groups of elderly men and women were within the normal range and were not significantly different either between age groups or between males and females. However, 14.7% of elderly men and 11.9% of elderly women had marginal thiamin status, and 16.5% of elderly men and 14.0% of elderly women had deficient thiamin status (Table 1). In addition, according to EGRAC re-sults, 25.7% of men and 20.1% of women were classi-fied as having marginal riboflavin status, and 6.6% of men and 4.1% of women surveyed were classified as be-ing riboflavin deficient (Table 1). The average dietary thiamin and riboflavin intakes of elderly men and women did not differ significantly across the various age groups (Table 2). When compared with Taiwan RDAs (Recom-mended Dietary Allowances) of thiamin and riboflavin for respective sex and age groups, the mean thiamin and riboflavin intakes met the Taiwan RDAs for all age groups and both sexes (Table 2).
The results of the dietary thiamin and riboflavin in-takes expressed as distributions of selected percentiles are shown in Table 3. Intakes were compared with the RDAs for males and females over 71 years old with light levels of physical activity. The range of intakes of both thiamin and riboflavin and the percentage of Taiwanese RDA (%RDA) consumed was quite large between the 5th and
the 95th percentiles. The median dietary thiamin intake
for both elderly men and women was very close to the RDAs, whereas the median dietary riboflavin intakes were lower than the RDAs for both elderly men and women.
Discussion
Around half of a century ago, thiamin and riboflavin defi-ciencies were among the most serious malnutrition problems in Taiwan. In the nutrition status survey of the civilian population in Taiwan conducted in 1954, absent ankle jerks, a sign of thiamin deficiency, was present in only 2 - 5.6% of college students and adults. However
the prevalence of low excretion of urinary thiamin (less than 50 µg/g creatinine) was as high as 55.4% in the sur-veyed sixth grade school children, indicating high preva-lence of low thiamin intake.12 The incidence of active
angular stomatitis, a clinical sign of riboflavin deficiency, was as high as 39 - 86% in all age groups of six years old and over.12-14 The inadequate thiamin intake was related
to improper rice milling processes, whereas low ribo-flavin intake was due to lack of food sources providing significant amounts of this vitamin.13 In 1972, another
nutrition status survey of the civilian Taiwanese popu-lation showed remarkable improvement in thiamin and riboflavin status.15 However, the incidences of low
uri-nary thiamin and riboflavin excretion was 9.3% and 33.7% respectively in sixth grade children, and the pre-valence of active angular stomatitis was still as high as 17.5% in this age group.15
Although severe deficiencies of thiamin and riboflavin have been rarely seen, the presence of a substantial per-centage of elderly people with low or marginal thiamin and riboflavin status has been a persistent but overlooked nutritional problem in Taiwan. The elderly persons sur-veyed in the NAHSIT 1993-1996 (the 1993-1996 study) were equivalent to the 70 years and older age group in the Elderly NAHSIT (the 1999-2000 study). The current survey of the elderly also reported similar rates of defi-cient and marginal thiamin status. Comparing the thiamin insufficiency rates in these two consecutive NAHSITs,7
there is no indication that the thiamin status of the Tai-wanese elderly has improved over the past few years. The riboflavin status of elderly people, however, showed significant progress in the 1999-2000 study. The rates of marginal deficiency in the elderly population de-creased from 34.6% in males and 38.7% in females in the 1993-1996 study8 to 25.7% in elderly males and 20.1% in
females in the current survey. The prevalence of ribo-flavin deficiency also greatly decreased from 43.7% in elderly males and 33.4% in females in the 1993-1996 study8 to 6.6% in males and 4.1% in females in the
1999-2000 study. However, individuals with marginal or defi-cient status still accounted for one third of the male and one fourth of the female senior residents who need further improvement in their long term thiamin and riboflavin status.
The dietary thiamin and riboflavin intakes of elderly men and women from various age groups all met the RDAs established by the Department of Health in Tai-wan. Although the dietary nutrient intake obtained by 24-hour recall may not fully reflect the long term dietary pattern of individual subjects, the percentile distribution of dietary nutrient intakes constructed from nearly one thousand items of data may still allow us to gain an over-view regarding the dietary nutrient intake of the surveyed population. The median (50th percentile) dietary thiamin
intake was 0.92 mg/day in males and 0.72 mg/day in females. This is 26% and 29% lower respectively, than the average intakes of thiamin by men and women, which reached 100% of the RDAs. Since the RDAs of thiamin and riboflavin are defined as being equal to their corre-sponding EARs (estimated average requirements) plus twice the coefficient of variance (assuming 10%) to cover Table 2. Comparison of dietary thiamin and riboflavin
intakes1 of the elderly with Taiwanese RDAs2 by age
and sex
Sex Thiamin Riboflavin
Age
(yr) N Intake % RDA Intake % RDA
Male (mg/day) (%) (mg/day) (%)
65-69 356 1.12 ± 0.06 124 1.29 ± 0.10 129 70-74 326 1.30 ± 0.01 163 1.53 ± 0.09 170 75-79 186 1.23 ± 0.13 154 1.51 ± 0.13 168 ≥ 80 87 1.36 ± 0.17 170 1.37 ± 0.19 152 Total 955 1.25 ± 0.07 156 1.42 ± 0.08 158 Female 65-69 392 0.99 ± 0.07 124 1.28 ± 0.10 160 70-74 302 0.97 ± 0.06 139 1.37 ± 0.08 171 75-79 154 1.25 ± 0.20 179 1.31 ± 0.13 164 ≥ 80 109 0.91 ± 0.09 130 1.26 ± 0.13 158 Total 957 1.02 ± 0.06 146 1.31 ± 0.06 164
1Values are means ± SE analyzed by SUDAAN software; 2 Taiwanese
RDAs of thiamin and riboflavin for elderly people with a low level of physical activity were used as the reference: thiamin RDAs for the elderly ≤70 yrs: 0.9 mg/day for males and 0.8 mg/day for females; thiamin RDAs for the elderly ≥71 yrs: 0.8 mg/day for males and 0.7 mg/day for females; riboflavin RDAs for the elderly ≤70 yrs: 1.0 mg/day for males and 0.8 mg/day for females; riboflavin RDAs for the elderly ≥71 yrs: 0.9 mg/day for males and 0.8 mg/day for females
the needs of 97.5% of the population in a certain age
group, EARs are equivalent to 83.3% of RDAs. The die-tary thiamin intake of males and females ranked below the 30th percentile were less than the Taiwan EARs for
thiamin (83.3% of RDAs). The median intake of dietary riboflavin was 0.98 mg/day for elderly males and 0.90 mg/day for females, both of which are slightly higher than 100% of the RDAs. The dietary riboflavin intake of elderly men and women who ranked below the 40th
per-centile was lower than the EARs. In contrast, the dietary thiamin and riboflavin intakes of elderly people who ranked at the higher ends of the percentile distribution were 3.3 to more than four-fold of the RDAs. Therefore, the average nutrient intakes were affected by this skewed distribution of nutrient intake and may not be able to reflect the presence of nutrient intakes far below the RDAs within the population. If evidence of a consider-able portion of the population having inadequate thiamin and riboflavin intake persists, the consequential deteriora-tion of the nutrideteriora-tional status of these water-soluble vita-mins could continue in the future.
Nutritional status is greatly influenced by the dietary patterns and food preferences of a population. According to the analyses of dietary data by Wu et al.,11 the major
food source of thiamin for the elderly was pork and its products, which provided 0.38 mg/day (33.3% of average intake) of thiamin; followed by rice and its products (0.16 mg/day, 14% of total intake); dairy products (0.09 mg/ day, 7.9% of total intake); wheat and flour products (0.08 mg/day, 7.0% of total); and soy beans and soy products (0.08 mg/day, 7.0% of total).11 The remaining food
cate-gories only provided a limited amount of thiamin (less than 0.05 mg/day) to the diet of elderly people.11 Staple
foods including polished rice, wheat flour, and tubers and their products provided 0.27mg (23.7%) of dietary thia-min. Compared with the results regarding dietary thiamin sources of adults in the NAHSIT 1993-1996,16 the patterns
and percentage of dietary food sources were very similar
in the two consecutive NAHSIT studies. Therefore, it seems that deriving almost 50% of dietary thiamin from very scattered food sources with low thiamin content has been a long term problem in the dietary patterns of the elderly. This may be one of the underlying factors which have contributed to the high percentage of the elderly population with inadequate dietary thiamin intakes and unsatisfactory biochemical status. Since the protein intake of the elderly already meets the recommended amount,11
it may not be appropriate to suggest that the elderly consume more animal protein to gain more dietary thia-min. Instead, replacing portions of polished rice and pro-ducts with whole grains as a staple food would greatly en-hance the thiamin content of the diet, especially for those with insufficient intakes.
The major food source of riboflavin for the elderly re-ported by Wu et al., was dairy products,11 which provided
0.52 mg/day of dietary riboflavin (equivalent to 38.5% of the average daily intake) to the elderly population. The food categories that were the next highest sources of ribo-flavin intake were pork and its products (0.12 mg/day, 8.9% of total intake), wheat and its products (0.11 mg/ day, 8.1% of total intake), fresh fruits (0.1 mg/day, 7.4% of total diet), dark green vegetables (0.08 mg/day, 5.9% of total intake), and eggs and their products (0.07 mg/day, 5.2% of total). The remaining food categories each pro-vided less than 3% of dietary riboflavin.11 This pattern of
dietary riboflavin intake is also very similar to the fin-dings in the NAHSIT 1993-1996.16 Traditionally, dairy
products have not been a major food category consumed by Taiwanese adults. Probably because of the awareness of dairy consumption for the prevention of osteoporosis and the increase in popularity of dairy foods, the average consumption of dairy products has gradually increased from 0.3 cups by adult males and 0.4 cups by adult fe-males in the 1993-1996 study17 to 0.8 cups by elderly men
and 0.9 cups by elderly women in the 1999-2000 study.11
The increase in dairy product consumption may be the Table 3. Distributions of selected percentiles of dietary thiamin and riboflavin intakes1 of the Taiwanese elderly
population
Thiamin Riboflavin
Percentile Male Female Male Female
Intake % RDA2 Intake % RDA2 Intake % RDA2 Intake % RDA2
5th 0.28 35 0.21 30 0.23 26 0.17 21 10th 0.36 45 0.28 40 0.32 36 0.23 29 15th 0.44 55 0.33 47 0.41 46 0.32 40 25th 0.59 74 0.43 61 0.56 62 0.44 55 30th 0.65 81 0.49 70 0.63 70 0.51 64 40th 0.77 96 0.60 86 0.76 84 0.68 76 50th 0.92 115 0.72 103 0.98 109 0.90 113 60th 1.00 125 0.80 114 1.24 138 1.14 143 75th 1.46 183 1.18 169 1.82 202 0.66 208 85th 1.91 239 1.59 227 2.37 263 2.26 283 90th 2.34 293 1.92 274 3.03 337 2.85 356 95th 3.31 414 2.73 390 3.85 428 3.72 465
1Data on dietary intakes of nutrients were obtained for the results of the 24-hour recall; 2Taiwanese RDAs for thiamin and riboflavin
cause of the great reduction in riboflavin deficiency that has been observed in the 1999-2000 study. Without a nu-trient fortification policy, staple foods currently provide only very limited amounts (0.16 mg/day, 11.8% of total intake) of riboflavin in the diet of the elderly. In the First Nationwide Nutrition Survey held during 1980-1981, organ meat was the third major contributor of dietary riboflavin which provided 9.2% (0.10 mg/day) of the mean daily intake.18 However, following concern about
the cholesterol content and safety of organ meat, it has disappeared from the list of major food sources.
It seems that the policy of nutrient fortification in staple foods practiced by the United States guarantees a sufficient dietary intake of thiamin and riboflavin for the majority of the population.19,20 According to the results of
the Continuing Survey of Food Intakes by Individuals (CSFII) 1994-1995, food groups containing mainly forti-fied staple foods, such as bread and bread products, mixed foods with grain as a main ingredient, ready-to-eat cereal, pasta, rice and cooked cereal, provided about 44% of total dietary thiamin and 30% of dietary riboflavin for US adults.19,20 Therefore, both the CSFII 1994-1995 and the
NHANES III 1988-1994 showed quite agreeable results that the mean dietary thiamin and riboflavin intakes of the 5th percentile of elderly males already meet the EARs and
those of the 5th-25th percentile of elderly females also
meet the EARs set by the US Institute of Medicine.19,20
Without a nutrient fortification policy, dietary supple-ment use may be another choice to eliminate nutrient in-sufficiency. Around 30% of elderly males and 35% of el-derly females use dietary supplements in Taiwan.21 Of
those who use supplements, only about 28% of men and 25% of women choose supplements containing thiamin and/or riboflavin.21 In addition, dietary supplement use
was reported to be highly correlated with urbanization, high degree of education, high monthly income, better awareness of nutrition related information, and being more health conscious.21 These phenomena may partially
explain the great discrepancy in dietary thiamin and ribo-flavin intakes between the means of the 95th and the 5th
percentiles and the skewed distribution of the biochemical status of thiamin and riboflavin in the Taiwanese elderly population.
In addition to the prevention of vitamin deficiency, thiamin status is correlated with the cognitive function of the elderly.22 A sufficient serum level of thiamin is
re-quired for the proper transport of TPP into the mito-chondria of nerve cells23 to ensure normal metabolism of
glucose and neurotransmitters.24 Riboflavin deficiency
not only interferes with intermediary metabolism but also that of pyridoxine, folate and vitamin B12. In an Asian
population such as Taiwan where polished rice is the pre-ferred staple food, dairy products are not customarily con-sumed by the elderly, and no nutrient fortification policy is in place, deficiency of thiamin or riboflavin may occur unless meals are well planned with wise choices of food rich in thiamin and riboflavin.
In conclusion, our study demonstrated the high pre-valence of thiamin and riboflavin deficiency among elder-ly Taiwanese. Although the average biochemical indices and dietary intakes of thiamin and riboflavin were within the normal range, more than one third of the elderly had a
dietary intake of thiamin or riboflavin less than the re-spective EARs. Nutritional intervention in the future is recommended to educate the target population regarding proper food choices, meal planning and dietary supple-ment use to correct thiamin and riboflavin deficiencies. Implementation of a food policy such as mandatory nu-trient content labelling and fortification of nunu-trients for staple foods showing a high prevalence of deficiencies in-cluding thiamin and riboflavin should also be considered. Acknowledgement
We would like to express our appreciation to Dr. J. T. Kao and Dr. S. B. Lin from the Department of Clinical Laboratory and Medical Biotechnology at the National Taiwan University, College of Medicine for kindly providing the Cobas Fara II, which allowed the accomplishment of our laboratory analyses. Sincere appreciation is also extended to Ms. Ya-Hui Chang and Mr. Jen Chen for their assistance in statistical analysis. This study was sponsored by a grant from the Department of Health in Taiwan (DOH90-TD-1100).
References
1. Combs JF Jr. Thiamin. In: The Vitamins. Fundamental aspects in nutrition and health. 2nd ed. San Diego:
Academic Press, 1998:277-294.
2. Tanphaichitr V. Thiamine. In: Rucker RB, Suttie JW, McCormick DB, Machlin LJ, eds. Handbook of vitamins. 3rd ed. New York: Marcel Dekker, 2001;275-316.
3. Combs JF Jr. Riboflavin. In: The Vitamins. Fundamental aspects in nutrition and health. 2nd ed. San Diego:
Academic Press, 1998:295-310.
4. Rivlin RS, Pinto JT. Riboflavin (Vitamin B2). In: Rucker RB, Suttie JW, McCormick DB, Machlin LJ, eds. Handbook of vitamins. 3rd ed. New York: Marcel Dekker,
2001; 255-273.
5. Sauberlich HE. Vitamin B-1 (Thiamin). In: Laboratory tests for the assessment of nutritional status. 2nd ed. Boca
Raton, FL: CRC Press, 1999;37-53.
6. Sauberlich HE. Vitamin B-2 (Riboflavin). In: Laboratory tests for the assessment of nutritional status. 2nd ed. Boca
Raton, FL: CRC Press, 1999;55-69..
7. Pan WH, Kon MJ, Ou-Yang C. Assessment of thiamin biochemical status of residences in Taiwan by erythrocyte transketolase activity coefficient. Taipei: Department of Health, 1998; 173-184. (in Chinese)
8. Pan WH, Kon MJ, Ou-Yang C. Assessment of riboflavin biochemical status of residences in Taiwan by erythrocyte glutathione reductase activity coefficient. Taipei: Depart-ment of Health, 1998; 185-200. (in Chinese)
9. Pan WH,Hung YT, Shaw NS, Lin W, Lee SD, Chiu CF, Lin MC, Chen SY, Hong CM, Huang TY, Chang HY, Tu SH, Chang YH, Yeh WT, Su SC. Elderly Nutrition and Health Survey in Taiwan (1999–2000): research design, methodology and content. Asia Pac J Clin Nutr 2005; 14 (13): 203-210.
10. Mount JN, Heduan E, Herd C, Jupp R, Kearney E, Marsh A. Adaptation of coenzyme stimulation assays for the nutritional assessment of vitamin B1, B2 and B6 using the Cobas Bio centrifugal analyzer. Ann Clin Biochem 1987;24:41-46.
11. Wu SJ, Chang YH, Wei IL, Kao MD, Lin YC, Pan WH. Intake levels and major food sources of energy and nutrients in the Taiwanese elderly. Asia Pac J Clin Nutr 2005; 14: 211-220.
12. Jolliffe N, Tung TC. Nutrition status survey of the civilian population of Formosa. Metabolism 1956;5:309-327.
13. Consolazio CF, Crowley LV, Armstrong FB, Dorsch IF, Guillory RL, Pollack H. Studies on nutrition in the Far East. II. Biochemical findings before and after enrichment of rice with vitamins. Metabolism 1956;5:219-230. 14. Pollack H. Studies on nutrition in the Far East. Studies on
nutrition in the Far East. III. Clinical indicator signs of nutritional insufficiencies before and after enrichment of rice with synthetic vitamins. Metabolism 1956;5:231-244. 15. Huang PC, Lin HT, Tung TC. The change of nutrition
status of the civilian Chinese population of Taiwan in the recent 16 years. J Formos Med Assoc 1972;71:245-255. 16. Wu SJ, Chang YH, Chang HY, Pan WH. Food sources of
dietary vitamin A, vitamin B1, vitamin B2, vitamin C, vitamin E, and niacin: results from a Nutrition and Health Survey in Taiwan (NAHSIT) 1993 ~ 1996. Nutr Sci J 2001; 26:213-228.
17. Wu SJ, Chang YH, Fang CW, Pan WH. Food sources of weight, calories, and three macro-nutrients- NAHSIT 1993 ~ 1996. Nutr Sci J 1999;24:41-58.
18. Pan WH, You SL, Chou J, Huang PC. Major food contributors of various nutrients consumed by Chinese populations in Taiwan, 1980-1981 (II): vitamins and minerals. J Chn Nutr Soc 1991;16:21-37.
19. IOM (Institute of Medicine). Thiamin. In: Dietary reference intakes for thiamin, riboflavin, niacin, vitamin B6, folate,
vitamin B12, pantothenic acid, biotin, and choline.
Washington, DC. National Academy Press 1998;58-86. 20. IOM (Institute of Medicine). Riboflavin. In: Dietary
reference intakes for thiamin, riboflavin, niacin, vitamin B6,
folate, vitamin B12, pantothenic acid, biotin, and choline.
Washington, DC. National Academy Press 1998;87-122. 21. Chen SY, Lin JR, Kao MD, Hang CM. The usage of
dietary supplements among the elderly individuals in Taiwan. Asia Pac J Clin Nutr 2005; 14: 230-237.
22. Ortega RM, Requejo AM, Andres P, Lopez-Sobaler AM, Quintas ME, Redondo MR, Navia B, Rivas T. Dietary intake and cognitive function in a group of elderly people.
Am J Clin Nutr 1997;66:803-809.
23. Tallaksen CM, Bohmer T, Bell H. Concentration of the water-soluble vitamins thiamin, riboflavin, ascor-bic acid and folic acid in serum and cerebrospinal fluid of healthy individuals. Am J Clin Nutr 1992; 56:559-564.
24. Gold M, Chen MF, Johnson K. Plasma and red blood cell thiamin deficiency in patients with dementia of the Alzheimer’s type. Arch Neurol 1995;52:1081-1086.
