Volume 5, Number 4, Section 2
The 5th
International Symposium on Clinical Nutrition (4-7 Feb 1996)
VIII.
Application of stable isotope tracers in human nutrition
54. Stable isotope probes of body
protein dynamics in vivo
Dennis M Bier MD
Classical nitrogen balance approaches to quantifying
body protein status provide important and often crucial information
on overall net gain or loss of body protein stores. Nonetheless, balance
data alone are insufficient for assessing the mechanism(s) leading
to the measured changes in nitrogen balance since many permutations
of the relationships between body protein synthesis and body protein
breakdown can produce the same net change in nitrogen balance. Thus,
in order to provide a full picture of the pathophysiological events,
it is necessary to quantify the dynamics of body protein synthesis
and breakdown in vivo. Since these events occur intracellularly, that
is within body compartments inaccessible to sampling by conventional
means, it is necessary to trace the processes taking place within
these compartments with probes that enter the cell, participate in
the protein kinetic events of interest, and return to the accessible
plasma compartment where the results of their journey are recorded
by appropriately timed sampling algorithms. Stable isotopically, labelled
amino acid tracers are absolutely safe probes of this kind and this
lecture will focus on the expanded information one can gain during
in vivo studies of protein metabolism using such tracers. Specifically,
examples of both simple and comprehensive modeling approaches to body
protein kinetics will be presented. The assumptions, advantages, and
limitations of each level of approach will be discussed.
55. Use of stable isotopes to study
mineral absorption in children
Lifschitz CH, Abrams SA
In classical balance studies, the net absorption of
a nutrient is calculated by measuring the difference between mineral
input from the diet and total faecal mineral output. This methodology
does not provide accurate information on absorption, as cumbersome
faecal collections are subject to many errors, and the results are
a combination of unabsorbed minerals and minerals secreted into the
gut lumen. Stable, nonradioactive isotopes offer a safe alternative
approach with accurate results. Ca and Zn studies utilise the dual-tracer
technique: one isotope is administered intravenously and another one
orally, followed by a urine collection. The relative fraction of the
oral versus the intravenous tracer dose represents the fraction of
the oral tracer dose that was absorbed. In Fe studies, the incorporation
into red blood cells of an orally administered isotope of Fe is measured
2 weeks after ingestion. The methodology has been used to study Ca
absorption in preterm and term infants and, patients with juvenile
rheumatoid arthritis, as well as Ca and Fe absorption from weaning
foods. Examples of our own and other investigators work will be presented.
IX. Age-related nutritional problems
Tienboon P
Adolescents are commonly thought to be a generally
healthy population. In fact, a number of specific nutritional problems
exist during this crucial period of human life. The World Health Organization
considers ages 10-19 years as adolescence; the term 'young people'
refers in general to the age range 10-24 years. Early adolescence
is defined as 10-14 years, middle adolescence as 14-17 years, and
late adolescence as 17-20 years. It has been shown that of all age
groups, adolescents had the highest prevalence of 'unsatisfactory'
nutritional status. Adolescents tended to consume less than the RDA
of calcium, iron, vitamin A & C. Food habits of adolescents are
characterised by (1) a tendency to skip meals (especially breakfast
& lunch); (2) snacking; (3) inappropriate consumption of fast
foods; (4) dieting. Some adolescents are dissatisfied with their body
image, search for self-identify, desire for peer acceptance, and adopting
the adolescent lifestyle. In Australia, adolescent boys start drinking
alcohol on average at 12.4 years (Thailand; 13.5 years) whereas girls
started a little later (Thailand; 13.7 years). About 45% of Australian
adolescents aged 14-15 years stated that they currently consumed alcohol;
only 8% of Thai adolescents reported this. Approximately 20% of adolescents
in Australia and from Thai well-to-do families are overweight or obese.
Only 5% of Thai adolescents from low socioeconomic families are overweight
or obese. In developed countries such as Australia, the prevalence
of blood total cholesterol levels above 4.5mmol/L (170mg/dL) in adolescents
aged 14-15 years are 23% for boys (Thailand: 21%) and 40% for girls
(Thailand: 50%). In Thailand, adolescents aged 13-16 years from high
socioeconomic families were taller (boys 7cm; girls 5cm) and heavier
(boys 7kg; girls 5kg) than adolescents from low socioeconomic families.
Hautvast, Joseph GAJ, van Staveren, Wija A, de
Groot, Lisette CPGM
In this report two issues will be discussed. In the
first place a short report is given about a large European nutritional
health study in elderly called SENECA (Survey in Europe on Nutrition
and the Elderly, a Concerted Action). In the second place we will
discuss future research needs and opportunities with regard to nutrition
and health in the elderly.
SENECA: The aim of this study was to explore
nutritional health and performance of older adults age 70-75 years
at baseline and changes over a period of 5 years. Both overnutrition
and undernutrition was found in higher percentages than in adults.
The nutrient supply and biochemical indices report low vitamin B6,
B12 and D status. Socio-economic aspects were found to play an important
role in providing an adequate nutrient supply. Some changes over a
period of 5 years will be discussed.
Future research: Future research in elderly
should not be limited towards interest in when and how people die,
but also in the quality of their survival. It will be a great challenge
to study in depth the role of food and nutrition contributing to the
quality of this survival. We thereby have to be aware that elderly
should not be studied as a homogeneous group and therefor different
subgroups should be identified.
58. Dietary trace elements and nutritional
status of the elderly people in Padang area, west Sumatra, Indonesia
Oenzil F, Itoh Y, Agus Z, Bakhtiar H, Lipoeto I,
Nakano, M
The aim of this study was to clarify the dietary food
habits and nutritional status of elderly people (>60 years old),
residents in Padang city and suburbs. The 24-hr food recall was used.
Artificial food models were used for estimating the portion size.
Most respondents (86%) were below 2000kcal in daily energy intake,
and this low energy intake was reflected in their low body mass index
(BMI). For daily intake of total protein, 87% of respondents were
below 60g/day. The requirement of dietary protein is 60-80g/day, so
protein intake of elderly people in Padang was very low. The main
energy source was carbohydrate. Daily fat intake was also rather low,
33% of the respondents consumed more than 50g/day, and 47% below 30g/day.
In case of carbohydrate, 87% of the respondents were more than 200g/day.
Furthermore, daily intake of iron and calcium was very low: Sixty
percent and 27% of the respondents were below 200mg Ca/day and below
5mg Fe/day, respectively. In order to improve dietary habits and nutritional
status, people in Padang need more dietary protein and trace elements
such as calcium and iron.
59. Nutritional status of rural Malay elderly in Kelantan, Malaysia
Wan A Manan, Abdul Manaf Hj Hamid, Kamaruzaman
Wan Su, Hasenan Nordin
A study was carried out in rural Kelantan villages
to assess the nutritional situation and health status of active, free
living Malay elderly population (age 60-85 years old). A total of
135 respondents (N=135) participated in the study. Dietary intake,
body mass index, disease prevalence (clinical examination) and haemoglobin
levels were recorded. The results were as follows: 60.2% suffered
from chronic energy deficiency, 50.4% were anaemic and 42.2% had chronic
diseases. Dietary findings show that 97.0% had insufficient total
energy intake, 91.9% low in protein intake, 91.8% low in vitamin intake
and 94.9% had low iron intake. It can be concluded that the prevalence
of chronic undernutrition or subclinical malnutrition among elderly
people in Kelantan is significantly high. Thus in general their nutrition
and health status is not satisfactory.
60. Breastfeeding initiatives after
delivery
Wan A Manan, Yasmin Anum MY, Shirley Yeoh YS, Letchumi
M
A total of 100 mothers (N=100) were observed and interviewed
after delivery in the Hospital Universiti Sains Malaysia wards to
assess the initiation of breastfeeding. All respondents were interviewed
between 2 and 29 hours after delivery, where more that half (54%)
were interviewed in less than 12 hours after delivery. Of the mothers,
33% were primipara. The time taken from delivery till the first act
of breastfeeding ranges from 1 to 7 hours for 92% of the mothers.
61% of the mothers breastfed their previous babies, where 80% said
they did for more than 1 year. The frequency of feeding since delivery
and the time of the interview show that more than 95% breastfed 1-5
times. The duration of feeding was between 5-20 minutes in 92% of
the mothers. About 20% of the breastfeeding mothers discarded their
colostrum during their first feeding; among the reasons given were
that the colostrum is dirty and it is a form of traditional practice.
The study also sought opinions of mothers on the benefits of breastfeeding
and infant formula. The decision to breastfeed was based on the information
the mothers received from various sources and encouragement from several
parties.
61. Infant feeding practices in Kelantan,
Malaysia
Wan A Manan, Norzaini Rose MZ, Daw Win Kyi
A total of 65 mothers (N=65) were interviewed using
a prepared questionnaire on the feeding practice of their children
whose age 24 months and below. The respondents were selected by employing
a systematic sampling method on those mothers who attended the Child
Health Clinics in Hospital Universiti Sains Malaysia, Kota Bharu and
Tumpat. Most of the interviews were conducted in the home of respondents.
The results indicated that 41.5% of the respondents exclusively breastfeed
their children ranging from 2 to 12 months duration, while 55.4% practised
mixed feeding, and 3.1% bottle fed their baby exclusively. Reasons
for stopping of breastfeeding were also recorded. The age of weaning
for babies varies from 2 to 8 months. The introduction of the adult
diet was started between the age of 7 and 24 months. Most of the mother
(86.2%) were aware of the complications that can arise due to improper
weaning practices, where diarrhoea and vomiting were commonly cited.
Among the foods believed to increase breast milk production during
the lactation period are powdered milk, protein food, fruits and vegetables
and drinks. A significant number of respondents believed in the concept
of "cold" food (41.5%), "hot" food (20%) and "windy"
food (46.2%).
X. Perspective of nutrients, non-nutrients, and health
62. Vitamin A: from gene expression
to clinical studies
Chytil F
In the last decade methods of molecular biology have
facilitated exploration of molecular mechanisms involved in action
of retinol (vitamin A) and its derivatives, retinoids, with an unprecedented
interest. A wealth of evidence points to the cell nucleus as a target
for their action in influencing expression of quite a few genes. In
addition, the family of natural retinoids originally composed from
retinol, retinal, all-trans- and 13-cis-retinoic acid was enlarged
by discoveries of other metabolites of retinol including 14-hydroxy-retro-retinol,
9-cis, 9,13-dicis-, 4-hydroxy-, 4-oxo-, 18-hydroxy- and 3,4-didehydroretinoic
acid. Major efforts have been directed toward elucidation of how retinoids
(in most instances retinoic acid appears to be the most potent retinoid)
are involved in the time dependent activation and repression of specific
gene products linked to their role in cellular differentiation, organogenesis,
perinatal development, organ maturation and even morphogenesis. Interaction
of retinoic acid with the genome involves two families of unclear
retinoic acid receptors (RAR and RXR). These proteins act as homo-
or heterodimers with respective response elements on DNA.
Parallel to this research, retinoids were successfully
used in the therapy of skin hyperkeratoses, measles and bronchopulmonary
dysplasia of prematurely born human neonates. Safety aspects of administration
of retinoids have been defined. Most dramatic beneficial effects were
seen when high doses of all-trans-retinoic acid were introduced as
treatment of promyelocytic leukemia, which is characterised by chromosomal
translocation of one position of a nuclear retinoic acid receptor
[supported in part by USPHS grant HL 14214].
63. Carnitine-choline interactions:
a perspective on human health
Sachan Dileep S, Dodson Wanda L, Daily, James W
Nutrient-nutrient interactions, without a deficiency
of one, are poorly characterised for most conditionally essential
nutrients such as choline and carnitine. We have discovered an interaction
between these two nutrients that has the potential to profoundly affect
human nutritional requirements for both nutrients. We have demonstrated
a conservation (65%) of carnitine as a result of moderate increase
(20mg/kg/day) in dietary choline in otherwise choline sufficient humans.
This effect of choline was consistently present regardless of ethnicity
and food habits of free-living individuals. We have established an
animal model (guinea pig) which responds to choline-induced carnitine
conservation akin to humans and allows further understanding of the
interaction at organ and cellular level which is too invasive to be
practical in humans. Choline supplemented diet increased concentrations
of carnitine in all organs especially in skeletal muscle where it
is proposed to increase fat utilisation for energy. Choline-mediated
altered tissue partitioning of carnitine has significant implications
for nutrient requirement in normal healthy individuals.
64. Zinc and copper status in thalassemic
children
Tanphaichitr VS, Visuthi B, Tanphaichitr V
Plasma zinc, erythrocyte zinc, urinary zinc, plasma
copper, and erythrocyte superoxide dismutase (SOD) were measured in
10 healthy children and 47 thalassemic children consisting of 11 children
with HbH disease, 26 children with b-thalassemia /HbE disease, and
10 children with b-thalassemia major. Their age ranged from 4 to 15
yrs. All of the results shown below are presented as means±SD. The
significantly lower plasma and erythrocyte zinc levels but significantly
higher urinary zinc level in thalassemic children than those in healthy
children indicate their inadequate zinc status caused by hyperzincuria
which is most likely due to the release of zinc from haemolysed red
blood cells (RBC) evidenced by the significantly negative correlation
between their urinary and erythrocyte zinc levels (r=-0.70, p<0.001).
The significant increases in plasma copper level and plasma Cu:Zn
ratio are consistent with zinc deficiency whereas their significantly
high erythrocyte SOD activity is at least in part due to increased
plasma copper level supported by the significantly positive correlation
between plasma copper level and erythrocyte SOD activity (r=0.46,
p<0.001). Our findings of significantly positive correlations between
plasma zinc levels and height-for-age (r=0.26, p<0.05), mid upper
arm circumference (r=0.41, p<0.005), and upper arm muscle circumference
(r=0.41, p<0.005) also indicate that zinc deficiency is another
factor affecting growth of thalassemic children.
| Children |
Plasma Zn
|
RBC Zn |
Urine Zn |
Plasma Cu
|
Plasma Cu:Zn
|
RBC SOD
|
| |
mg/dL |
mg/g/Hb |
mg/d |
mg/dL |
|
mg/g/Hb |
| Healthy |
118±12 |
91±9 |
322±59 |
104±16 |
0.89±0.14 |
3577±329 |
| Thalassemia |
102±16b |
71±14a |
611±170a |
126±32a |
1.25±0.42a |
5750±1350a |
Significant difference from healthy children: a
p< 0 001, b p<0. 005
Copyright © 1996 [Asia Pacific Journal of Clinical
Nutrition]. All rights reserved.
Revised:
January 19, 1999
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