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[Antioxidants for prophylaxis of eye
diseases]
Kaluzny J
Klin Oczna (Poland) Feb 1996, 98 (2) p141-3
The contemporary literature has widely described the role
of free oxygen radicals and their antioxidants in pathogenesis
of some eye diseases, mainly cataract, age-related macular
degeneration, retinopathy of prematurity and cystic macular
oedema. This paper presents publications which stress the
importance of antioxidants use in prophylaxis of cataract and
age-related macular degeneration. Positive antioxidants role
was proved both in experimental research and in clinical
observations. (29 Refs.)
Antioxidants and angiogenetic factor associated
with age-related macular degeneration (exudative type)
Ishihara N, Yuzawa M, Tamakoshi A
Department of Ophthalmology, Nihon University School of
Medicine, Tokyo, Japan.
Nippon Ganka Gakkai Zasshi 1997
Mar;101(3):248-51
To confirm the hypothesis that antioxidants and
angiogenetic factors may be associated with the development of
age-related macular degeneration (exudative type), we compared
serum levels of vitamins A, C, and E and carotinoid, zinc,
selenium and b-FGF (basic-fibroblast growth factor) in 35
patients with age-related macular degeneration (exudative
type) with the levels in 66 controls. The average serum zinc
level was significantly lower in the patient group than in the
control group. Serum vitamin E-alpha levels also tended to be
lower. Most serum b-FGF levels were below the standard value
in each group. Based on the above results, we conclude that
subnormal levels of zinc and vitamin E may be associated with
the development of age- related macular degeneration.
Retinal tubulin binds macular carotenoids.
Bernstein PS, Balashov NA, Tsong ED, Rando RR
John A. Moran Eye Center, University of Utah School of
Medicine, Salt Lake City 84132, USA.
Invest Ophthalmol Vis Sci (United States) Jan 1997, 38 (1)
p167-75
PURPOSE: To investigate the biochemical mechanisms
responsible for the specific uptake, concentration, and
stabilization of the carotenoids lutein and zeaxanthin in the
macula.
METHODS: Soluble extracts of bovine retina mixed with
radioactive carotenoids were purified by hydrophobic
interaction, ion exchange, and gel filtration chromatography.
Carotenoid-associated proteins in these purified preparations
were identified through photoaffinity labeling and protein
microsequencing. Similar purifications on human macular tissue
without the addition of exogenous carotenoids also were
performed.
RESULTS: Experiments on bovine retinal tissue demonstrated
that tubulin is the major soluble carotenoid-binding protein.
When soluble extracts of human macular protein were examined,
the endogenous carotenoids lutein and zeaxanthin were
found to copurify with tubulin.
CONCLUSIONS: Tubulin is found in abundance in the receptor
axon layer of the fovea, where it can serve as a locus for the
deposition of the high concentrations of macular carotenoids
found there. The binding interaction of carotenoids and
tubulin in the Henle's fiber layer could play an important
role in the photoprotective effects of the macular carotenoids
against the progression of age-related macular degeneration.
The association of carotenoids with tubulin, a protein that
can form highly ordered linear arrays, may provide an
explanation for the dichroic phenomenon of Haidinger's
brushes.
Cigarette smoking and retinal carotenoids:
implications for age-related macular degeneration.
Hammond BR Jr, Wooten BR, Snodderly DM
Schepens Eye Research Institute, Department of Ophthalmology,
Harvard Medical School, Boston MA 02114, USA.
Rhammond@vision.eri.harvard.edu
Vision Res (England) Sep 1996, 36 (18) p3003-9
The foveal region of the retina has a yellow pigmentation
composed primarily of the carotenoids lutein and zeaxanthin.
Past studies have shown that cigarette smoking depresses
carotenoid concentrations in the blood. This is the first
report on the effects of cigarette smoking on carotenoids in
the retina. Macular pigment optical density (MP) was measured
psychophysically by comparing foveal and parafoveal
sensitivities to light of 460 and 550 nm. General dietary
patterns, smoking frequency (cigaretts/day) and personal data
were collected by questionnaire. Thirty-four smokers and 34
nonsmokers were compared. Subjects were matched with respect
to age, sex, dietary patterns and overall pigmentation (i.e.,
eye, skin and hair color). The smoking group had a mean MP of
0.16 (SD = 0.12) compared to a mean MP of 0.34 (SD = 0.15) for
nonsmokers (P < 0.0001). MP density and smoking frequency
were inversely related (r = -0.498 P < 0.001) in a
dose-response relationship. A variety of evidence suggests
that MP protects the macula from actinic damage both passively
(by screening potentially harmful short-wave light) and
actively as an antioxidant (e.g., by quenching reactive oxygen
species). If smoking causes a reduction in MP density, then
smokers may be at risk. Epidemiologic data identifying smoking
as a risk factor for the neovascular form of age-related
macular degeneration are consistent with this hypothesis.
Sex differences in macular pigment optical density:
relation to plasma carotenoid concentrations and dietary
patterns.
Hammond BR Jr, Curran-Celentano J, Judd S, Fuld K, Krinsky
NI, Wooten BR, Snodderly DM
Schepens Eye Research Institute, Boston, MA 02114, USA.
Vision Res (England) Jul 1996, 36 (13) p2001-12
Sex differences in macular pigment (MP) optical density
(measured psychophysically) were examined. Concentrations of
lutein and zeaxanthin (L and Z) (non-separated) and
beta-carotene (BC) in the blood were determined using reverse
phase high-performance liquid chromatography. Dietary intake
of L and Z, BC, fat, and iron were estimated by questionnaire.
Males had 38% higher MP density than females (P < 0.001)
despite similar plasma carotenoid concentrations and similar
dietary intake (except for fat). Dietary intake of
carotenoids, fat and iron, as well as plasma concentrations of
L and Z were positively related to MP density in males.
Conversely, only plasma L and Z was related to MP density for
females, and dietary fat was negatively related to MP density.
Sex differences in protection of the retina by MP and in the
relationship between the retina, blood and diet could be a
factor in the incidence of retinal diseases, especially
age-related macular degeneration.
Retinol (Vitamin A) supplements in the
elderly
Ward BJ
Centre for the Study of Host Resistance, Montreal General
Hospital, Quebec, Canada
cybj@musica.mcgill.ca
Drugs and Aging (New Zealand), 1996, 9/1 (48-59)
Aging is associated with many changes in epithelial
tissues, immune function and haematopoiesis-myelopoiesis.
There is increasing evidence that retinoids can significantly
influence some of these changes. Retinoids may also have
anticancer effects and protect against age-associated
conditions such as macular degeneration. However, retinol
(vitamin A) can be toxic when taken in excess and the elderly
may be at particular risk for hypervitaminosis A. Evaluation
of elderly people ingesting significantly more or less than
the recommended daily intake of retinol requires an
understanding of the biology of retinoids and consideration of
the relative risks and benefits of supplementation.
Studies on the mechanism of early onset macular
degeneration in cynomolgus monkeys. II. Suppression of
metallothionein synthesis in the retina in oxidative
stress
Nicolas MG, Fujiki K, Murayama K, Suzuki MT, Shindo N, Hotta
Y, Iwata F, Fujimura T, Yoshikawa Y, Cho F, Kanai A
Department of Ophthalmology, Juntendo University School of
Medicine, Tokyo, Japan.
Experimental Eye Research (United Kingdom), 1996, 62/4
(399-408)
Initial investigations done in this laboratory detected
increased albumin and decreased glyceraldehyde 3-phosphate
dehydrogenase concentrations in the retina of an animal model
manifesting early onset macular degeneration. Both
glyceraldehyde 3-phosphate dehydrogenase and albumin are
markers of oxidative stress in cells. In this study, we used
the same animal model to study further biochemical and
physiological processes which may be involved in the
pathogenesis of early onset macular degeneration in monkeys.
We detected 60% lower catalase and glutathione peroxidase
activities in the affected retinas suggesting lower
antioxidant activities and oxidative stress. One of the
consequences of oxidative stress is the production of
metallothionein, a low molecular weight protein also induced
by high concentrations of heavy metals such as zinc.
Metallothionein was detected by RT-PCR in these monkey
retinas. However initial quantitative PCR studies on this
protein showed that the synthesis of metallothionein in
affected retinas appears to be less than in normal controls.
The affected retinas also showed a fourfold lower zinc
concentration compared with the normal controls. No
significant difference, however, could be detected in the zinc
concentrations in plasma samples. Since induction of
metallothionein synthesis is mediated by transcription factors
which require heavy metals such as zinc for binding to
specific sites in the DNA, the lowered zinc concentration may,
thus, correlate with the lowered metallothionein expression.
And since metallothionein is suggested to function as a free
radical scavenger, the lowered metallothionein synthesis may
consequently contribute to increased peroxidation reactions in
the affected retinas. It appears therefore, that oxidative
stress and the decreased metallothionein synthesis may be
involved in the pathogenesis of early onset macular
degeneration in this animal model.
Association of zinc and antioxidant nutrients with
age-related maculopathy.
Mares-Perlman JA, Klein R, Klein BE, Greger JL, Brady WE,
Palta M, Ritter LL
Department of Ophthalmology, University of Wisconsin,
Madison, USA.
Arch Ophthalmol (United States) Aug 1996, 114 (8)
p991-7
OBJECTIVE: To quantify relationships between dietary intake
of zinc and antioxidant nutrients and early and late
age-related maculopathy (ARM).
DESIGN: A retrospective longitudinal cohort design using
data pertaining to diets in the past (1978-1980), which were
assessed retrospectively using a food frequency
questionnaire.
SETTING: Beaver Dam, Wis.
PATIENTS: A 50% random sample of free-living Beaver Dam Eye
Study participants, 43 to 86 years of age (N = 1968).
MAIN OUTCOME MEASURE: The presence of early and late ARM
determined from fundus photography.
RESULTS: People in the highest vs lowest quintiles for
intake of zinc from foods had lower risk for early ARM
(odds ratio = 0.6, 95% confidence interval, 0.4-1.0, P for
trend < .05). This relationship appeared to be stronger for
some types of early ARM (increased retinal pigment) than for
others. Zinc intake was unrelated to late ARM. However, small
numbers (n = 30) of people with this condition limit the
ability to draw conclusions about this later stage. Levels of
carotenoids were unrelated to early or late ARM. Odds for
early ARM were lower in people in the highest vs lowest
quintiles for the intake of vitamins C or E. However,
these associations were not statistically significant.
CONCLUSIONS: The data are weakly supportive of a protective
effect of zinc on the development of some forms of early ARM.
Prospective studies are needed to further evaluate the
potential influence of these and other nutritional factors on
different types and stages of age-related macular
degeneration.
Oral zinc and the second eye in age-related macular
degeneration.
Stur M, Tittl M, Reitner A, Meisinger V
Klinik fur Augenheilkunde, Abteilung A, Allgemeines
Krankenhaus der Stadt Wien, Austria.
Invest Ophthalmol Vis Sci (United States) Jun 1996, 37 (7)
p1225-35
PURPOSE. To investigate the short-term effect of oral zinc
substitution on the development of age-related macular
degeneration in the second eye of patients with an exudative
form of the disease in the first eye.
METHODS. A 2-year, double-masked, randomized,
placebo-controlled study including 112 white patients with
age-related macular degeneration and exudative lesions
(choroidal neovascularization, pigment epithelial detachment,
or both) in one eye and a visual acuity of better than 20/40
and macular degeneration without any exudative lesion in the
second eye was performed. Patients received either 200 mg of
oral zinc sulfate or placebo once daily for 24 months. The
main outcome parameters were visual acuity, contrast
sensitivity, color discrimination, and retinal grating acuity,
as well as serum levels of zinc and copper, red blood cell
count, hemoglobin, and morphologic changes detected by grading
of monochrome fundus photographs and fluorescein
angiograms.
RESULTS. In the treatment group, the mean zinc serum level
increased significantly (P < 0.0001) from 79 +/- 10
micrograms/dl to 108 +/- 26 micrograms/dl compared to no
change (82 +/- 16 micrograms/dl to 85 +/- 10 micrograms/dl) in
the placebo group. Serum levels of copper, hemoglobin, and red
blood cell count did not change significantly in either group.
A choroidal neovascular membrane (CNV) was detected in 14
patients during the treatment period (nine in the treatment
group, five in the placebo group). Seven additional patients
(three in the treatment group, four in the placebo group)
experienced visual loss caused by CNV, and in two patients
(one in each group), serous pigment epithelial detachment
developed without angiographic evidence of CNV after the end
of treatment, during a mean additional follow-up time of 20.8
+/- 8.2 months. In eyes in which exudative lesions did not
develop, there was no significant change in any of the
functional parameters during the 24-month treatment period,
but there was a significant increase in the nonexudative
alterations (drusen size, drusen confluence,
hyperpigmentation, and focal degeneration of the retinal
pigment epithelium) in both groups.
CONCLUSIONS. Oral zinc substitution has no short-term
effect on the course of age-related macular degeneration in
patients who have an exudative form of the disease in one
eye.
Dietary carotenoids, vitamins A, C, and E, and
advanced age-related macular degeneration. Eye Disease
Case-Control Study Group
Seddon JM; Ajani UA; Sperduto RD; Hiller R; Blair N; Burton
TC; Farber MD; Gragoudas ES; Haller J; Miller DT; et al
JAMA 1994 Nov 9;272(18):1413-20
Published erratum appears in JAMA 1995 Feb
22;273(8):622
OBJECTIVE--To evaluate the relationships between dietary
intake of carotenoids and vitamins A, C, and E and the risk of
neovascular age-related macular degeneration (AMD), the
leading cause of irreversible blindness among adults.
DESIGN--The multicenter Eye Disease Case-Control Study.
SETTING--Five ophthalmology centers in the United
States.
PATIENTS--A total of 356 case subjects who were diagnosed
with the advanced stage of AMD within 1 year prior to their
enrollment, aged 55 to 80 years, and residing near a
participating clinical center. The 520 control subjects were
from the same geographic areas as case subjects, had other
ocular diseases, and were frequency-matched to cases according
to age and sex.
MAIN OUTCOME MEASURES--The relative risk for AMD was
estimated according to dietary indicators of antioxidant
status, controlling for smoking and other risk factors, by
using multiple logistic-regression analyses.
RESULTS--A higher dietary intake of carotenoids was
associated with a lower risk for AMD. Adjusting for other risk
factors for AMD, we found that those in the highest quintile
of carotenoid intake had a 43% lower risk for AMD compared
with those in the lowest quintile (odds ratio, 0.57; 95%
confidence interval, 0.35 to 0.92; P for trend = .02). Among
the specific carotenoids, lutein and zeaxanthin, which are
primarily obtained from dark green, leafy vegetables, were
most strongly associated with a reduced risk for AMD (P for
trend = .001). Several food items rich in carotenoids were
inversely associated with AMD. In particular, a higher
frequency of intake of spinach or collard greens was
associated with a substantially lower risk for AMD (P for
trend < .001). The intake of preformed vitamin A (retinol)
was not appreciably related to AMD. Neither vitamin E nor
total vitamin C consumption was associated with a
statistically significant reduced risk for AMD, although a
possibly lower risk for AMD was suggested among those with
higher intake of Vitamin-C, particularly from foods.
CONCLUSION--Increasing the consumption of foods rich in
certain carotenoids, in particular dark green, leafy
vegetables, may decrease the risk of developing advanced or
exudative AMD, the most visually disabling form of macular
degeneration among older people. These findings support the
need for further studies of this relationship.
Evidence by in vivo and in vitro studies that
binding of pycnogenols to elastin affects its rate of
degradation by elastases
Tixier J.M.; Godeau G.; Robert A.M.; Hornebeck W.
Biochem Pharmacol 1984 Dec 15;33(24):3933-9
Procyanidol oligomers and (+) catechin bound to insoluble
elastin markedly affect its rate of degradation by elastases.
Insoluble elastin pretreated with procyanidol oligomers (PCO)
was resistant to the hydrolysis induced by both porcine
pancreatic and human leukocyte elastases. The quantitative
adsorption of pancreatic elastase was similar on either
untreated or PCO-treated elastin suggesting that the binding
of this compound to elastin increases the non-productive
catalytic sites of elastase molecules. (+)
Catecholin-insoluble elastin complexes were partially
resistant to the degradation induced by human leukocyte
elastase but were not hydrolysed at the same rate as untreated
samples by a constant amount of pancreatic elastase. In
addition, the coacervation profile of kappa-elastin peptides
as a function of temperature is greatly modified in presence
of these flavonoids. We conclusively evidenced that PCOs bind
to skin elastic fibres when injected intradermally into young
rabbits. As a result, these elastic fibres were found more
resistant to the hydrolytic action of porcine pancreatic
elastase when injected to the same site. These in vivo studies
emphasized the potential effect of these compounds in
preventing elastin degradation by elastase(s) as occurred in
inflammatory processes.
Antioxidant enzymes of the human retina: Effect of
age on enzyme activity of macula and periphery
De La Paz M.A.; Zhang J.; Fridovich I.
Duke University Eye Center, DUMC, Box 3802, Durham, NC 27710
USA
Current Eye Research (United Kingdom), 1996, 15/3
(273-278)
The purpose of this research was to evaluate the effect of
age on protective antioxidant enzyme activity of normal fresh
cadaver human retina of the macula and periphery. Antioxidant
enzymes were assayed in tissue extracts generated from 5 mm
trephined punches of retina obtained centered over the macula
and the superior midperiphery of normal fresh human cadaver
retina. Cadaver tissue was obtained from donors of a wide age
range (age 7 to 85 years). The assays were performed within 6
h of enucleation and within 24 h of donor death. Antioxidant
enzymes assayed included superoxide dismutase, catalase,
glutathione peroxidase, and glutathione reductase. Hexokinase
and glucose-6-phosphate dehydrogenase, enzymes not directly
involved in protection against oxidative damage, were assayed
for comparison. Enzyme specific activities were calculated for
the macula and periphery using protein concentration of the
extract as the denominator. Using linear regression analysis,
over the age range of 25 to 75 years, superoxide dismutase
activity of the periphery but not the macula tended to decline
with age (p = 0.04, R2 = 0.21). Interindividual variability
was high, and variability increased with age. The difference
between the macular and peripheral enzyme activities for
glutathione peroxidase tended to decline with increasing donor
age (p = 0.025, R2 = 0.33). There was no effect of age on the
specific activities of catalase, glucose-6-phosphate
dehydrogenase, and glutathione reductase. The specific
activity of hexokinase from the macula declined with
increasing donor age (p = 0.022, R2 = 0.43). Time from death
to enucleation or beginning of experiment was not a
significant factor. In summary, age does not have an effect on
the activity of major antioxidant enzymes of the macula in
normal human retina. There is a tendency for an effect of age
on peripheral superoxide dismutase activity and the difference
between macular and peripheral glutathione peroxidase
activity. High interindividual variability of antioxidant
enzyme activity exists in humans.
Low glutathione reductase and peroxidase activity
in age-related macular degeneration
Cohen S.M.; Olin K.L.; Feuer W.J.; Hjelmeland L.; Keen C.L.;
Morse L.S.
Department of Ophthalmology, UC Davis, 1603 Alhambra
Boulevard, Sacramento, CA 95816 USA
Br. J. Ophthalmol. (United Kingdom), 1994, 78/10
(791-794)
Age-related macular degeneration (ARMD) may result from
events initiated by reactive oxygen species. Blood samples
from 18 patients with ARMD and 18 similarly aged controls were
analysed for activities of important antioxidants. Blood
glutathione reductase activity was lower in patients with ARMD
compared with controls (p = 0.035). The activities of
glutathione peroxidase (p = 0.18) and erythrocyte superoxide
dismutase (p = 0.29) were similar between the two groups by a
Student's two sample t test. Logistic regression was used to
determine which enzyme activities were associated with ARMD
after adjusting for possible confounding variables: smoking
history, age, multivitamin use, and cardiovascular disease.
Glutathione reductase activity (p = 0.05) and glutathione
peroxidase activity (p = 0.065) were significantly associated
with ARMD by this analysis. The relation of glutathione
reductase and glutathione peroxidase activity to ARMD merits
further study.
Antioxidant enzymes in RBCs as a biological index
of age related macular degeneration
Prashar S.; Pandav S.S.; Gupta A.; Nath R.
Department of Biochemistry, PGIMER, Chandigarh 160012
India
Acta Ophthalmol. (Denmark), 1993, 71/2 (214-218)
The present study was undertaken to assess the levels of
antioxidant enzymes in red blood cells of subjects with
age-related macular degeneration and age-matched controls. The
results obtained show a significant decrease in activities of
superoxide dismutase (p < 0.001) and glutathione peroxidase
(p < 0.001) as compared to the controls. A good correlation
(r =O.99) was also observed between age and decreased activity
of antioxidant enzymes in controls, and also correlated well
with age related macular degeneration. In conclusion,
oxidative stress as assessed by antioxidant enzymes is more
pronounced in subjects with age-related macular degeneration
as compared to age-matched controls.
Oxidative effects of laser photocoagulation
Jennings P.E.; MacEwen C.J.; Fallon T.J.; Scott N.; Haining
W.M.; Belch J.J.F.
Department of Medicine, Ninewells Hospital and Medical
School, Dundee, DD19SY United Kingdom
Free Radic. Biol. Med. (USA), 1991, 11/3
(327-330)
Diabetic proliferative retinopathy is a common and
sight-threatening condition. Oxidative stress is an integral
and possibly causative part of the pathogenesis. Although
laser photocoagulation is usually a beneficial treatment it
remains unclear how it works. The possibility that it induces
a sudden, temporary increase in free radical activity either
by direct thermal damage or by oxygen reperfusion is explored
in this clinical study by measuring the oxidative status in
the peripheral blood of 13 patients undergoing panretinal
photocoagulation. There were significant increases at one hour
in malondialdehyde-like material (MDA-LM), 8.1 (6.9-9.6)
nmol/mL, to 9.1 (7.6-9.8) nmol/mL, (< 0.005); plasma thiols
(PSH), 423 (352-457) microm/L, to 444 (382-478) microm/L, (p
< 0.005) and red cell reduced glutathione (GSH), 1357
(1295-1655) microm/L, to 1480 (1305-1760) microm/L, (p <
0.01). Diene conjugates rose over the first hour 0.55
(0.36-0.79) od/mL, to 0.58 (0.34-0.85) od/mL falling to 0.56
(0.36-0.79) od/mL at 2 h but these changes were not
significant. At 2 h, MDA-LM 8.4 (6.7-9.6) nmol/mL and PSH 404
(379-462) microm/L had returned to baseline but GSH remained
significantly elevated 1500 (1325-1675) microm/L, (p <
0.005 compared to baseline). This is a new observation and in
some circumstances such generation of free radicals could
explain the mechanism behind the complications of
photocoagulation by direct or indirect damage to vascular
endothelium leading to increased vascular permeability
manifest as macular oedema or choroidal effusions.
Antioxidant status and neovascular age-related
macular degeneration
Yannuzzi L.A.; Sorenson J.A.; Sobel R.S.; Daly J.R.; DeRosa
J.T.; Seddon J.M.; Gragoudas E.S.; Puliafito C.A.; Gelles E.;
Gonet R.; Burton T.C.; Culver J.; Metzger K.; Kalbfleisch N.;
Zarling D.; Farber M.D.; Blair N.; Stelmack T.; Sperduto R.D.;
et al.
Biometry and Epidemiology Program, National Eye Institute,
Bldg 31, 9000 Rockville Pike, Bethesda, MD 20892 USA
Arch. Ophthalmol. (USA), 1993, 111/1 (104-109)
We evaluated the hypothesis that higher serum levels of
micronutrients with antioxidant capabilities may be associated
with a decreased risk of neovascular age-related macular
degeneration by comparing serum levels of carotenoids,
vitamins C and E, and selenium in 421 patients with
neovascular age-related macular degeneration and 615 controls.
Subjects were classified by blood level of the micronutrient
(low, medium, and high). Persons with carotenoid levels in the
medium and high groups, compared with those in the low group,
had markedly reduced risks of neovascular age-related macular
degeneration, with levels of risk reduced to one half and one
third, respectively. Although no statistically significant
protective effect was found for Vitamin-C or E or selenium
individually, an antioxidant index that combined all four
micronutrient measurements showed statistically significant
reductions of risk with increasing levels of the index.
Although these results suggest that higher blood levels of
micronutrients with antioxidant potential, in particular,
carotenoids, may be associated with a decreased risk of the
most visually disabling form of age-related macular
degeneration, it would be premature to translate these
findings into nutritional recommendations.
Nutrition in the elderly
Morley J.E.; Mooradian A.D.; Silver A.J.; Heber D.;
Alfin-Slater R.B. BR> Department of Medicine, University of
California School of Medicine, Los Angeles, CA 90024 USA
Ann. Intern. Med. (USA), 1988, 109/11 (890-904)
Nutritional modulation is one approach to successful aging.
In animals, dietary restriction increases life span.
Alterations in the macronutrient and micronutrient constituent
of the diet can modulate gene expression. Anorexia is common
in elderly persons. The results of studies in animals suggest
that aging is associated with a decrease in the opioid feeding
drive and an increase in the satiating effect of
cholecystokinin. Unrecognized depression is a common,
treatable cause of anorexia and weight loss in elderly
persons. Protein synthesis decreases in elderly persons;
nevertheless, nitrogen balance can be maintained in patients
with fairly low intakes of protein. Carbohydrate intolerance
is common and may be modulated by nutritional intervention and
physical activity. The role of cholesterol in the development
of heart disease in very old persons is controversial.
Homebound and institutionalized elderly persons often do not
expose their skin to sunlight; because the skin of older
persons has a decreased ability to form vitamin D, the vitamin
D status in these persons is precarious and they are at risk
for osteopenia. Vitamins are often abused by elderly persons.
Drug administration alters the vitamin requirements of
persons. Borderline zinc state has been associated with
deteriorating immune function, especially in persons who have
diabetes mellitus or who abuse alcohol. Zinc administration
appears to protect against the deteriorating vision associated
with age-related macular degeneration. Selenium deficiency
seems to be associated with an increased prevalence of
cancer.
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