Subclinical Vitamin Research Articles

Hypovitaminosis A in Brazil: a public health problem

Vitamin A deficiency is considered one of the most important of the easily preventable public health problems in a number of countries, including Brazil. The objective of this study was to review the scientific literature in the MEDLINE and LILACS databases that was published between 1970 and 2000 concerning vitamin A deficiency, and to assess the occurrence of hypovitaminosis A in Latin America, especially Brazil. Our research showed that until around 1980 the public health concerns focused mainly on the importance of vitamin A in ensuring good vision. In the second half of the 1980s, epidemiological studies suggested that, on a population level, subclinical vitamin A deficiency could also have a negative effect on metabolic functions, with a great impact on childhood morbidity and mortality. Marginal vitamin A deficiency has been reported in all the regions of Brazil for which there are data available, with high prevalences in various age groups. This situation is inexcusable, given the health care technology and resources that are now available. There must be a commitment to reducing vitamin A deficiency in order to ensure the adequate development of future generations.

Effects of vitamin A deficiency during pregnancy on maternal and child health

Objective To examine the association between biochemical vitamin A deficiency in pregnancy and maternal and fetal health. Design A cross sectional clinical study. Setting Antenatal clinic of nutrition unit of Niloufer Hospital catering for a low socio-economic population, and a private nursing home (Swapna nursing home) catering for a high socio-economic population. Population 736 pregnant women in their third trimester of pregnancy belonging to low ( n = 522) and high socio-economic groups ( n = 214). Methods All the women were subjected to a detailed clinical, anthropometric and obstetric examination. Night blindness was assessed by administering the standard WHO questionnaire. Birthweight and gestational age of the infants, maternal anaemia and development of pregnancy-induced hypertension in the mother were recorded. Haemoglobin and serum retinol were estimated at the time of recruitment to the study. Main outcome measures Serum retinol levels, anaemia, pregnancy-induced hypertension, birthweight and gestational age of the infant. Results Night blindness was observed in 2.9% of the women and subclincal vitamin A deficiency (serum retinol <20 μg/dL with no clinical signs) in 27% of the women. Moderate to severe anaemia was observed in 41.2% of the women, and 15.8% of the women developed pregnancy-induced hypertension. Sixty-one (9.4%) women delivered preterm. Univariate analysis identified a significant association between serum retinol <20 μg/dL and preterm delivery (OR = 1.74, 95% CI 1.03–2.96), maternal anaemia (OR = 1.82, 95% CI 1.28–2.60) and pregnancy-induced hypertension (OR = 1.56, 95% CI 1.02–2.83). After adjusting for the confounding variables (body mass index, parity, age and socio-economic status) in a multivariate analysis, the significant associations between serum retinol <20 μg/dL and preterm delivery ( P = 0.02) and anaemia ( P = 0.003) persisted, while that for pregnancy-induced hypertension disappeared ( P = 0.71). Conclusion The study suggests that subclinical vitamin A deficiency is a problem during the third trimester of pregnancy. Serum concentration of retinol <20 μg/dL appears to indicate a deficient status, and is associated with an increased risk of preterm delivery and maternal anaemia.

Effects of vitamin A deficiency during pregnancy on maternal and child health.

To examine the association between biochemical vitamin A deficiency in pregnancy and maternal and fetal health. A cross sectional clinical study. Antenatal clinic of nutrition unit of Niloufer Hospital catering for a low socio-economic population, and a private nursing home (Swapna nursing home) catering for a high socio-economic population. 736 pregnant women in their third trimester of pregnancy belonging to low (n = 522) and high socio-economic groups (n = 214). All the women were subjected to a detailed clinical, anthropometric and obstetric examination. Night blindness was assessed by administering the standard WHO questionnaire. Birthweight and gestational age of the infants, maternal anaemia and development of pregnancy-induced hypertension in the mother were recorded. Haemoglobin and serum retinol were estimated at the time of recruitment to the study. Serum retinol levels, anaemia, pregnancy-induced hypertension, birthweight and gestational age of the infant. Night blindness was observed in 2.9% of the women and subclincal vitamin A deficiency (serum retinol <20 microg/dL with no clinical signs) in 27% of the women. Moderate to severe anaemia was observed in 41.2% of the women, and 15.8% of the women developed pregnancy-induced hypertension. Sixty-one (9.4%) women delivered preterm. Univariate analysis identified a significant association between serum retinol <20 microg/dL and preterm delivery (OR = 1.74, 95% CI 1.03-2.96), maternal anaemia (OR = 1.82, 95% CI 1.28-2.60) and pregnancy-induced hypertension (OR = 1.56, 95% CI 1.02-2.83). After adjusting for the confounding variables (body mass index, parity, age and socio-economic status) in a multivariate analysis, the significant associations between serum retinol <20 microg/dL and preterm delivery (P = 0.02) and anaemia (P = 0.003) persisted, while that for pregnancy-induced hypertension disappeared (P = 0.71). The study suggests that subclinical vitamin A deficiency is a problem during the third trimester of pregnancy. Serum concentration of retinol <20 microg/dL appears to indicate a deficient status, and is associated with an increased risk of preterm delivery and maternal anaemia.

Serum 25-hydroxyvitamin D status of adolescents and adults in two seasonal subpopulations from NHANES III

Subclinical vitamin D deficiency may be common in certain subgroups in the U.S., but to date vitamin D data from other groups in the population have not been available. We used serum 25-hydroxyvitamin D (25-OHD) data from 18,875 individuals examined in the Third National Health and Nutrition Examination Survey (NHANES III 1988–1994) to assess the vitamin D status of selected groups of the noninstitutionalized U.S. adolescent and adult population. Serum 25-OHD levels were measured by a radioimmunoassay kit (DiaSorin, Inc., Stillwater, MN; normal range 22.5–94 nmol/L). Because physical exams are performed in mobile vans in NHANES, data could not be collected in northern latitudes during the winter; instead data were collected in northern latitudes during summer and in southern latitudes in winter. To address this season-latitude aspect of the NHANES design, we stratified the sample into two seasonal subpopulations (winter/lower latitude and summer/higher latitude) before examining vitamin D status. Less than 1% of the winter/lower latitude subpopulation had vitamin D deficiency (25-OHD <17.5 nmol/L). However, the prevalence of vitamin D insufficiency in this group ranged from 1%–5% with 25-OHD <25 nmol/L to 25%–57% with 25-OHD <62.5 nmol/L, even though the median latitude for this subsample (32°N) was considerably lower than the latitude at which vitamin D is not synthesized during winter months (∽42°N). With the exception of elderly women, prevalence rates of vitamin D insufficiency were lower in the summer/higher latitude subpopulation (<1%–3% with 25-OHD <25 nmol/L to 21%–49% with 25-OHD <62.5 nmol/L). Mean 25-OHD levels were highest in non-Hispanic whites, intermediate in Mexican Americans, and lowest in non-Hispanic blacks. Our findings suggest that vitamin D deficiency is unlikely in the two seasonal subpopulations of noninstitutionalized adolescents and adults that can be validly assessed in NHANES III. However, vitamin D insufficiency is more common in these two seasonal subpopulations. Of particular interest is that insufficiency occurred fairly frequently in younger individuals, especially in the winter/lower latitude subsample. Our findings support continued monitoring of this vitamin in the U.S. population.

Differential Diagnosis of Osteoporosis

Background: Dual x-ray absorptiometry (DEXA) is widely used to identify persons at increased risk for osteoporotic fractures. It does not, per se, give us any diagnostic information that is necessary to determine the best therapeutic approach in an individual case. Objective: Identify conditions and tests that may impact on the diagnosis and the treatment of subjects with low bone densitometry scores. Subjects and Methods: We evaluated clinically, by history, physical examination and laboratory tests, 272 persons with low spinal and/or femoral bone absorptiometry for potential causes of osteoporosis. Results: We found that 25.3% of the patients had significant underlying conditions: 17.9% had subclinical vitamin D deficiency (osteomalacia), 6.7% had hypercalciuria and 0.7% had primary hyperparathyroidism. Conclusion: It is mandatory to go through a differential diagnosis in every case with absorptiometric data compatible with the diagnosis of osteoporosis. At the minimum, blood calcium and 25-hydroxyvitamin D and 24-hour urinary calcium excretion should be examined. This will allow the physician to determine the appropriate course of therapy in any individual patient who has abnormal DEXA findings.

High Prevalence of Subclinical Vitamin A Deficiency in Jordan: A Forgotten Risk

This longitudinal study assessed growth and vitamin A status of schoolchildren after earlier surveys had linked stunting among Jordanian children to dietary zinc and iron inadequacies. A group of 1,023 subjects ages 5.5 to 9.9 years were randomly recruited for study from seven disadvantaged semirural districts. Baseline assessment included anthropometric and laboratory data with the relevant dietary information. Over nine months of study, the subjects received a daily snack meal. Immediately before the final assessment, each student received one 100,000 IU vitamin A capsule. At baseline there was a 19.9% prevalence of stunting, 18.8% for anemia, and 21.8% for subclinical vitamin A deficiency. Mean and median serum retinol concentrations were 248 (sd +/- 66) and 242 micrograms/L, respectively. In 98% of the cases, vitamin A-rich vegetables were consumed three or more days per week. About 60% of subjects had serum retinol levels in the range 200 to 300 micrograms/L. Only vitamin A foods from animal sources showed an influence (p < .05) on mean serum vitamin A values and growth score. Dietary and capsule supplementation had a significant positive impact only on serum retinol levels (p < .01) and on the anemia (p < .05) indicators. The conclusion underlines vitamin A deficiency among schoolchildren as a public health problem, and that the situation is anticipated to be more profound among preschool children, who are usually at greater risk of becoming deficient. Launching another, but controlled, intervention study in other sites, preferably with use of a tracer to rule out malabsorption in young children, is highly indicated.

Development and validation of a short food-frequency questionnaire for screening women of childbearing age for vitamin A status in northwestern Iran.

A high percentage of women in their childbearing years suffer from subclinical vitamin A deficiency; 10% to 20% of pregnant women worldwide are vitamin A deficient. This study aimed to design and validate a short food-frequency questionnaire to serve as a simple screening tool for vitamin A status in women of childbearing age. The sample consisted of 187 healthy, nonpregnant, nonlactating women 15 to 49 years of age, from urban and rural areas of Marand district in East Azerbaijan. Dietary intake was evaluated by a face-to-face interview using a 24-hour dietary recall for two consecutive days and a 41-item qualitative food frequency questionnaire. Height, weight, and serum retinol were measured. Serum retinol values were less than 20 micrograms/dl for three subjects, while an additional 34 subjects (18%) had values between 21 and 30 micrograms/dl. Principal-component analysis performed on the food-frequency questionnaire identified five components that together defined 34.4% of the variance in estimated vitamin A intake and were used to derive a 20-item short food-frequency questionnaire. Internal consistency of the short instrument was acceptable (Cronbach's alpha = .59). Serum retinol was significantly correlated with total vitamin A intake and with intake of vitamin A from plant sources, as estimated by the short food-frequency questionnaire. Important sources of provitamin A in these women's diets included some not typical of other populations: nuts and green leaves of types used elsewhere in small quantities as herbs, but important in Iran because the amount and frequency of consumption are relatively high. We conclude that the questionnaire is relatively valid and potentially useful in identifying women at risk for vitamin A deficiency in this population.

Vitamina K: metabolismo e nutrição

O objetivo desta revisão foi discutir aspectos que envolvem a compreensão do metabolismo da vitamina K e os recentes avanços quanto ao papel da vitamina na nutrição humana. São abordadas questões sobre as fontes da vitamina, sua absorção, distribuição e metabolismo, recomendações dietéticas, avaliação do estado nutricional relacionado à vitamina K e ainda fatores que afetam sua concentração plasmática. Diante das novas evidências sobre a participação da vitamina K no metabolismo ósseo, pesquisas adicionais são necessárias a fim de identificar as possíveis conseqüências à saúde, a longo prazo, de deficiência subclínica desta vitamina. Pesquisadores e comitês futuros encontram um desafio no que se refere a investigar novos requerimentos nutricionais da vitamina.

Longitudinal evaluation of vitamin D status in healthy subjects from southern Italy: seasonal and gender differences.

Vitamin D status is currently considered among the relevant determinants of skeletal integrity. Since vitamin D levels present seasonal variations, we longitudinally studied young healthy men and women in order to investigate the related physiologic modifications of both calcium homeostasis and bone remodeling. Thirty-two men (mean age 39.4 +/- 7.8 years) and 58 premenopausal women (aged 36.9 +/- 6.4 years) from southern Italy were studied. In all subjects the following parameters were measured both in winter and in summer: serum calcium, phosphorus, creatinine, total alkaline phosphatase activity, 25-hydroxyvitamin D (25OHD), parathyroid hormone (PTH), osteocalcin (BGP), together with urinary calcium (Ca/Cr), total pyridinoline (Pyr/Cr) and deoxypyridinoline (d-Pyr/Cr), corrected for creatinine excretion. In both sexes 25OHD levels were significantly higher in summer, while PTH values were lower, than in winter. The prevalence of hypovitaminosis D, defined by concentrations of 25OHD lower than 30 nmol/l, was 17.8% in winter and 2.2% in summer in the whole sample, while it was 27.8% and 3.4%, respectively, among female subjects. Indeed male subjects did not display hypovitaminosis D, having throughout the year significantly higher calcium and 25OHD levels together with lower PTH values, than the women. Moreover, alkaline phosphatase total activity was more elevated in men both in winter and in summer. In women, during winter, bone remodeling markers levels were higher while urinary calcium levels were lower than in summer. In the whole sample serum 25OHD correlated positively with serum calcium and inversely with PTH. The seasonal percentage variations in PTH were inversely correlated with those of Ca/Cr. Our results show a relatively high prevalence of subclinical vitamin D deficiency among young healthy women from southern Italy. Significant gender-specific differences have been demonstrated in both calcium homeostasis and skeletal remodeling indexes; the seasonal fluctuations in the vitamin D-PTH axis are accompanied by cyclical variations of bone turnover rate, which were more pronounced in women.

Vitamin D deficiency and associated factors in adolescent girls in Beijing

Several locally published reports indicate a high prevalence of vitamin D deficiency among adolescents in China, but no systematic population-based survey has been conducted. The objective was to determine the prevalence of vitamin D deficiency and to study associated factors in adolescent girls in Beijing. A cross-sectional study was conducted in a random sample of 1248 Beijing girls aged 12-14 y. Nutrient intakes, ultraviolet light exposure, anthropometric characteristics, physical activity, signs and symptoms of rickets, and plasma concentrations of 25-hydroxyvitamin D, 1,25-dihydroxyvitamin D, and calcium were measured and X-rays of the hand and wrist were taken. The prevalence of clinical vitamin D and calcium deficiency (plasma 25-hydroxyvitamin D <12.5 nmol/L, plasma calcium <2.25 mmol/L, and muscle spasm at least once per week) was 9.4% in winter. The prevalence of subclinical vitamin D deficiency (25-hydroxyvitamin D <12.5 nmol/L) was 45.2% in winter and 6.7% in summer (P < 0.0005). Logistic regression analysis showed that subclinical and clinical vitamin D deficiency in winter were associated with low plasma 25-hydroxyvitamin D concentrations (<12.5 nmol/L) in summer, low calcium intake ( x +/- SD: 280 +/- 48 compared with 440 +/- 61 mg/d), and low plasma calcium concentrations (<2.25 mmol/L) in winter. The odds ratios for these associations were 3.1, 1.5, and 1.5, respectively. Subclinical vitamin D deficiency was widespread among Beijing adolescent girls in winter. Low plasma 25-hydroxyvitamin D concentrations in summer, low calcium intake, and low plasma calcium concentrations in winter were the main risk factors for vitamin D deficiency in winter.

Vitamin D status and redefining serum parathyroid hormone reference range in the elderly.

Subclinical vitamin D insufficiency is characterized by mild secondary hyperparathyroidism and enhanced risk of osteoporotic fracture. However, although low levels of 25-hydroxyvitamin D (25OHD) are common in otherwise normal elderly people, vitamin D status has not generally been taken into account in the previously published reference values for serum PTH. We measured fasting morning serum (obtained from April through June) PTH, total calcium, albumin, phosphate, creatinine, bone markers, and 25OHD in 280 healthy subjects (140 men and 140 women), aged 60-79 yr. Serum PTH was measured by means of 2 immunoradiometric assays, the Allegro intact PTH assay (Nichols Institute Diagnostics) and the new CAP assay (Scantibodies Laboratory, Inc.). We found a high prevalence (167 of 280; 59.6%) of low 25OHD (< or =30 nmol/L) in these otherwise healthy individuals. The PTH concentrations (95% confidence interval) obtained in the whole group of 280 subjects ranged from 13-64 ng/L for the Allegro assay and from 10-44 ng/L for the CAP assay. In the subjects with a serum 25OHD concentration greater than 30 nmol/L, values for both PTH assays were lower, 10-46 and 9-34 ng/L for the Allegro and the CAP assays, respectively. By using these values as a reference range, approximately 25% of the subjects with a serum 25OHD level of 30 nmol/L or less had a high serum PTH level (whatever the assay), reflecting secondary hyperparathyroidism. This might be missed if the reference PTH values are those obtained in the entire group, as is usually done. These results strongly suggest that vitamin D status should be taken into account when establishing reference values for serum PTH in elderly subjects.

Serum vitamin C concentration is low in peripheral arterial disease and is associated with inflammation and severity of atherosclerosis.

Peripheral arterial disease (PAD) is a severe atherosclerotic condition frequently accompanied by inflammation and oxidative stress. We hypothesized that vitamin C antioxidant levels might be low in PAD and are related to inflammation and disease severity. We investigated vitamin C (L-ascorbic acid) levels in 85 PAD patients, 106 hypertensives without PAD, and 113 healthy subjects. Serum L-ascorbic acid concentrations were low among PAD patients (median, 27.8 micromol/L) despite comparable smoking status and dietary intake with the other groups (P<0.0001). Subclinical vitamin C deficiency (<11.4 micromol/L), confirmed by low serum alkaline phosphatase activity, was found in 14% of the PAD patients but not in the other groups. Serum C-reactive protein (CRP) concentrations were significantly higher in PAD patients (P<0.0001) and negatively correlated with L-ascorbic acid levels (r=-0.742, P<0.0001). In stepwise multivariate analysis, low L-ascorbic acid concentration in PAD patients was associated with high CRP level (P=0.0001), smoking (P=0.0009), and shorter absolute claudication distance on a standardized graded treadmill test (P=0.029). Vitamin C concentrations are lower in intermittent claudicant patients in association with higher CRP levels and severity of PAD. Future studies attempting to relate vitamin C levels to disease occurrence should include in their analysis an inflammatory marker such as CRP.

Reducing Subclinical Vitamin A Deficiency through Women's Adoption of Appropriate Technologies in Tanzania

Many at-risk populations in developing countries are vitamin A deficient. Improvement in the vitamin A status of preschool children would increase their chances of survival and improve their health. Progress has been made in combating severe forms of vitamin A deficiency, yet the extent of subclinical vitamin A deficiency is worrisome. Strategies such as supplementation, food fortification, and dietary diversification have had some impact, but efforts must be made to enhance their effectiveness. One promising strategy is to increase women's access to food-processing technologies that extend the availability of vitamin A and provitamin vitamin A–rich foods, reduce nutrient losses due to traditional processing methods, and improve the hygienic and nutritional quality of the dried food products. Because women are key to household nutrition, improving their access to such technologies would increase women's productivity and enhance the effectiveness of their nutrition-promoting behaviors. The Tanzania Food and Nutrition Centre (TFNC) within the Ministry of Health, and working with the Ministries of Agriculture and Livestock Development and Community Development, Children and Women's Affairs, implemented an intervention research study in rural Tanzania to promote women's adoption of improved solar-drying technologies for preserving vegetables and fruits and to improve children's dietary intake of provitamin A–containing foods. Children whose mothers adopted the improved solar dryers consumed significantly more foods rich in vitamin A and provitamin A (p &lt; .001). The β-carotene content of green leafy vegetables dried in the improved enclosed dryers was better than that of vegetables dried using traditional methods. These results suggest opportunities to reduce seasonal subclinical deficiencies among children in this semiarid rural area of Tanzania.

Nutrition activities in South Africa

South Africa has had a history of racial inequities. The poverty rate in the black population is more than 60%, compared with less than 5% for the Indian and white populations. Poverty is particularly severe in non-urban areas, where the rate is 73.7%. The inequalities in socio-economic status have been mirrored in the nutritional status of South Africans; on the one hand we have stunted, underweight children, while on the other, obese adults at risk for chronic diseases of lifestyle. Much of the previous nutrition research in South Africa concentrated on nutritional diseases of lifestyle of the higher socio-economic groups; however in the new democratic dispensation there has been a move towards research in the area of under-nutrition. In fact, the very first large research study in South Africa’s new democracy (1994) was the first ever, truly representative national nutrition survey of children under the age of six [1]. This survey revealed that stunting was a major problem as was sub-clinical vitamin A deficiency. These disorders were more pronounced in the historically disadvantaged provinces and in rural compared to urban areas. To address nutritional problems in South Africa, the Integrated Nutrition Programme was established by the government in 1996. This program aims to combine direct nutrition interventions, such as nutrition education, micronutrient supplementation and food fortification, with indirect interventions such as health care, provision of safe and clean water, agricultural production and parasite control [2]. The main aims of the program are to: Enable all mothers to exclusively breastfeed their

Vitamin K supplementation reduces serum concentrations of under-γ-carboxylated osteocalcin in healthy young and elderly adults

Subclinical vitamin K insufficiency, manifested by under-gamma-carboxylation of the bone matrix protein osteocalcin, may be common. Our objective was to delineate the prevalence of submaximal gamma-carboxylation as assessed by response to phylloquinone supplementation and to evaluate the effect of this intervention on skeletal turnover in healthy North American adults. Healthy subjects (n = 219), approximately equally distributed by sex and age (18-30 y and >/=65 y), received daily phylloquinone (1000 microg) or placebo for 2 wk. Serum undercarboxylated osteocalcin (ucOC) and total osteocalcin, N:-telopeptides of type I collagen (NTx), bone-specific alkaline phosphatase (BSAP), and phylloquinone concentrations were measured at baseline and after weeks 1 and 2. At baseline, the mean serum phylloquinone concentration was lower in the young than in the old group; there was no effect of sex. Concomitantly, baseline %ucOC was highest in the young and lowest in the old men (P: < 0.0001) but did not differ significantly by age in women. After supplementation, serum phylloquinone concentration increased approximately 10-fold (P: < 0.0001) at week 1 (from 0.93 +/- 0.08 to 8.86 +/- 0.70 nmol/L, x+/- SEM); this was sustained through week 2. Among all supplemented groups, mean %ucOC decreased from 7.6% to 3. 4% without significant differences by age or sex; 102 of 112 subjects had a >1% decrease. Phylloquinone supplementation reduced serum osteocalcin but did not alter NTx or BSAP concentration. Usual dietary practices in this population did not provide adequate vitamin K for maximal osteocalcin carboxylation. Phylloquinone supplementation reduced serum osteocalcin concentration but did not alter other markers of serum bone turnover.

Risk factors for subclinical vitamin A deficiency in children under the age of 6 years.

The present study was carried out to investigate risk factors for subclinical vitamin A deficiency in children under 6 years of age in the urban slums of Nagpur, India. The study included 308 nonxerophthalmic children selected randomly from the study population. On the basis of conjunctival impression cytology the prevalence of subclinical vitamin A deficiency was estimated to be 35.7 per cent. The current study recognised a significant association between female gender, illiterate mother, lower socioeconomic status, more than two children under 5 years of age at home, undernutrition, history of diarrhoea, measles, acute respiratory infections, and subclinical vitamin A deficiency on univariate analysis. Logistic regression analysis identified significance of female gender, more than two children under 5 years of age at home, undernutrition, and measles in the outcome of subclinical vitamin A deficiency. Estimates of attributable risk proportions and population attributable risk proportions for significant and preventable risk factors confirmed their etiological and preventable role in subclinical vitamin A deficiency respectively.

Vitamin C prevents cigarette smoke–induced oxidative damage in vivo

Our recent in vitro results [4] indicate that cigarette smoke induces oxidation of human plasma proteins and extensive oxidative degradation of the guinea pig lung, heart, and liver microsomal proteins, which is almost completely prevented by ascorbic acid. In this paper, we substantiate the in vitro results with in vivo observations. We demonstrate that exposure of subclinical or marginal vitamin C–deficient guinea pigs to cigarette smoke causes oxidation of plasma proteins as well as extensive oxidative degradation of the lung microsomal proteins. Cigarette smoke exposure also results in some discernible damage of the heart microsomal proteins. The oxidative damage has been manifested by SDS-PAGE, accumulation of carbonyl and bityrosine, as well as loss of tryptophan and protein thiols. Cigarette smoke exposure also induces peroxidation of microsomal lipids as evidenced by the formation of conjugated dienes, malondialdehyde, and fluorescent pigment. Cigarette smoke–induced oxidative damage of proteins and peroxidation of lipids are accompanied by marked drop in the tissue ascorbate levels. Protein damage and lipid peroxidation are also observed in cigarette smoke–exposed pair-fed guinea pigs receiving 5 mg vitamin C/animal/day. However, complete protection against protein damage and lipid peroxidation occurs when the guinea pigs are fed 15 mg vitamin C/animal/day. Also, the cigarette smoke–induced oxidative damage of proteins and lipid is reversed after discontinuation of cigarette smoke exposure accompanied by ascorbate therapy. The results, if extrapolated to humans, indicate that comparatively large doses of vitamin C may protect the smokers from cigarette smoke–induced oxidative damage and associated degenerative diseases.

The vitamin A spectrum: from deficiency to toxicity

Dark adaptation has been used as a tool for identifying patients with subclinical vitamin A deficiency. With this functional test it was shown that tissue vitamin A deficiency occurs over a wide range of serum vitamin A concentrations. However, serum vitamin A concentrations >1.4 micromol/L predict normal dark adaptation 95% of the time. Other causes of abnormal dark adaptation include zinc and protein deficiencies. Stable isotopes of vitamin A and isotope-dilution techniques were used recently to evaluate body stores of vitamin A and the efficacy of vitamin A intervention programs in field settings and are being used to determine the vitamin A equivalences of dietary carotenoids. Vitamin A toxicity was described in patients taking large doses of vitamin A and in patients with type I hyperlipidemias and alcoholic liver disease. Conversely, tissue retinoic acid deficiency was described in alcoholic rats as a result of hepatic vitamin A mobilization, impaired oxidation of retinaldehyde, and increased destruction of retinoic acid by P450 enzymes. Abnormal oxidation products of carotenoids can cause toxicity in animal models and may have caused the increased incidence of lung cancer seen in 2 epidemiologic studies of the effects of high-dose beta-carotene supplementation. Major issues that remain to be studied include the efficiency of conversion of carotenoids in whole foods to vitamin A by using a variety of foods in various field settings and whether intraluminal factors (eg, parasitism) and vitamin A status affect this conversion. In addition, the biological activity of carotenoid metabolites should be better understood, particularly their effects on retinoid signaling.

Nutritional Potential of Red Palm Oil for Combating Vitamin A Deficiency

Although the severe vitamin A deficiency responsible for ocular damage is now rare, subclinical vitamin A deficiency still contributes importantly to high child mortality in the developing countries of Asia. This demands urgent and effective preventive action. Although periodic large doses of vitamin A for this purpose have been a favoured approach of international agencies, the coverage achieved has been inadequate and is usually not sustainable without external support. for this reason, there has been increasing emphasis on a sustainable dietary approach to the prevention of subclinical vitamin A deficiency. One part of this can be the production and use of red palm oil as a salad and cooking oil or blended into other vegetable cooking oils. the latter will also improve the caloric density of the diets, a serious limiting factor for young children in the region. It will also add antioxidant activity to the diet.

Vitamin A deficiency in healthy children aged 6-59 months in Izmir Province of Turkey.

Vitamin A deficiency even at subclinical levels is associated with increased childhood mortality. There have been few studies related to vitamin A status of children in Turkey. The aim of this study was to assess vitamin A status of children aged 6-59 months in Izmir, Turkey, and to evaluate the relationship of these levels with nutritional status. One hundred and sixty children were selected for the study using the cluster sampling method. Serum retinol levels were measured by high-performance liquid chromatography (HPLC) and ranged from 9.8 to 59.2 micrograms/dL (mean 29.3 +/- 9.5 micrograms/dL). Levels were below the lower limit of the normal range in 15.6% of the children. Deficient and marginal serum retinol among stunted children were observed in 16% and 42% respectively. There was a statistically significant relationship between low serum retinol and stunting (P < 0.05). Although xerophthalmia and other clinical signs of vitamin A deficiency are rarely seen, subclinical vitamin A deficiency is a public health problem in Izmir, Turkey.