Vitamin D deficiency: a worldwide problem with health consequences

Vitamin D deficiency is now recognized as a pandemic. The major cause of vitamin D deficiency is the lack of appreciation that sun exposure in moderation is the major source of vitamin D for most humans. Very few foods naturally contain vitamin D, and foods that are fortified with vitamin D are often inadequate to satisfy either a child's or an adult's vitamin D requirement. Vitamin D deficiency causes rickets in children and will precipitate and exacerbate osteopenia, osteoporosis, and fractures in adults. Vitamin D deficiency has been associated with increased risk of common cancers, autoimmune diseases, hypertension, and infectious diseases. A circulating level of 25-hydroxyvitamin D of >75 nmol/L, or 30 ng/mL, is required to maximize vitamin D's beneficial effects for health. In the absence of adequate sun exposure, at least 800-1000 IU vitamin D3/d may be needed to achieve this in children and adults. Vitamin D2 may be equally effective for maintaining circulating concentrations of 25-hydroxyvitamin D when given in physiologic concentrations.     

Vitamin A deficiency in Bangladesh

Vitamin A deficiency is a major problem in Bangladesh, accountingfor something like 30 000 children under sixyears of age goingblind each year, and at least half of these dying within weeksof the blinding episode National studies have confirmed widespreadlow intakes of vitamin A in the diet and high prevalences ofsigns and symptoms of xerophthalmia. These prevalences are allwell in excess of WHO threshold levels at which a major publichealth problem is considered to exist. Smaller, often clinically-basedstudies have confirmed low serum retinol levels and interactionswith diarrhoea, measles and other infectious disease includingthe presence of enteric parasites. Risk factors in the developmentof xerophthalmia include diet, age, infectious disease, maternaleducation, socioeconomicstatus seasonal variation and geographicclustering. Although short to long term prevention and controlprogrammes are to some extent in place, much remains to be done.     

Single nutrient deficiency and cell-mediated immune responses. III. Vitamin A

Weanling rats were fed vitamin-A deficient diet for 3–4 weeks until the weight plateaued. The weight of the thymus and the spleen and the number of mononuclear cells contained in these lymphoid organs were similar in vitamin A-deficient animals and pair-fed controls. Lymphocyte stimulation response to phytohemagglutinin and antibody plaque forming cell number were decreased. Serum thymine hormone activity in the vitamin A-deficient group and pair-fed controls was comparable. These data confirm the important role of vitamin A in modulating cell-mediated immunity.     

Vitamin B-complex deficiency and visual acuity.

1. A study was carried out on 973 school children to find out any relationship between vitamin B-complex deficiency signs and defective vision, and the effect of supplementation of B-complex vitamins on visual acuity. 2. The results of the study showed a significant association between presence of clinical signs of vitamin B-complex deficiency and defective vision. 3. Supplementation with vitamin B-complex was found to have a beneficial effect in improving the visual-acuity status of defective children and in preventing visual defects from developing. 4. It is concluded, therefore, that from the present study it appears that the relationship between vitamin B-complex deficiency and visual defects could be one of 'cause and effect'.     

Vitamin A deficiency and attributable mortality among under-5-year-olds.

Reported are estimates of the prevalence in developing countries of physiologically significant vitamin A deficiency and the number of attributable deaths. The WHO classification of countries by the severity and extent of xerophthalmia was used to categorize developing countries by likely risk of subclinical vitamin A deficiency. Using vital statistics compiled by UNICEF, we derived population figures and mortality rates for under-5-year-olds. The findings of vitamin A supplementation trials were applied to populations at-risk of endemic vitamin A deficiency to estimate the potential impact of improved vitamin A nutriture in reducing mortality during preschool years. Worldwide, over 124 million children are estimated to be vitamin A deficient. Improved vitamin A nutriture would be expected to prevent approximately 1-2 million deaths annually among children aged 1-4 years. An additional 0.25-0.5 million deaths may be averted if improved vitamin A nutriture can be achieved during the latter half of infancy. Improved vitamin A nutriture alone could prevent 1.3-2.5 million of the nearly 8 million late infancy and preschool-age child deaths that occur each year in the highest-risk developing countries.     

Vitamin A deficiency in southern Ethiopia

In Arsi and Bale regions of Ethiopia we found an area in which vitamin A deficiency is hyperendemic and linked to monocrop grain farming. The prevalence of mild xerophthalmia is higher in villages than settlements and higher in settlements than towns (p less than 0.001 for both). The prevalence of mild xerophthalmia is higher in males than females (p = 0.03) and the difference cannot be explained by ecological factors. Nutritional status, length of weaning, severe diseases, and intake of food with low-vitamin A content are factors associated with vitamin A deficiency. Length of weaning and severe diseases play a more important role than nutritional status in this study. The prevalence of diarrhea and respiratory diseases was twice as high in children with xerophthalmia than in children without (p less than 0.001 and less than 0.02, respectively). The incidence of measles was higher in children with vitamin A deficiency than in children without, relative risk 4.7 (p = 0.01).     

Vitamin B6 deficiency in uremia.

Significant decreases in plasma pyridoxal-5-phosphate (PLP), plasma glutamic-oxaloacetic transaminase (PGOT) and erythrocyte glutamic-oxaloacetic transaminase (EGOT) were found in 29 uremic patients including 14 who had been on hemodialysis an average of 15.8 months. The mean PLP values of the uremic patients (5.39 +/- 0.37 ng/ml) were clearly lower than the values obtained for the normal group (9.30 +/- 0.80 mg/ml). The mean PGOT values of the uremic patients (dialyzed 4.07 +/- 0.29 U/liter, undialyzed 5.31 +/- 0.49 U/liter) were significantly lower than the normal group (6.57 +/- 0.39 U/liter). The mean EGOT value of the uremic patients (325 +/- 17 U/liter) was also lower than normal subjects (416 +/-21 U/liter). Stimulation of the EGOT by exogenous PLP (EGOT index) was less in dialyzed patients (1.60) than normal subjects (1.80) while the undialyzed uremic subjects had a greater than normal stimulation (2.12). All of these results indicate that uremic patients are vitamin B6 deficient and that those undergoing hemodialysis may have decreased amounts of the EGOT apoenzyme.     

Vitamin A deficiency,iron deficiency,and anemia among preschool children in the Republic of the Marshall Islands

OBJECTIVE: We investigated the co-occurrence of vitamin A deficiency, iron deficiency, and anemia among young children in the Republic of the Marshall Islands. METHODS: Hemoglobin, serum retinol, and serum ferritin were assessed in the Republic of the Marshall Islands Vitamin A Deficiency Study, a community-based survey that involved 919 children ages 1 to 5 y. RESULTS: The proportion of children with vitamin A deficiency (serum retinol concentrations < 0.70 microM/L) was 59.9%. The prevalences of anemia (hemoglobin < 110 g/L), iron deficiency (serum ferritin < 12 microg/L), and iron deficiency anemia (iron deficiency and anemia) were 36.4%, 53.5%, and 23.8%, respectively. The proportion of children who had co-occurrence of vitamin A and iron deficiencies was 33.2%. The mean ages of children with and without vitamin A deficiency were 3.2 +/- 1.4 and 2.9 +/- 1.5 y, respectively (P = 0.01), and the mean ages of those with and without iron deficiency were 2.7 +/- 1.3 and 3.5 +/- 1.4 y, respectively (P < 0.0001).CONCLUSIONS: Children in the Republic of the Marshall Islands, ages 1 to 5 y, are at high risk of anemia, vitamin A deficiency, and iron deficiency, and one-third of these children had the co-occurrence of vitamin A and iron deficiencies. Further investigation is needed to identify risk factors and evaluate interventions to address vitamin A and iron deficiencies among children.     

维生素A缺乏对大鼠铁水平及Hepcidin、FP1与DMT1 mRNA表达的影响

目的研究维生素A(VA)缺乏时大鼠铁营养状况的变化,从分子水平探讨VA缺乏对大鼠铁代谢的影响。方法 16只成年健康雄性SD大鼠,随机分为对照组(Con)和VA缺乏组(-VA),每组8只,分别饲以正常饲料和VA缺乏饲料。连续喂养4周,脱椎处死,取血及肝、脾组织检测血红蛋白(Hb)含量、血清铁(SI)、血清铁蛋白(SF)及肝、脾组织铁含量。以β-actin为内参,半定量RT-PCR技术比较两组大鼠铁调素(Hepcidin)、膜铁转运蛋白1(FP1)和二价金属离子转运蛋白(DMT1)肝组织mRNA的表达水平。结果 VA缺乏组SI、SF和Hb显著低于对照组(P0.05),肝、脾铁含量显著高于对照组(P0.05);Hepcidin及DMT1mRNA在肝组织中表达水平显著增加(P0.05)。结论 VA缺乏致使Hepcidin表达水平的升高,导致肝、脾铁储量增加而机体循环铁量和铁营养水平下降。