Prevalence of vitamin D insufficiency in Brazilian adolescents.

BACKGROUND/AIMS: Cutaneous sun exposure and dietary vitamin D intake are important determinants of vitamin D status. The objective of the present study was to evaluate the vitamin D status of a group of healthy adolescent students living in Brazil. METHODS: One hundred and thirty-six adolescents, 64 boys and 72 girls, aged 16-20 years old, living in a rural town in the state of São Paulo, Brazil, participated in this study. RESULTS: The mean dietary vitamin D intake was 140 (120-156) IU/day [3.5 (3.0-3.9) microg/day]. Only 14.9% of the students met the daily adequate intake recommendation of vitamin D. Only 27.9% practice physical activity outdoors and 17.6% of the adolescents apply sunscreen daily. The mean 25(OH)D concentration was 73.0 (22.0) nmol/l [29.2 (8.8) ng/ml]. Vitamin D insufficiency was observed in 60% of adolescents. CONCLUSIONS: The present study suggests that even in a sunny climate like Brazil the prevalence of vitamin D insufficiency in adolescents is high. Most likely this is due to low intakes of vitamin D in this group. Due to the limited extent of natural dietary sources of vitamin D, a policy of vitamin D food fortification should be considered in the future, and in the meantime greater use of vitamin D supplements in this population group should be encouraged to provide the increased amounts of this essential nutrient for optimal health.

Vitamin D supplementation during Antarctic winter.

BACKGROUND: Persons with limited exposure to ultraviolet B light, including space travelers, may not receive enough vitamin D. Recent studies indicate that optimal serum 25-hydroxyvitamin D [25(OH)D] should be > or = 80 nmol/L. OBJECTIVE: This study was designed to evaluate the effectiveness of 3 doses of vitamin D to raise and maintain 25(OH)D to a concentration >80 nmol/L in persons with limited ultraviolet B light exposure. DESIGN: This was a 5-mo, prospective, randomized, double-blind study of vitamin D supplementation. It was conducted during winter in Antarctica at the McMurdo Station, when ultraviolet B radiation levels are essentially zero. The 55 subjects were randomly divided into 3 groups for vitamin D supplementation: 2000 IU/d (n = 18), 1000 IU/d (n = 19), and 400 IU/d (n = 18). An additional 7 subjects did not take supplements or took supplements of their own choosing. Blood samples were collected about every 2 mo during the winter. RESULTS: About 5 mo after supplementation started, 25(OH)D increased to 71 +/- 23 nmol/L in the 2000-IU/d group, 63 +/- 25 nmol/L in the 1000-IU/d group, and 57 +/- 15 nmol/L in the 400-IU/d group and decreased to 34 +/- 12 nmol/L in the group not taking supplements. CONCLUSIONS: These data will enable us to provide space crews with evidence-based recommendations for vitamin D supplementation. The findings also have implications for other persons with limited ultraviolet light exposure, including polar workers and the elderly.

Vitamin D requirement and setting recommendation levels - current Nordic view.

At the latitude of the Nordic countries, where there is almost no dermal formation of vitamin D during winter, dietary intake is required to avoid deficiency. Dietary intake is of the order of 4-5 microg/day but varies widely. The lowest intake is seen among adolescents. Low levels of serum 25(OH)D have been found in population groups in all Nordic countries. The drop in 25(OH)D during the winter months may be considerable, falling below acceptable levels (50 nmol/L) in one half of the population. To ensure an acceptable vitamin D status is maintained in the population and to diminish the seasonal drop in 25(OH)D, the Nordic Nutrition Recommendations 2004 increased the vitamin D recommendation for the age group 2-60 years by 50% from 5 microg/day to 7.5 microg/day. To attain such an intake at the population level, public health actions, including information dissemination and increased fortification of foods, are necessary.

Vitamin D requirement and setting recommendation levels: long-term perspectives.

Target intakes of vitamin D to prevent rickets and osteomalacia are difficult to estimate because of the dual sources of vitamin D with dermal production and absorption from the intestine. However, vitamin D deficiency is associated with other diseases, e.g., myopathy, falls, fractures, autoimmune disorders, cardiovascular diseases, and malignancies, which underlines the necessity of redefining recommendations. A plasma level of 25-hydroxyvitamin D (25OHD) <50 nmol/L increases the risk of secondary hyperparathyroidism, whereas levels between 75 and 100 nmol/L appear optimal for maintaining general health. In adults, a minimum dietary intake of 17.5-25 microg/day is necessary to achieve these levels. Perspectives of future research are outlined here.

Overview of the conference "Vitamin D and Health in the 21st Century: an Update".

We summarize the key findings, strength of the evidence, and research needs identified in the National Institutes of Health conference "Vitamin D and Health in the 21st Century: an Update," which was held in September 2007; a systematic evidence-based review; and a National Institutes of Health roundtable discussion held after the conference by scientists with relevant expertise. The evidence-based review addressed 5 questions on 25-hydroxyvitamin D [25(OH)D] and functional outcomes across the life cycle and response to exposure, bone health outcomes of supplementation, risks and benefits of sun exposure, and adverse outcomes. These questions also framed the conference and roundtable discussions. Researchers have made considerable progress in understanding the relation of 25(OH)D to bone health outcomes in the elderly and in postmenopausal women, but we know less about its impact on other stages of the life cycle and in racial and ethnic groups. Limitations of the existing data include the failure of many studies to control for important confounders [baseline 25(OH)D concentration, skin pigmentation, body mass index, compliance, etc], sparse data on key vulnerable populations (dark-skinned persons, reproducing women, infants, children, and adolescents), problems of accuracy and excessive variability in measuring 25(OH)D, lack of established relation of 25(OH)D with functional outcomes except in the elderly, and limited information on the effects of vitamin D independent of calcium, magnesium, and phosphate. Future research should determine and validate across the life cycle relevant functional outcomes for bone and other health factors as well as adverse outcomes for the biomarker of exposure, 25(OH)D, to enable assessment of the role of vitamin D status in health maintenance and disease prevention.

Should we be concerned about the vitamin D status of athletes?

A surprisingly high prevalence of vitamin D insufficiency and deficiency has recently been reported worldwide. Although very little is known about vitamin D status among athletes, a few studies suggest that poor vitamin D status is also a problem in athletic populations. It is well recognized that vitamin D is necessary for optimal bone health, but emerging evidence is finding that vitamin D deficiency increases the risk of autoimmune diseases and nonskeletal chronic diseases and can also have a profound effect on human immunity, inflammation, and muscle function (in the elderly). Thus, it is likely that compromised vitamin D status can affect an athlete's overall health and ability to train (i.e., by affecting bone health, innate immunity, and exercise-related immunity and inflammation). Although further research in this area is needed, it is important that sports nutritionists assess vitamin D (as well as calcium) intake and make appropriate recommendations that will help athletes achieve adequate vitamin D status: serum 25(OH)D of at least 75 or 80 nmol/L. These recommendations can include regular safe sun exposure (twice a week between the hours of 10 a.m. and 3 p.m. on the arms and legs for 5-30 min, depending on season, latitude, and skin pigmentation) or dietary supplementation with 1,000-2,000 IU vitamin D3 per day. Although this is significantly higher than what is currently considered the adequate intake, recent research demonstrates these levels to be safe and possibly necessary to maintain adequate 25(OH)D concentrations.

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 d and rehabilitation: improving functional outcomes.

Vitamin D inadequacy is pandemic among rehabilitation patients in both inpatient and outpatient settings. Male and female patients of all ages and ethnic backgrounds are affected. Vitamin D deficiency causes osteopenia, precipitates and exacerbates osteoporosis, causes the painful bone disease osteomalacia, and worsens proximal muscle strength and postural sway. Vitamin D inadequacy can be prevented by sensible sun exposure and adequate dietary intake with supplementation. Vitamin D status is determined by measurement of serum 25-hydroxyvitamin D. The recommended healthful serum level is between 30 and 60 ng/mL. 25-Hydroxyvitamin D levels of >30 ng/mL are sufficient to suppress parathyroid hormone production and to maximize the efficiency of dietary calcium absorption from the small intestine. This can be accomplished by ingesting 1000 IU of vitamin D(3) per day, or by taking 50,000 IU of vitamin D(2) every 2 weeks. Vitamin D toxicity is observed when 25-hydroxyvitamin D levels exceed 150 ng/mL. Identification and treatment of vitamin D deficiency reduces the risk of vertebral and nonvertebral fractures by improving bone health and musculoskeletal function. Vitamin D deficiency and osteomalacia should be considered in the differential diagnosis of patients with musculoskeletal pain, fibromyalgia, chronic fatigue syndrome, or myositis. There is a need for better education of health professionals and the general public regarding the optimization of vitamin D status in the care of rehabilitation patients.