Critique of the considerations for establishing the tolerable upper intake level for vitamin D: critical need for revision upwards.

Department of Nutritional Sciences, University of Toronto, Mount Sinai Hospital, Toronto, M5G 1L5, Canada.
Journal of Nutrition (Impact Factor: 4.23). 04/2006; 136(4):1117-22.
Source: PubMed

ABSTRACT The tolerable upper intake level (UL) for vitamin D is 50 mcg/d (2000 iu/d) in North America and in Europe. In the United Kingdom a guidance level exists for vitamin D, 25 mcg/d (1000 iu/d), defined as the dose "of vitamins and minerals that potentially susceptible individuals could take daily on a life-long basis, without medical supervision in reasonable safety." Exposure of skin to sunshine can safely provide an adult with vitamin D in an amount equivalent to an oral dose of 250 mcg/d. The incremental consumption of 1 mcg/d of vitamin D3 raises serum 25-hydroxyvitamin D [25(OH)D ] by approximately 1 nmol/L (0.4 microg/L). Published reports suggest toxicity may occur with 25(OH)D concentrations beyond 500 nmol/L (200 microg/L). Older adults are advised to maintain serum 25(OH)D concentrations >75 nmol/L. The preceding numbers indicate that vitamin D3 intake at the UL raises 25(OH)D by approximately 50 nmol/L and that this may be more desirable than harmful. The past decade has produced separate North American, European, and U.K. reports that address UL or guidance-level values for vitamin D. Despite similar well-defined models for risk assessment, each report has failed to adapt its message to new evidence of no adverse effects at higher doses. Inappropriately low UL values, or guidance values, for vitamin D have hindered objective clinical research on vitamin D nutrition, they have hindered our understanding of its role in disease prevention, and restricted the amount of vitamin D in multivitamins and foods to doses too low to benefit public health.

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    ABSTRACT: Unlike vitamin D recommendations by the Institute of Medicine, the Clinical Practice Guidelines by the Endocrine Society acknowledge body weight differentials and recommend obese subjects be given two to three times more vitamin D to satisfy their body's vitamin D requirement. However, the Endocrine Society also acknowledges that there are no good studies that clearly justify this. In this study we examined the combined effect of vitamin D supplementation and body weight on serum 25-hydroxyvitamin (25(OH)D) and serum calcium in healthy volunteers. We analyzed 22,214 recordings of vitamin D supplement use and serum 25(OH)D from 17,614 healthy adult volunteers participating in a preventive health program. This program encourages the use of vitamin D supplementation and monitors its use and serum 25(OH)D and serum calcium levels. Participants reported vitamin D supplementation ranging from 0 to 55,000 IU per day and had serum 25(OH)D levels ranging from 10.1 to 394 nmol/L. The dose response relationship between vitamin D supplementation and serum 25(OH)D followed an exponential curve. On average, serum 25(OH)D increased by 12.0 nmol/L per 1,000 IU in the supplementation interval of 0 to 1,000 IU per day and by 1.1 nmol/L per 1,000 IU in the supplementation interval of 15,000 to 20,000 IU per day. BMI, relative to absolute body weight, was found to be the better determinant of 25(OH)D. Relative to normal weight subjects, obese and overweight participants had serum 25(OH)D that were on average 19.8 nmol/L and 8.0 nmol/L lower, respectively (P<0.001). We did not observe any increase in the risk for hypercalcemia with increasing vitamin D supplementation. We recommend vitamin D supplementation be 2 to 3 times higher for obese subjects and 1.5 times higher for overweight subjects relative to normal weight subjects. This observational study provides body weight specific recommendations to achieve 25(OH)D targets.
    PLoS ONE 11/2014; 9(11):e111265. · 3.53 Impact Factor
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    ABSTRACT: In recent years, there have been reports suggesting a high prevalence of low vitamin D intakes and vitamin D deficiency or inadequate vitamin D status in Europe. Coupled with growing concern about the health risks associated with low vitamin D status, this has resulted in increased interest in the topic of vitamin D from healthcare professionals, the media and the public. Adequate vitamin D status has a key role in skeletal health. Prevention of the well-described vitamin D deficiency disorders of rickets and osteomalacia are clearly important, but there may also be an implication of low vitamin D status in bone loss, muscle weakness and falls and fragility fractures in older people, and these are highly significant public health issues in terms of morbidity, quality of life and costs to health services in Europe.Although there is no agreement on optimal plasma levels of vitamin D, it is apparent that blood 25-hydroxyvitamin D [25(OH)D] levels are often below recommended ranges for the general population and are particularly low in some subgroups of the population, such as those in institutions or who are housebound and non-Western immigrants. Reported estimates of vitamin D status within different European countries show large variation. However, comparison of studies across Europe is limited by their use of different methodologies. The prevalence of vitamin D deficiency [often defined as plasma 25(OH)D <25 nmol/l] may be more common in populations with a higher proportion of at-risk groups, and/or that have low consumption of foods rich in vitamin D (naturally rich or fortified) and low use of vitamin D supplements.The definition of an adequate or optimal vitamin D status is key in determining recommendations for a vitamin D intake that will enable satisfactory status to be maintained all year round, including the winter months. In most European countries, there seems to be a shortfall in achieving current vitamin D recommendations. An exception is Finland, where dietary survey data indicate that recent national policies that include fortification and supplementation, coupled with a high habitual intake of oil-rich fish, have resulted in an increase in vitamin D intakes, but this may not be a suitable strategy for all European populations. The ongoing standardisation of measurements in vitamin D research will facilitate a stronger evidence base on which policies can be determined. These policies may include promotion of dietary recommendations, food fortification, vitamin D supplementation and judicious sun exposure, but should take into account national, cultural and dietary habits. For European nations with supplementation policies, it is important that relevant parties ensure satisfactory uptake of these particularly in the most vulnerable groups of the population.
    Nutrition Bulletin 10/2014; 39(4).
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    ABSTRACT: Vitamin D is unique among the essential nutrients in that it can be made in the body via exposure of the skin to sunlight. There are few rich sources of vitamin D in the diet. Vitamin D is essential for maintaining healthy bones and deficiency of vitamin D causes rickets in children and osteomalacia in adults. In the UK, there is evidence that low vitamin D status is prevalent in the population and older adults living in institutions are particularly at risk.There are two forms of vitamin D that can be added to foods and drinks: vitamin D2 and D3. They have somewhat different structures, and there are some differences in the way they are metabolised by the body. Overall, the evidence for the relative effectiveness of vitamin D2 vs. D3 is mixed, and more studies are needed to provide a clearer picture. However, there does seem to be some indication that D3 is more effective than D2 in raising vitamin D status.
    Nutrition Bulletin 09/2011; 36(3).


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