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Sunday, May 16, 2010

Most Americans Vitamin D Deficient

Most Americans are vitamin D deficient.

There appears to be some limited data suggesting that full-spectrum light bulbs might improve vitamin D levels. However the effect, as discussed in the study from a Canadian government council, appears to be small. Perhaps technology has improved since this study (which spans the years 1945-1993), so maybe exposure to such indoor light might have some role in boosting vitamin D. But the only way to know for sure is to get your blood tested.

Full-Spectrum Fluorescent Lighting Effects on People: A Critical Review
Jennifer A. Veitch, Ph.D. and Shelley L. McColl
National Research Council of Canada / Institute for Research in Construction

Full-spectrum fluorescent lighting has been credited with causing dramatic improvements in a wide variety of behaviours, mental health outcomes, and physical health effects. These effects include reduction in dental caries, improved classroom behaviour in schoolchildren, enhanced academic achievement, more efficient visual performance, more attractive appearance of both people and spaces, and improved mood in cases of seasonal depression. Popular media reports have tended to emphasize studies that have demonstrated differences in outcomes as a function of light source spectral power distribution. However, the scientific literature also includes reports with null and contradictory effects. This comprehensive review covers the period 1945-1993 and includes a critical appraisal of the methodology in each study. The studies are grouped according to their dependent variables under the broad headings "Behaviour and Performance", "Mental Well-Being and Affect", and "Physiology and Health". In general, the quality of the research is poor, making it difficult to determine whether or not treatment effects may legitimately be attributed to light source spectral power distribution. A few rigorous investigations of full-spectrum fluorescent lighting have demonstrated small effects; however, few researchers have taken up the challenge to replicate their work. These small effects do not support the claims that full-spectrum fluorescent lighting will produce better performance, mood, or health in the general population. More fruitful avenues for future research include investigations of other lighting parameters including intensity, variability, and flicker and an emphasis on the possibility that individual differences exist in sensitivity to the spectral composition of light sources. The role of mental processes -- for example, beliefs, memories, and expectations -- in mediating the effects of lighting on behaviour stands out as most promising for future research.


4.2.4 Summary. There is little research evidence to support the contention that full-spectrum fluorescent lighting affects physical health. The literature reviewed here is, generally speaking, poor in quality. The only process in which important effects may exist is in the metabolism of Vitamin D and, indirectly, on calcium absorption and dental caries. However, even in this instance the best outcomes may relate as much to the intensity of light (e.g., Neer et al., 1971) or to some other unknown aspect of illumination (e.g., Feller et al., 1974). Some evidence suggests that a lack of natural daylight can cause changes in seasonal patterns of cortisol secretion (Kuller & Lindsten, 1992), although the meaning of this finding is unknown. In the absence of data that show overall lamp type effects on health, growth, or development, claims that any such effects exist are premature.


veghunter said...

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Keep up the great work!

paul said...

Vitamin D deficiency may lead to certain health problems. Take enough of that vitamin to maintain your health.

Lorna Vanderhaeghe