What’s better for your vitamin D? Sunshine or supplements? Read these studies and find out:


Vitamin D Status and Its Adequacy in Healthy Danish Perimenopausal Women: Relationships to Dietary Intake, Sun Exposure and Serum Parathyroid Hormone (2001)

Conclusion: 2.5 year-long study of 2,016 healthy, white menopausal women in Denmark concludes that menopausal women who avoid summer sun exposure and do not supplement with vitamin D are prone to vitamin D insufficiency. Those who intentionally exposed themselves to regular sun exposure had the highest levels, those who reported occasional sun exposure had lower levels, and those reported actively avoiding sun exposure had the lowest levels. Active sunbathing was correlated more highly with vitamin D status than supplementation.The study also found that their vitamin D levels spiked significantly in the summer.


Ultraviolet Irradiation Corrects Vitamin D Deficiency and Suppresses Secondary Hyperparathyroidism in the Elderly (1998)

Conclusion: 45 elderly, female nursing home patients were enrolled in a 3-month randomized clinical trial where they either received (1) an extremely mild dose of UVB exposure three times per week, (2) 400 IU of oral vitamin D3 per day (very, very small dose), or (3) no treatment at all. At the beginning of the study 95% of patients were clinically deficient in vitamin D (with 60% being severely deficient), after the three months of treatment the UVB and oral vitamin D groups both enjoyed a doubling of their vitamin D levels. Although their vitamin D levels were still insufficient, the level increase is still impressive considering how small the dose of UVB and vitamin D they were being given. The researchers concluded that UVB exposure and oral vitamin D are basically equally effective for raising and maintaining vitamin D levels. The control group receiving no treatment demonstrated zero changes in their vitamin D levels.


Human Plasma Transport of Vitamin D after Its Endogenous Synthesis (1993)

Conclusion: This study involving 10 subjects compared the plasma vitamin D increasing effects of UV exposure and oral vitamin D2 supplementation. Although an oral dose of 50,000 IU of vitamin D2 resulted in a much faster plasma vitamin D increase starting at just 4 hours after the dose, this increase began to drop rapidly and the vitamin D levels of the subjects returned to baseline after just two days. Plasma vitamin D level increases from UV exposure, on the other hand, took 10 hours to start, peaked at 24 hours, only began dropping at three days, and did not return to baseline until after seven days. This study proves that for a longer-lasting vitamin D boost, sunshine is far superior to oral vitamin D2. This study did not, however, test the effectiveness of vitamin D3, which has been found in many studies to be more effective than D2 for increasing plasma vitamin D levels.


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