A population of adults in Hawaii who averaged about 29 hours a week of sun exposure still mostly did not have an optimal amount of vitamin D in their blood.
Participants: The study population consisted of 93 adults (30 women and 63 men) with a mean (SEM) age and body mass index of 24.0 yr (0.7) and 23.6 kg/m2 (0.4), respectively. Their self-reported sun exposure was 28.9 (1.5) h/wk, yielding a calculated sun exposure index of 11.1 (0.7).
Main Outcome Measures: Serum 25(OH)D concentration was measured using a precise HPLC assay. Low vitamin D status was defined as a circulating 25(OH)D concentration less than 30 ng/ml.
Results: Mean serum 25(OH)D concentration was 31.6 ng/ml. Using a cutpoint of 30 ng/ml, 51% of this population had low vitamin D status. The highest 25(OH)D concentration was 62 ng/ml.
I wonder what their racial and age breakdown was. First off, darker skinned people will make less vitamin D from a given amount of sun exposure. Second, as skin ages it very likely becomes less efficient at harnessing sun to make vitamin D.
Another report on this study says only about 22 of those hours were without sunscreen on average. But 22 hours a week is a lot more than people get in colder climates except maybe during the summer times.
Another recent study by Paul Lips and colleagues using subjects from the Longitudinal Aging Study Amsterdam found that blood vitamin D below 20 ng/ml was associated with a more rapid decline in physical performance among the elderly.
Conclusions: Serum 25-OHD concentrations below 20 ng/ml are associated with poorer physical performance and a greater decline in physical performance in older men and women. Because almost 50% of the population had serum 25-OHD below 20 ng/ml, public health strategies should be aimed at this group.
This doesn't prove a cause and effect. It could be that sicker people get out into the sun less. Or people who get out more exercise more and therefore do a better job of maintaining muscle mass as they age.
Another study from 2005 found that even women receiving anti-osteoporosis therapy do not have enough vitamin D.
Conclusions: More than half of North American women receiving therapy to treat or prevent osteoporosis have vitamin D inadequacy, underscoring the need for improved physician and public education regarding optimization of vitamin D status in this population.
Think about what this says about doctors. These women have crumbling bones. Did the doctors prescribe vitamin D to boost their deficient blood vitamin D levels? Probably not. Yet vitamin D is essential for good bone health.
|Share |||Randall Parker, 2007 July 01 05:49 PM Aging Diet Studies|