Two recent studies - one from Oregon State University and another from the University of Maryland's School of Medicine - have determined that lower blood levels of the "sunshine vitamin" - vitamin D (serum 25-hydroxyvitamin D (25(OH)D)) - equates to earlier death and greater incidence of frailty later in life.
The most recent study, led by Dr. Ellen Smit, an assistant professor at Oregon State, analyzed 4,731 adults over the age of 60 years old. The study followed the adults for twelve years using data from the Third National Health and Nutrition Examination Survey.
The researchers measured the adults' levels of frailty, gauged by low body mass, exhaustion, general weakness, slower walking and reduced physical activity.
The randomized study's methodology, intended to represent the general U.S. elderly population, also followed death rates and correlated them with serum vitamin D levels.
Their results found that those adults with vitamin D levels in the lowest quarter percentile had nearly twice the rate of frailty than those with vitamin D levels in the highest quarter percentile. This lowest group had vitamin D levels significantly lower than 50 nanograms of 25(OH)D per milliliter of blood. This level is consider by many vitamin D experts to be the minimum healthy level of serum vitamin D.
The group with the highest quarter percentile levels of vitamin D had levels of 84 nanograms 25(OH)D per milliliter or higher.
Dr. Smit pointed out that the results indicate elderly adults should be aware of their vitamin D levels. "What this really means is that it is important to assess vitamin D levels in older adults, and especially among people who are frail," she said.
It terms of mortality, those adults who were frail with low vitamin D levels were three times more likely to die early than adults with higher vitamin D levels with less frailty.
These results matched a study published earlier in 2012 from researchers at the University of Maryland's School of Medicine. This study followed 1,155 Italian adults who were 65 and older.
In this Italian study, the average serum 25(OH)D level was 16 ng/mL among the whole group. The researchers found that adults with levels lower than 20 ng/mL had a 9% greater likelihood of earlier death, and each 5 ng/mL reduction in serum vitamin D resulted in a 46% increase in the risk of early death.
The Italian study also qualified what was considered a "prefrailty" state, gauged by slowing activity and lower vitamin D levels.
While vitamin D is not found in many foods, ultraviolet-B radiation stimulates the body's own production of vitamin D with little effort other than exposing the skin to the sun at the right time of day in the right location. Locations below about 42-degrees latitude offer UV-B radiation levels high enough to stimulate D production. Locations above 42-degrees latitude result in little vitamin D production. Vitamin D3 supplements are thus recommended for those with poor sun exposure and/or those who live north of 42-degrees latitude.
- Smit E, Crespo CJ, Michael Y, Ramirez-Marrero FA, Brodowicz GR, Bartlett S, Andersen RE. The effect of vitamin D and frailty on mortality among non-institutionalized US older adults. Eur J Clin Nutr. 2012 Jun 13.
- Shardell M, D'Adamo C, Alley DE, Miller RR, Hicks GE, Milaneschi Y, Semba RD, Cherubini A, Bandinelli S, Ferrucci L. Serum 25-hydroxyvitamin D, transitions between frailty states, and mortality in older adults: the Invecchiare in Chianti Study. J Am Geriatr Soc. 2012 Feb;60(2):256-64.
- Adams C. Healthy Sun: Healing with Sunshine and the Myths About Skin Cancer. Logical Books, 2011.