If you are a person of a "seasoned" age, you might want to pay attention to your vitamin D level. Low blood levels of vitamin D may be linked to a greater risk of dying in older adults, especially among those who are frail.

Researchers at Oregon State University, led by Ellen Smit, used data from the Third National Health and Nutrition Examination Survey (NHANES III) to examine over 4,300 adults aged 60 and older. The study divided the participants into four groups. Those in the lowest group had blood levels less than 50 nanograms per milliliter of vitamin D in their blood [measured as serum 25 (OH)D], and the highest group had a vitamin D level of 84 or better.

Older adults should attempt to get outside activity more often because sunlight exposure produces vitamin D in the body.

People with the lowest blood levels of vitamin D tended to be more frail. However, the researchers acknowledged that because of the cross-sectional nature of the study, it could not be determined if low vitamin D contributed to fragility or whether those who were frail became deficient in vitamin D due to health problems.

Smit, who is a nutritional epidemiologist at OSU's College of Public health and Human Sciences, said that it may not matter which came first because vitamin D impacts muscle function and bone health, so low vitamin D levels make an older person worse off and at greater risk of dying than older people who are frail and are not vitamin D deficient.

In an OSU press release, Smit said, "What this really means is that it is important to assess vitamin D levels in older adults, and especially among people who are frail."

According to the American Academy of Physical Medicine and Rehabilitation, frailty occurs when three or more of the following conditions are met: weight loss of greater than 5 percent in the last year; exhaustion; decreased grip strength; slow walking; and decreased physical activity. Pre-frailty is when less than three of these characteristics occur.

"Our study suggests that there is an opportunity for intervention with those who are in the pre-frail group, but could live longer, independent lives if they get proper nutrition and exercise," said Smit in the OSU press release. Older adults should attempt to get outside activity more often because sunlight exposure produces vitamin D in the body.

Not many foods contain vitamin D naturally, but the flesh of fatty fish such as mackerel, salmon, and tuna are good sources of the vitamin. Small amounts are found in beef liver, egg yolks, and cheese. Most of the vitamin D in the American diet is supplied by fortified foods like milk and some brands of ready-to-eat breakfast cereals, orange juice, yogurt, margarine and other food products.

It is estimated that about 70 percent of Americans are deficient in vitamin D. The Linus Pauling Institute at OSU recommends that adults take 2,000 IU of supplemental vitamin D per day. Currently, the Recommended Dietary Allowance for vitamin D for adults over the age of 60 is 600 IU per day.

The study was published online in the European Journal of Clinical Nutrition.