Doctors and scientists alike have long touted the many benefits of vitamin D, the "sunshine vitamin" that could help prolong a person's life by preventing heart disease, diabetes, cancer, allergies and mental illness. However, a new study has revealed just the opposite after it linked low levels of vitamin D to longevity.

"We found that familial longevity was associated with lower levels of vitamin D and a lower frequency of allelic variation in the CYP2R1 gene, which was associated with higher levels of vitamin D," Dr. Diana van Heemst, Department of Gerontology and Geriatrics, Leiden University Medical Center, Leiden, the Netherlands, and her team wrote in the study.

The latest findings, published in the Canadian Medical Association Journal, cast doubt on previous research suggesting that people require a certain amount of sun exposure for optimal health. Past studies have linked low levels of vitamin D to increased rates of death, heart disease, diabetes, cancer, allergies, mental illness and other afflictions. However, it is still unclear whether low levels of vitamin D are the cause of these conditions or if they are a consequence.

In the latest investigation, Dutch researchers examined data from 380 white families with at least two siblings over age 90, with a brother aged at least 89 or a sister aged 91 or older, in the Leiden Longevity Study.

The study involved the siblings, their offspring and their offspring's partners for a total of 1,038 offspring and 461 controls.

Researchers controlled for factors that affect vitamin D levels like age, sex, body mass index, kidney function and supplement use. The team also looked at the genetic influence in three of genetic variations in 3 genes associated with vitamin D levels.

Researchers found that the offspring of nonagenarians, people over the age of 90, with at least one nonagenarian sibling, had lower levels of vitamin D as well as a lower frequency of common genetic variants in the CYP2R1 gene, a common genetic variant which predisposes people to higher levels of vitamin D.

"These findings support an association between low vitamin D levels and familial longevity," the study's authors concluded.

While the latest findings contradict those from previous studies, researchers say that a possible explanation for increased mortality seen in past research is that low vitamin D level may actually be the result from illness-associated weakness that limits sun exposure. Additionally, the association for low levels of vitamin D and cardiovascular disease in previous research may have been confounded with low physical activity and high body mass index.

While researchers from the latest study could not fully explain the link between low vitamin D levels and longevity, they hypothesize that the children of nonagenarians might have more of a protein that is believed to be an "aging suppressor".

"We speculate that offspring might have a higher expression of the klotho protein, which is hypothesized to be an 'aging suppressor' protein," van Heemst and her team wrote.

"Future research should focus on elucidating the mechanisms that explain the lower 25(OH) vitamin D levels in familial longevity and other genetic variants associated with vitamin D metabolism, such as the vitamin D receptor," they concluded.