By Amy Norton
FRIDAY, Sept. 20, 2019 (HealthDay News) -- Young and middle-aged adults with low vitamin D levels may live shorter lives, a large study suggests.
The findings come from a 20-year follow-up of more than 78,000 Austrian adults. Researchers found that those with low vitamin D levels in their blood were nearly three times more likely to die during the study period than those with adequate levels.
When it came to the cause of death, vitamin D levels were most clearly linked to deaths from diabetes complications.
The findings were to be presented Friday at the annual meeting of the European Association for the Study of Diabetes, in Barcelona -- and are considered preliminary. Experts said they do not prove that low vitamin D levels, per se, cut people's lives short.
But the results add to a large body of evidence tying inadequate vitamin D to various health effects -- beyond the long-recognized consequence of thinner, weaker bones. Studies have also pointed to higher risks of conditions like diabetes and high blood pressure, certain cancers, and autoimmune diseases such as multiple sclerosis.
"The role of vitamin D in the body appears to be more than simply assisting calcium absorption and bone health," said Connie Diekman, a registered dietitian who was not involved in the study.
However, the research is "still evolving," noted Diekman, who has served as president of the nonprofit Academy of Nutrition and Dietetics. That means it's still unclear whether boosting your vitamin D intake -- through food or pills -- will prevent various diseases or lengthen your life.
In fact, a recent study, published in the New England Journal of Medicine, yielded disappointing results: Researchers found that vitamin D supplements did not help prevent type 2 diabetes in people at high risk of the disease.
But that may be in part because supplements later in life might not be enough to prevent a disease, according to Dr. Rodrig Marculescu, the lead researcher on the current study.
Many health conditions, including type 2 diabetes, get their start earlier in life, said Marculescu, of the Medical University of Vienna in Austria.
On the other hand, he said, vitamin D supplements might have more of an impact on the odds of dying from a disease.
His team found a clear relationship between blood vitamin D levels and the risk of early death -- especially among people who were younger than 60: Those with levels of 10 nmol/L (nanomoles per liter) or less had almost a three-times higher risk of dying during the study, versus those with adequate levels (50 nmol/L).
In contrast, middle-aged and younger people with vitamin D levels at or above 90 nmol/L had a lower death risk than those at the 50 mark.
In general, vitamin D concentrations of 50 nmol/L or higher are considered to be high enough for overall health, according to the U.S. National Institutes of Health.
When the researchers zeroed in on causes of death, it turned out that vitamin D levels showed only weak connections to heart disease and cancer. Instead, people with low levels (below 50) had a more than fourfold higher risk of dying from diabetes complications, versus those with adequate levels.
It's not clear why. But, Marculescu said, there are plausible reasons that vitamin D levels would be particularly linked to diabetes: The vitamin, which acts as a hormone in the body, helps regulate the immune system. That's relevant to type 1 diabetes, Marculescu noted, because it is an autoimmune disease.
Vitamin D is also important to the cells that produce the hormone insulin -- which regulates blood sugar -- and to the body's sensitivity to insulin. That's relevant to type 2 diabetes, Marculescu pointed out.
For now, he said, the findings "further strengthen the already very strong rationale for intensifying vitamin D supplementation, especially during childhood and at younger ages."
Specifically, he pointed to recommendations from the Endocrine Society. They suggest that adults get 1,500 to 2,000 IU of vitamin D per day, while children and teenagers get 600 to 1,000 IU.
The body naturally synthesizes vitamin D when sunlight hits the skin, but cold climates -- and concerns about sun exposure -- can limit that source.
Diekman suggested that people have their blood vitamin D level checked. If it's low, she said, talk to your doctor about how to boost it -- whether through supplements or foods such as vitamin D-fortified dairy products, juice or cereal.