April 20 (UPI) -- People deficient in vitamin D might have a greater risk of developing diabetes, report researchers in a new study.
Researchers at the University of California San Diego School of Medicine and Seoul National University studied 903 healthy adults without pre-diabetes or diabetes during clinic visits from 1997 to 1999, and followed up with them for 10 years, to study their levels of 25-hydroxyvitamin and their medical condition. Their findings were published this week in PLOS One.
"Further research is needed on whether high 25-hydroxyvitamin D levels might prevent type 2 diabetes or the transition from pre-diabetes to diabetes," study co-author Dr. Cedric F. Garland, adjunct professor in the UC San Diego School of Medicine Department of Family Medicine and Public Health, said in a press release. "But this paper and past research indicate there is a strong association."
The 25-hydroxyvitamin D, which is known as the "sunshine" vitamin because it's produced in your skin in response to sunlight, also can be received through certain foods and supplements. The vitamin helps in growth and development of bones and teeth, and resistance against certain diseases.
Among the study participants, who had a mean age of 74, researchers found 47 new cases of diabetes and 337 new cases of pre-diabetes.
The minimum healthy level of 25-hydroxyvitamin D in blood plasma was listed as 30 nanograms per milliliter, which is 10 ng/ml above the level recommended in 2010 by the Institute of Medicine, now part of The National Academies.
"We found that participants with blood levels of 25-hydroxyvitamin D that were above 30 ng/ml had one-third of the risk of diabetes and those with levels above 50 ng/ml had one-fifth of the risk of developing diabetes," first author Dr. Sue K. Park, of the Department of Preventive Medicine at Seoul National University College of Medicine in South Korea, said.
Those below 30 ng/ml were considered vitamin D deficient and up to five times at greater risk for developing diabetes than those above 50 ng/ml.
Garland and his late brother Frank C. Garland, also an epidemiologist, published a paper in 1980 that vitamin D and calcium combined to reduce the risk of colon cancer. Then Garlan and colleagues found associations with breast, lung and bladder cancers.
To reach the D levels of 30 ng/ml, Garland said it would require dietary supplements of 3,000 to 5,000 international units per day, but less with moderate daily sun exposure.
The recommended average daily amount of vitamin D is 400 IU for children up to 1 year, 600 IU for ages 1 to 70 years and 800 IU for persons over 70, according to the National Institutes of Health.
Good food sources for vitamin D include salmon, sardines, egg yolk, shrimp, and fortified milk, cereal, yogurt and orange juice.