Vitamin D levels may be able to predict early kidney disease, according to a new study published in the July issue of the National Kidney Foundation's American Journal of Kidney Diseases.

Researchers found that those who were deficient in vitamin D were more than twice as likely to develop albuminuria (a type of protein in the urine) over a period of five years. Albuminuria is an early indication of kidney damage as healthy kidneys capture protein for use in the body.

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"There have been a number of studies establishing a relationship between vitamin D levels and kidney disease," said Thomas Manley, Director of Scientific Activities for the National Kidney Foundation. "This study supports that relationship and shows that a low vitamin D level increases the likelihood of developing protein in the urine, even among a general population."

It is unknown if vitamin D levels are a cause or condition of kidney damage. However, the research could bolster the case for more careful vitamin D monitoring and using vitamin D levels to identify individuals who may be at risk for developing kidney disease.

Key findings

Of more than 5,800 men and women without protein in their urine, 3.8% developed albuminuria during a five-year follow-up period. Those patients deficient in a form of vitamin D known as serum 25-hydroxyvitamin D, were found to be 84% more likely to have albuminuria. Deficiency was defined as having less than 15 nanograms of vitamin D per milliliter of blood.

Adjusted for age and other lifestyle factors, individuals with vitamin D deficiency were found to have a 70% increase in albuminuria.

"There is mounting evidence of the benefits of correcting vitamin D levels to prevent or delay the development of albuminuria in the general population," said the study's lead researcher, Matthew Damasiewicz, MD, of Monash Medical Centre in Melbourne, Australia. "It is also likely that patients with chronic conditions such as CKD may need higher vitamin D levels than the general healthy population."