Low Vitamin D Levels Linked to Early Signs of Kidney Disease

New York, NY (July 1, 2013) – 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.

"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."

Sunlight is the primary source of vitamin D for most people, but increased skin cancer awareness and more indoor time have contributed to vitamin D deficiency in the general population, researchers speculate. Secondary sources of vitamin D include supplements, certain sea foods, eggs and products fortified with vitamin D such as milk and orange juice.

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."

Urine Protein and Vitamin D Facts from the National Kidney Foundation

  • Albumin is a type of protein. When found in the urine it is known as albuminuria. The presence of albuminuria indicates the kidneys have some damage that prevents them from retaining protein in the body.
  • Two positive tests for albuminuria over several weeks are an early indication of kidney disease.
  • For patients with diabetes and/or established chronic kidney disease, albuminuria is associated with more rapid progression of their condition and a greater chance that kidney failure will develop.
  • Vitamin D is important for maintaining healthy bones. Muscle weakness may also occur if vitamin D levels are insufficient.

The National Kidney Foundation (NKF) is the leading organization in the U.S. dedicated to the awareness, prevention and treatment of kidney disease for hundreds of thousands of healthcare professionals, millions of patients and their families and tens of millions of Americans at risk. For more information, visit www.kidney.org.