(NaturalNews) Vitamin D deficiency may double the risk of schizophrenia, according to a study conducted by researchers from Isfahan University of Medical Sciences in Iran and published in the Journal of Clinical Endocrinology & Metabolism.
According to some estimates, that may mean that 75 percent of the US population is at double the usual risk of schizophrenia!
"When we examined the findings of several observational studies on vitamin D and schizophrenia, we found people with schizophrenia have lower vitamin D levels than healthy people," said researcher Ahmad Esmaillzadeh, PhD. "Vitamin D deficiency is quite common among people with schizophrenia."
Schizophrenia is a potentially severe mental illness that can be characterized by delusions and hallucinations. Research has shown that the disease is more common in cold climates and at latitudes far from the equator.
This is a pattern, seen in many diseases, that makes researchers look for a potential connection with vitamin D deficiency.
"This is the first comprehensive meta-analysis to study the relationship between the two conditions," Esmaillzadeh said.
Vitamin D is produced by the skin upon exposure to ultraviolet radiation from sunlight. Farther from the equator, the sun is less strong, and people are at higher risk for vitamin D deficiency. Researchers estimate that 1 billion people worldwide may have insufficient vitamin D levels due to not getting enough exposure to sunlight (unprotected by clothing or sunscreen).
The researchers reviewed the results of 19 prior observational studies conducted on a total of 2,804 people. The researchers found that people with vitamin D deficiency were 2.16 times more likely to be schizophrenic than people with sufficient vitamin D levels. Of schizophrenic participants, 65 percent were vitamin D deficient. On average, schizophrenic participants had vitamin D blood levels 5.91 ng/ml lower than non-schizophrenic participants.
While scientists have long known that vitamin D is critical for bone health and for preventing rickets and osteoporosis, it is only recently that they have begun to discover the role that it plays in preventing other diseases and conditions.
"There is a growing trend in the nutrition science field to consider vitamin D and its relationship to conditions such as diabetes, cancer, heart disease and depression," Esmaillzadeh said. "Our findings support the theory that vitamin D may have a significant impact on psychiatric health. More research is needed to determine how the growing problem of vitamin D deficiency may be affecting our overall health."
How many people are at risk?
Because vitamin D deficiency is so widespread, the new study suggests that vast segments of the U.S. population may be making themselves more vulnerable to schizophrenia by not getting enough sunlight.
One study, published in the Archives of Internal Medicine in 2009, estimated that three-quarters of teenagers and adults in the United States are vitamin D deficient. A full 97 percent of African American adults were found to have insufficient levels.
The researchers used 30 ng/ml as the cutoff for sufficient levels.
"We're just starting to scratch the surface of what the health effects of vitamin D are," said researcher Adit Ginde of the University of Colorado at Denver. "There's reason to pay attention for sure."
Because the functions of vitamin D are still poorly understood, researchers remain divided over exactly what blood levels of the vitamin are ideal. However, even people who use a lower standard agree that deficiency is widespread.
For example, Purdue University professor Jim Fleet, who was critical of Ginde's study, said that even using a stricter threshold, 40 percent of African Americans are considered vitamin D deficient.
"If you look at people in the categories that we worry about," he said, "that's still a lot of people."