"About 70 percent of the population of the United States has insufficient levels of vitamin D," says Adrian Gombart, a principal investigator with the Linus Pauling Institute at Oregon State University. "This is a critical issue as we learn more about the many roles it may play in fighting infection, balancing your immune response, helping to address autoimmune problems, and even preventing heart disease."
People with diabetes may have even lower levels of vitamin D, according to a review last year in The Diabetes Educator. People at risk of diabetes and the metabolic syndrome (or syndrome x) also have low vitamin D levels.
Recent research found that 19 percent of people with type 2 diabetes probably suffer from major depression and an additional two-thirds of us have at least some depressive symptoms. People with diabetes are twice as likely to be depressed as other people.
Likewise, people with very low levels of vitamin D circulating in their blood are much more likely to be depressed that those with normal levels. This is the result of new research presented at this month's American Heart Association Scientific Conference 2009 in Orlando, Florida.
Heidi T. May, M.D., and six of her associates from Utah's Intermountain Medical Center started by testing a hypothesis. They wanted to see if the dramatic increase in depression during the past century and the reduced exposure to vitamin D from the sun were connected. We get less sun now as we spend more time indoors and cover ourselves ever more effectively with sunscreen whenever we go out.
The researchers studied 8,680 people who had both a cardiovascular event -- heart trouble -- and a measured level of vitamin D. Only those with a diagnosis of depression upon hospitalization satisfied their definition of depression.
Then, they divided the people into three groups based on their vitamin D levels. A normal level, they decided, was more than 30 ng/ml (other researchers like Dr. Neil Binkley set the normal level higher, at 40 ng/ml or even more). A low level was 15-30 ng/ml. A very low level was less than 15 ng/ml.
After following their subjects for more than a year, the researchers found that those who had very low levels were one-third more likely to develop depression than those with normal levels. The association was even stronger among those with no prior diagnose of depression.
Tellingly, the association was also especially strong in December, January, and February. Even Utah, where the people they studied live, doesn't have as much direct sun in winter.
Everyone needs to know his or her levels of vitamin D. Those of us who have diabetes have an extra reason, and anyone who also gets depressed doesn't need to think twice.
The first step is to have a lab test your levels of vitamin D. You can order a standardized test through your doctor or get one directly from GrassrootsHealth. This is a blood spot test kit to be used at home, unless you are unlucky enough to live in New York. GrassrootsHealth tests my levels every six months.
The second step is to decide how much vitamin D to take. "New evidence indicates that the intake should be 2,000 IU per day," GrassrootsHealth says. "Intake of 2,000 IU/day is the current upper limit of the National Academy of Sciences, Institute of Medicine, Food and Nutrition Board. New evidence also indicates that the upper limit should be raised substantially. The levels that are needed to prevent a substantial proportion of cancer would also be effective in substantially reducing risk of fractures, type 1 childhood diabetes, and multiple sclerosis. Greater oral intakes of vitamin D3 may be needed in the aged and in individuals who spend little time outdoors..."
Others recommend a much higher level, 5,000 IU per day or more, as I wrote in my most recent essay here. As I also wrote in that essay, vitamin D seems to treat a huge range of conditions. Now add depression to that long list.