No doubt about it: Vitamin D is a rock-star nutrient. Not getting enough of it has been linked to health problems such as cancer, weak bones, multiple sclerosis, arthritis, heart disease and Type 1 diabetes, as well as fatigue and aches and pains. Low levels have also been associated with an increased risk for depression. Now a growing body of research is exploring whether or not getting enough D can keep you from feeling blue.
So far, the jury is still out, says Dr. Sherwood Brown, vice chair for faculty research development in psychiatry at the University of Texas Southwestern Medical Center in Dallas.
Brown led a large study, published in the Mayo Clinic Proceedings in 2011, that assessed depression and vitamin D levels in 12,594 people who visited the Cooper Clinic in Dallas between 2006 and 2010. He found that those who had higher levels of vitamin D had a significantly decreased risk for depression, especially if they had a prior history of feeling down. Low D levels, on the other hand, were associated with symptoms of depression. The study didn’t assess whether increasing D levels eased depression.
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Vitamin D receptors are found throughout the body, including in the brain, and D could directly affect these receptors, Brown explains. Another theory is that low levels of D may be associated with inflammation, which may play a role in depression. However, more research is needed to tease out the cause and effect, if any.
At a 2012 meeting of The Endocrine Society, researchers reported on three women ages 42 to 66 who had been diagnosed with moderate to severe clinical depression and were taking antidepressants. (The women were also being treated for Type 2 diabetes or an under-active thyroid.) All three women had a vitamin D deficiency, meaning their D levels were less than 20 nanograms per milliliter of blood (ng/mL). Normal D levels are considered to be 20 ng/mL or above.
After the women were treated with vitamin D supplements over the course of eight to 12 weeks, their D levels returned to a normal range and their symptoms of depression eased.
According to the researchers, “detection and treatment of vitamin D deficiency in patients with depression may be an easy and cost-effective adjunct to mainstream therapies; however, more research is needed to definitively confirm these findings.”
Other researchers analyzed the amount of D nearly 82,000 women obtained from food and found that those who got 800 IUs or more every day were 21 percent less likely to be depressed than were women who got less than 100 IUs per day. In women who were not depressed when the study began, those who got 400 IUs per day or more of vitamin D had a 20 percent lower risk of developing depression three years down the road. Findings on the risk of depression in women who got their vitamin D from supplements were not consistent. The analysis, which involved women ages 50 to 79 participating in the landmark Women’s Health Initiative, was published in 2011 in the American Journal of Clinical Nutrition.
In 2012, the same researchers reported that taking a daily supplement containing 400 IUs of D, as well as 10000 mg of calcium, for two years didn’t influence the risk of depression; though the researchers conceded that the dosage of D studied may have been too low to affect risk.
The prospect of easing even mild symptoms of depression or preventing the condition with vitamin D is tantalizing. An estimated one in 10 Americans suffers from depression, according to the Centers for Disease Control and Prevention. Among those most likely to be depressed are 45- to 64-year-olds and women. Eleven percent of Americans ages 12 and over take antidepressants, reports the CDC, and more than 60 percent have done so for two years or more; 14 percent have used the drugs for 10 years or more. If D turns out to have depression-preventing or easing powers, the implications would be huge.
The Institute of Medicine recommends aiming for at least 600 IUs of D per day until age 70. After that people may need as much as 800 IUs per day, according to the IOM.
Sunshine is our main source of vitamin D; the sun’s rays trigger its production in skin. But because of concerns about skin cancer, many people avoid the sun or wear sun protective clothing or sunscreen. What’s more, the angle of the sun from late fall through early spring means Americans in northern states simply can’t get enough sun for much of the year.
While one study did find that the D in food eased depression, it’s pretty tough to obtain enough of the sunshine vitamin from a typical meal. The best source is fatty fish: 3 oz. of swordfish has 566 IUs; 3 oz. of salmon, 447 IUs; and 3 oz. of canned tuna fish, 154 IUs. One tablespoon of cod liver oil has a whopping 1,360 IUs. Next best: One cup of D-fortified milk has about 120 IUs of D. One large egg has 41 IUs and a cup of D-fortified cereal has 40 IUs.
Because lots of people don’t eat enough fatty fish or drink enough milk to meet their daily D quota, some experts recommend taking a D supplement on top of whatever D they get from food and sun exposure. The safe upper limit for D in people over age nine is 4000 IUs per day, so it’s hard to overdo it.
Even if you do manage to down enough D, the $64,000 question remains: Do people with low D levels develop depression or do depressed people tend to have lower levels of D because they eat fewer foods containing D and are more likely to stay indoors, avoiding the sun?
Stay tuned. Early promising studies on D and depression must be confirmed, first of all. Then, says Brown, “We need to figure out exactly which patients would respond best to Vitamin D.” What’s more, experts must determine whether D alone is enough to prevent or ease depression or if people would need D plus antidepressants. “There are a lot of unanswered questions,” he says. The good news: “We’ll have an answer in the next few years,” notes Brown. “It’s an active area of research.”
In the meantime, it’s smart to meet the IOM guidelines for D. Also, ask your doctor if it makes sense to have your D levels checked. If it turns out they’re low, she may prescribe a D supplement to boost them into the normal range.