In one of the largest studies of its kind, researchers found that consuming vitamin D supplements did not prevent adults from becoming depressed or improve their mood.
The Massachusetts team says its findings may finally put the popular myth to rest that a deficiency in the vitamin is associated with a higher risk of developing depression later in life. A study was published Tuesday in the journal JAMA.
“One scientific issue is that you actually need a very large number of study participants to tell whether or not a treatment is helping to prevent development of depression,” study lead author and principal investigator Dr. Olivia Okereke, a physician in the psychiatry department at Massachusetts General Hospital, said in a news release. “With nearly 20,000 people, our study was statistically powered to address this issue.”
Vitamin D is often called the “sunshine vitamin” because the skin can naturally make it when under the star. That is why during the winter, when the sun is not as intense and more time is spent indoors than out, people start to feel the impacts of seasonal affective disorder.
Studies have shown that exposure to sunlight increases mood, as well as levels of vitamin D in blood, but there is no direct evidence that proves the vitamin is responsible for that boost, Dr. Dale Archer, a clinical psychologist and fellow of the American Psychiatric Association, wrote in Psychology Today.
The researchers set out to understand if correlation equals causation. They gave half of the 18,353 men and women age 50 and older a vitamin D3 supplement and the other half a placebo over an average of five years, beginning in 2011, according to the study.
The participants either had no history of depression or did but had not received treatment for it in the past two years.
The team found there to be no “significant benefit” from the vitamin to prevent depression or improve mood over time based on questionnaires participants had to complete. However, “it’s not time to throw out your vitamin D yet, at least not without your doctor’s advice,” Okereke said.
The vitamin is known to promote bone and metabolic health by helping the body take up nutrients from foods. It differs from other vitamins in that every cell in the body has a receptor for it, functioning more like a hormone, according to Healthline. Signs of a deficiency include hair loss, bone and back pain, fatigue and frequent illness.
Vitamin D can be found in foods such as fish and egg yolks, but it’s often difficult to get what your body needs through diet alone.
It’s estimated that 1 billion people worldwide have a vitamin D deficiency or insufficiency, especially older adults, which has been linked to obesity, diabetes, cardiovascular disease, cancer and autoimmune disease, Archer wrote in Psychology Today.
People don’t spend as much time outside as generations past, and when they are, they apply sunscreen that blocks the rays responsible for producing the vitamin, according to Archer. This could explain why the deficiency is so common.
But one question remains: Does depression cause vitamin D levels to drop in the blood, or does the deficiency cause depression?
The researchers said they believe their study “may be the definitive answer to this question,” providing some clarity about vitamin supplements and mental health.