If you're trying to prevent or ward off a cold, those vitamin D supplements may not be much help.
Taking monthly vitamin D3 supplements didn't seem to have much of an effect on reducing the number or severity of colds (also known as upper respiratory tract infections), according to a new study in the Journal of the American Medical Association.
The randomized, controlled study included 322 healthy adults. Half of them received 200,000 IU of oral vitamin D at the beginning of the study (early 2010), followed by 200,000 IU of vitamin D a month later, and then 100,000 IU of vitamin D each month until the end of the study (late 2011). The other half of the participants were on the same regimen, but received only a placebo with no vitamin D.
At the start of the study, the average blood levels of vitamin D of the study participants was 29 nanograms per milliliter of blood. According to the National Institute of Health's Office of Dietary Supplements, having a vitamin D level between 20 and 49 nanograms is "generally considered adequate for bone and overall health in healthy individuals." Throughout the study, the participants who received the vitamin D had their blood vitamin D levels go up to more than 48 nanograms per milliliter of blood.
By the end of the study, there were 593 incidences of upper respiratory tract infections among the people who took the vitamin D. Meanwhile, there were 611 cases of the infections among people who took the placebo.
Overall, there was really no difference in the number and severity of colds between the two groups. People who took the vitamin D got 3.7 colds, on average, while people who took the placebo got 3.8 colds, on average. And colds for both groups lasted about 12 days, on average.
"We did not show a benefit of vitamin D supplementation in our study population; however, it is possible that vitamin D may prevent URTIs in other populations," the researchers who are from the University of Otago, Christchurch, in New Zealand, wrote in the study. They cited some past research suggesting an effect on vitamin D and colds among people who are deficient in the vitamin (people in this new study were largely not deficient in vitamin D).
In an accompanying editorial, Dr. Jeffrey A. Linder, M.D., MPH, an expert from Brigham and Women's Hospital and Harvard Medical School, wrote that the "results suggest that vitamin D should join the therapies listed in the Cochrane reviews as being ineffective for preventing or treating upper respiratory tract infections in healthy adults."
The new findings add to a growing body of literature exploring the effects of vitamin D on different aspects of health, said Dr. Alexandra Yamshchikov, an assistant professor of medicine at the Infectious Diseases Unit at the University of Rochester Medical Center who was not involved in the study.
"There's clear benefits to vitamin D supplements for bone health, and for that reason vitamin D status should be maximized for patients who are deficient or insufficient," Yamshchikov, who has previously studied vitamin D's role in tuberculosis recovery, told HuffPost. "But for these other nontraditional effects of vitamin D, the jury is still out."
Even though the study was relatively small, especially compared with other studies that involved thousands and hundreds of thousands of people, Yamshchikov said it was very well-designed. However, she noted that the results are not the "last say" on the subject considering some limitations to the study that the researchers also acknowledged.
For example, people in the study received the supplements once a month in order to ensure that they would take them (since it's harder to maintain 100 percent compliance with a daily pill, versus a once-a-month pill). However, it's still unknown whether taking a daily supplement could have different effects than a monthly supplement.
Also, past research has suggested that vitamin D supplementation among children who are deficient in the vitamin could help to provide some cold protection, as The Atlantic reported earlier this year. However, everyone in this new study was sufficient in their vitamin D levels -- so more research may be needed to see if vitamin D supplementation among people who are deficient in it could help protect them from colds, she noted.
"The literature on the immune effects [of vitamin D] is mixed -- there's evidence to promote vitamin D for bone health, but the literature on immune effects is mixed," Yamshchikov said. "We understand how it may affect immune response ... such as with association-type of studies, but there have been few prospectively designed randomized controlled studies."
Ultimately, she advised people who have questions about vitamin D supplementation to talk to their doctors to see if it's needed in their case.
Got a cold yourself that you just can't seem to beat? HuffPost's Sarah Klein reported on some things to eat and drink that could help, as recommended by registered dietitian Ilyse Schapiro, R.D., C.D.N.:
Yes, Mom, I'm drinking plenty of fluids. While there hasn't been any rigorous scientific research into the legitimacy of this cold cure, staying hydrated is important. A little extra H20 can also help thin mucus, possibly easing some of that congestion, says Schapiro, and "help to flush everything out." Lovely. Plain water may be the best, but tea is another good option, she says. Warm liquid can soothe a sore throat and further ease congestion, and tea is also rich in infection-fighting antioxidants, she adds. Flickr photo by brad montgomery
One of my co-workers suggested not just any liquid, but juice in particular. I know orange juice has a healthy reputation for all that immunity-boosting vitamin C, but juice also gets a bad rap for containing a heck of a lot of calories and not a lot of bulk. Schapiro agrees. "You don't want beverages with added sugars," she says. "Extra sugar hinders white blood cells from fighting infection." If you're looking for that dose of C, go straight to the unprocessed source. Have an orange or a grapefruit, or squeeze some lemon into your tea -- the fruit has more fiber, so it'll be more filling, and you'll only get the natural sugars, not the added ones in juice, says Schapiro. You can even find vitamin C in some surprising places, like kale and red bell peppers, she adds, if you're not in the mood for citrus. However, before you run out for a week's worth of grapefruit, keep in mind that the jury is still out on vitamin C's real cold-busting benefit. A 2007 study that followed more than 11,000 people over several decades found that the average person isn't benefitted all that much by a daily dose of vitamin C. Turns out, it's much more helpful to bodies under extreme physical stress, like marathon runners. Flickr photo by tasselflower
By day three of my cold, I'd had soup for more meals than not. It's easy to sip on when you're not so hungry (a cold-induced phenomenon I am not usually plagued by), and it's comforting, but does it really help? While the warmth could break up some congestion, there does seem to be something about soup -- and chicken soup in particular -- that works to fight against infections. "It's anti-inflammatory," says Schapiro, a finding supported by a 2000 study that examined the components of chicken soup individually, as well as the contents of the bowl as a whole. The researchers found you might feel even better if you can convince someone to make it for you. If only. Flickr photo by Robert Couse-Baker
I had to essentially force-feed myself the soup, but Schapiro says it's important to still get some protein "even when you don't feel like eating anything." Fish, chicken and turkey can help the organs that make your cold-destroying white blood cells, she says. Just stay away from fatty things, like a juicy steak or anything fried, since these foods are harder to digest and may suppress your immune system, she says. Flickr photo by bensonk42
Another co-worker offered the following cure: Steep some fresh ginger in boiling water until the water turns yellow, then drink it like tea with some honey. At the time, I couldn't bring myself to walk down and then back up the four flights of stairs to my apartment just for some knobby ginger, but turns out she was onto something. The root has anti-inflammatory properties, says Schapiro, and you can get a "two-for-one" by cooking up a ginger-flavored chicken dish, she suggests. Flickr photo by stevendepolo
"Eat garlic!" my boyfriend texted me, when I whined about my symptoms. "It's supposed to kill bacteria if you catch it early enough." My first reaction, as a health editor, was to wonder how he came by such wisdom, but turns out he's right (swoon). Regular garlic eaters seem to fight off colds, possibly because of the compound allicin's ability to block infections, the New York Times reported. "I would cook with it," says Schapiro. "Put it in the chicken soup, or with a chicken dish, or if you can tolerate it, cook vegetables like broccoli with it, for some extra antioxidants and vitamins."
I don't think anyone is going to throw a house party mid-cold, but maybe you're tempted to try a glass of wine to help you sleep. However, I have a hunch alcohol is what got me in trouble in the first place: a weekend of a little too intense exercise (a long run Saturday and a 90-minute soccer game on Sunday) washed down with a couple of beers instead of a couple of glasses (gallons?) of water. "There are properties of alcohol that decrease your immune system," says Schapiro, "it suppresses it, it doesn't let your body fight infection and it also dehydrates you." Guilty. Flickr photo by paulaloe
It's tempting to drown those sniffly sorrows in the bottom of an ice cream sundae, but rumor has it that dairy might make things worse. For every study that says you should avoid dairy products when you have a cold, there's one that says you needn't bother, says Schapiro. "Some people say to avoid it because it increases mucus, but others say it doesn't necessarily," she says. "I say try it, and if it doesn't aggravate you, then go for it," since dairy products can be good sources of protein and vitamin D, which can both help fight infections, she says. Flickr photo by SeRVe Photography