3 Top Supplements for Colds and Flu , shares the supplements that may help prevent you from getting sick. Thanksgiving Dinner, Hold the Guilt After you binge on Thursday, three ways to purge your conscience. Food-Label Guide: Decode the Buzzwords "Whole grain" and "reduced fat" foods may not be what you think. Find out what food-label buzzwords really mean!Zinc, vitamin C, vitamin D, old-fashioned chicken soup. Chances are you’ve probably tried all of these remedies to ward off symptoms of a cold, but scientists now say that you can cross at least one of them off your list. In the most rigorous study to date investigating whether vitamin D can protect against colds, researchers found that healthy adults who took large doses of the supplement were no less likely to come down with upper respiratory infections — including colds, flu and sinus infections — than those taking placebo. The new study, led by Dr. David Murdoch and his colleagues at the University of Otago in New Zealand, followed 322 healthy participants who were randomly assigned to take either vitamin D or a placebo on a monthly basis for 18 months.
All participants came to the research facility so that scientists could observe them taking the pills, but neither the volunteers nor the scientists knew which pills contained the vitamin and which were placebo. Those getting vitamin D supplements received 200,000 IU for each of the first two months, and then 100,000 IU monthly for the remainder of the trial. That amounts to more than 3,000 IU a day, when health officials currently recommend that most adults get about 600 IU of vitamin D daily (primarily to maintain bone health and avoid the bone-weakening disease of osteoporosis). By the end of the study, participants in the vitamin D group had developed a cold or flu an average 3.7 times, compared with 3.8 times in the placebo group. Taking vitamin D also had no impact on the severity or duration of people’s symptoms nor did it reduce the number of workdays they missed. (MORE: Megadoses of Vitamin D Offer No Benefit) Scientists started looking at vitamin D for cold prevention after early studies showed that tuberculosis patients who had genes that efficiently metabolized vitamin D were less prone to serious lung infections.
There was also the intriguing observation that people who lived in sunnier climates — and therefore presumably had higher levels of vitamin D, since the skin makes the vitamin when exposed to sunlight — also tended to have fewer colds than those who lived in areas with less exposure to the sun. Previous clinical trials have led to similarly disappointing results, however. But the authors of the current study note that people who are deficient in vitamin D, which is thought to contribute to immune function, may yet benefit from taking supplements. Studies involving children in Mongolia, for example, where the harsh climate prevents much sun exposure, showed that vitamin D supplements helped lower respiratory infections by 50%. As for the protective effect of extra vitamin D in healthy adults who already have normal levels: “Whether vitamin D can prevent colds is pretty much done and dusted in healthy people,” says Murdoch. “Now we need to focus on other groups.” (MORE: Vitamins and Supplements Linked to Higher Risk of Death)
Recent studies also show the supplement may not be as helpful as hoped in preventing other diseases. For example, rigorous trials suggest that taking vitamin D in low-dose supplements (400 IU) doesn’t help healthy postmenopausal women avoid bone fractures — but higher doses may still be helpful, and the supplements do help prevent bone breaks in women living in nursing homes or assisted-living facilities. Also, taking vitamin D does not lower the risk of developing breast cancer. That’s not to say that maintaining vitamin D levels isn’t necessary for good health overall: the vitamin is needed for the body to soak up bone-building calcium from foods. Good dietary sources of D include dairy products such as yogurt, eggs, cheese and fortified milk. Getting at least a few minutes of sunlight a day is also enough for the body to make adequate vitamin D, though experts note that increased public health warnings about the risk of skin cancer from sun exposure may be leading to more cases of D deficiency than doctors think.
Whether or not such people may benefit from taking supplements during cold and flu season, Murdoch’s latest findings suggest that for the majority of healthy individuals, chicken soup may have to do for now. The new study was published in the Journal of the American Medical Association. MORE: Is Vitaminwater Really a Health Drink? Alice Park is a writer at TIME. Find her on Twitter at @aliceparkny. You can also continue the discussion on TIME’s Facebook page and on Twitter at @TIME.It wouldn’t be surprising if pharmacies are seeing a surge in demand for vitamin D tablets. After all, a new study just came out suggesting the sunshine vitamin can reduce the risk of catching a cold or the flu.“Vitamin D ‘proved to cut risk of colds and flu,’” declared a headline in the Guardian. Medscape said, “Vitamin D may protect against respiratory infections,” while the BBC ran a headline that said: “Vitamin D pills ‘could stop colds or flu.’” Who wouldn’t be willing to pop a few vitamins in order to ward off the congestion, fatigue and fever that can accompany seasonal colds and influenza?
But you may want to hold off before you run out to stock your medicine cabinet.The scientific community has been increasingly interested in the power of vitamin D over the last decade, as some research has found it may help reduce the risk of everything from multiple sclerosis to bone fractures. The problem is that most of the research is conflicting and inconsistent. Despite the promising headlines, the new study linking vitamin D to a reduced risk of respiratory infections is no exception. The paper, published in the British Medical Journal on Wednesday, was a meta-analysis. That means researchers look at a number of different studies on vitamin D and respiratory infections – 25, in this case – and synthesize the results to determine what conclusions can be drawn from the large pool of evidence.In the new study, researchers concluded that supplements of vitamin D were linked to a 12-per-cent reduction in the risk of catching one acute respiratory infection. They conclude that 33 people would need to take supplements to prevent one respiratory infection.
Among those who are severely vitamin-D-deficient, only four people would need supplements to prevent a cold.However, there are some major caveats to keep in mind.If it sounds too good to be true …An editorial published alongside the new study puts the results in perspective. Yes, the researchers found a risk reduction of 12 per cent. But it was a relative risk reduction, which actually doesn’t tell us much. A relative risk reduction in this instance refers to the difference in the number of people who took vitamin D supplements and got a respiratory infection compared to those who didn’t take supplements and caught one.It’s much more useful to look at the absolute risk, or the actual numbers, to see how well the supplements performed. It turns out that 42.2 per cent of the non-vitamin-D study participants caught at least one acute respiratory tract infection compared to 40.3 per cent of the people who took supplements – a difference of 1.9 per cent.“It seems unlikely that the general population would consider a 2-per-cent absolute risk reduction sufficient justification to take supplements,” wrote the editorial authors, who have previously published research questioning the benefits of vitamin D for bone health.
The editorial also points out that there was no single definition of what constitutes a respiratory-tract infection in the meta-analysis. Some studies used lab-confirmed cases of the flu, others included self-reported or parent-reported colds – factors that make it difficult to interpret the study results or apply them to the general population, the authors wrote.The study authors wrote their own response to the editorial, pointing out their overall skepticism of the benefits of vitamin D in previously published studies. The authors defended their findings and pointed out that only 33 people need supplements in order to prevent one respiratory-tract infection.Dr. James McCormack, a professor in the faculty of pharmaceutical sciences at the University of British Columbia who focuses on the appropriate use of medication, said this study underscores some of the classic problems with attempting to draw sweeping conclusions from a study, particularly when there are impassioned “believers” on both sides of a debate.“