Do Vitamins Prevent Cold and Flu?
When it comes to upper respiratory infections, can vitamins make a difference? It may depend on what you’re taking.
Two vitamins have come to the forefront as possible cold- and flu-stoppers. Both vitamin C and vitamin D have been studied as potentially preventative treatments to these diseases. Both seem to have some effectiveness in certain ways. Whether they improve the immune system’s ability to fight disease is still being studied, but here’s what we’ve learned so far.
On its surface, vitamin C has a lot going for it. It is a necessary nutrient found in lots of the foods we eat on a regular basis. Those foods include oranges, red bell peppers, kale, and broccoli for starters. It’s found in orange juice, which is also a relatively gentle food for digestive discomfort.
The research for this nutrient as a remedy for respiratory infections splits along two lines. One line of research attempts to understand whether high doses taken on a regular basis can prevent colds. The second line of research tries to answer whether high doses taken during a respiratory infection may decrease the duration of the disease.
On the first question—whether daily, high doses can prevent colds—has come up negative. There seems to be no solid, scientific evidence that this nutrient can keep a cold from developing. One possible exception is in the case of those who experience brief episodes of severe physical exercise or frigid environments—they may benefit from regular, high doses.
On the second question—whether high doses can reduce the duration of an illness—is inconclusive, but what evidence is available suggests it may have some benefit.
Different people seem to respond differently. For some, 1,000 mg seems to be helpful. For others, it takes 2,000 mg. Be careful: at these high doses, some people will experience diarrhea and nausea.
Vitamin D supplements have been tested to discover if they can prevent colds and the flu. Three large trials have come to contradictory conclusions.
In the first trial, scientists from the University of Otago in New Zealand followed 322 otherwise healthy adults for a year and a half. The study found that people who took supplements got sick about as often as people who didn’t. A second trial of more than 2,000 adults ages 45-75 also found no significant results from taking supplements.
However, a third trial performed by scientists from McMaster University found more promising results for those taking supplements. In this study, 600 students were tested. Some were given vitamin D, while others weren’t. The students given the extra nutrients were significantly less likely to contract an upper respiratory tract infection.
You’ll need to work a little harder to find natural food sources for your “daily D,” though some foods are fortified with this nutrient, making it easier to get it into your diet. Fortified foods include milk and some orange juices. Natural sources include fatty fish like mackerel and tuna, and swordfish and salmon have particularly high levels. Unfortunately, these fish may also contain high levels of mercury.