Importantly, the symptoms of the flu and the common cold, both of which are caused by viruses, can be very similar, so it’s tough to tell which one you have.
That said, neither orange juice nor vitamin C supplements will likely do much good against either virus. Studies have found that vitamin C does nothing to prevent or treat the common cold — and the research on vitamin C and the flu has been inconclusive.
Instead of vitamin C, the available evidence does support the use of another supplement — zinc.
‘Routine vitamin C supplementation is not justified’
A 2013 review of 29 trials which involved more than 11,300 people found “no consistent effect of vitamin C … on the duration or severity of colds.” The only place the authors observed some benefits of vitamin C supplementation was in marathon runners, skiers, and soldiers on “subarctic exercise” — and even in those small populations, the observed effect was small.
“The failure of vitamin C supplementation to reduce the incidence of colds in the general population indicates that routine vitamin C supplementation is not justified,” the study authors wrote.
And megadoses of vitamin C — on the order of 2,000 milligrams or more — may come with substantial harms, including raising your risk of painful kidney stones.
If you want to increase your overall vitamin and mineral intake, research backs getting it from fresh fruits and vegetables. This is the best way for your body to process it and ensures you get the most nutrients possible.
Zinc may be your best bet against the common cold
Unlike vitamin C, which studies have found likely does nothing to prevent or treat the common cold, zinc may actually be worth a shot this season. The mineral seems to interfere with the replication of rhinoviruses, the bugs that cause the common cold.
In a 2011 review of studies of people who’d recently gotten sick, researchers looked at those who’d started taking zinc and compared them with those who just took a placebo. The ones on zinc had shorter colds and less severe symptoms.
Zinc is a trace element that the cells of our immune system rely on to function. Not getting enough zinc (Harvard Medical School researchers recommend 15-25 mg of zinc per day) can affect the functioning of our T-cells and other immune cells. But it’s also important not to get too much: an excess of the supplement may actually interfere with the immune system’s functioning and have the opposite of the intended result.
So instead of chugging fizzy drinks loaded with vitamin C, stick to getting the nutrient from food. Strawberries and many other fruits and veggies are a great source. And if you aren’t getting enough zinc in your diet, try a zinc supplement. Chickpeas, kidney beans, mushrooms, crab, and chicken are all rich in zinc, and zinc-rich lozenges may also help boost your intake.