As we head into winter, cold and flu season draws ever nearer.

Those of us trying to prime our immune system for the onslaught of diseases might be reaching for supplements alongside staying active and trying to eat well.

But the NHS says some of those efforts may be in vain.

Though the service advises British adults to consider taking vitamin D in the darker months, their entry on the common cold reads: “There’s little evidence that supplements such as vitamin C, echinacea or garlic prevent colds or help you get better more quickly.”

It can be a tough pill to swallow, even if it means one less actual capsule to gulp down.

But it’s not so much that supplements like these are proven to be bad or even completely ineffective: it’s just that the NHS isn’t convinced by the conflicting evidence that they do work.

Microbiologist Morticia shared a video explaining that “there is actually no such thing as an ‘immune booster’” outside of vaccines, adding that ingredients like vitamin C and ginger root are “not boosting your immune system.”

That’s not to say eating a balanced and varied diet isn’t good for your immune system or even that vitamin C isn’t part of a good immune response, but that vitamin supplements may not act as straightforwardly on our bodies as we think.

Morticia mentions how iron supplements for iron deficiency can take months to work, despite seeming like a straightforward answer to the issue: she also points out that hydrogen peroxide is crucial to white blood cells’ disease-fighting power, but nobody is suggesting drinking that to see us through a sniffle.

A 2013 review of studies by Cochrane found that “trials of high doses of vitamin C administered therapeutically, starting after the onset of symptoms, showed no consistent effect on the duration or severity of common cold symptoms.”

Akiko Iwasaki, an immunologist at Yale University, told BBC Future that “There are three different components to immunity.”

“There’s things like skin, the airways and the mucus membranes that are there to begin with, and they provide a barrier to infection. But once the virus gets past these defences, then you have to induce the ‘innate’ immune response,” the immunologist explained.

If those fail, Dr Iwasaki added, our adaptive immune system, which provides specific antibodies to fight the disease, comes online: though these antibodies can take “a few days or weeks to emerge.”

That last stage is triggered by infection or vaccines, hence the microbiologist’s comments earlier.

In fact the BBC says most symptoms of a cold “aren’t actually caused by the virus itself. Instead, they’re triggered by your own body, on purpose: they’re part of the innate immune response.”

So truly “boosting” these would more likely lead to a runny nose or muscle aches (a little like some people experience after a vaccine) than glowy skin or a sniffle-free winter.

“Vitamin supplements aren’t beneficial to your immune system unless you are deficient,” Dr Iwasaki shared.