In the bone-chilling cold, your nose might run faster than you do, and the flu seems keener to snuggle with you than your significant other. Often the go-to reaction is to throw money at the so-called "immunity-boosting" potions. Most of which, end up being no more useful than a cucumber at a fruit party. It's not surprising though since the supplement industry is as regulated as crowd control at a free beer event, resulting in inflated claims and depleted pockets. With the supplement market reaching a fantastical $31 billion in the US in 2018, it seems there's no loss of believers in these magic pills.

So how do we separate the wheat from the chaff and make intelligent supplement investments? We turned to dietitians, those sensible nerds who believe in evidence more than leprechauns. Here’s what they holster in their arsenal in the battle of Man vs Virus.

The undisputed champion - Vitamin D. Unlike a bad politician, it delivers on its promises, like fighting off infections, assisting with calcium absorption, and bone health, according to our hard-nosed dietitian friend Brittany Scanniello. Fellow dietitian Melissa Azzarro also swears by Vitamin D in the cold months when the sun is as rare as self-discipline in a donut shop. She believes it keeps the immune system in ship-shape and bristol fashion.

Following closely is Vitamin C and zinc lozenges, useful grunts in fighting cold, but not preventing it (despite what your grandma may believe). They can sling mud at the cold and reduce its duration. Just be careful not to overdose on zinc if you're already taking multivitamins - one too many soldiers does not always win you the war.

Melissa Nieves stocks green tea, no it's not a supplement, but apparently, it’s full of mean antioxidants that punch the daylights out of flu viruses. Likewise, the humble garlic, more often loved for keeping vampires at bay, has disease-fighting properties, perhaps useful if you don’t want to smell like a pizza joint everyday, try an allicin-containing garlic supplement - Scanniello does, from October through April.

When sick, Azzarro gives a thumbs-up to elderberry, supposedly helpful in reducing flu symptoms. And sneaking in the list is the unassuming probiotics, constant companions for Whitney Gingerich during the sniffle season. Certain strains of these live bacteria have been observed to offer therapeutic potential for viral infections.

Scanniello isn’t done yet and throws in a wild card – medicinal mushrooms. She claims they positively impact our immune systems, stimulate it when there's something to fight, and works best combined as a daily blend in her smoothie.

So there you have it, the truth behind the curtain of health supplements. Of course, always consult with your friendly neighborhood healthcare provider before embarking on your own regiment of pills and potions. Remember, knowledge is the best supplement, and it's free.