It's flu season, and colds and new Covid-19 variants are still spreading, so, you'd be wise to keep your immune system top of mind.

And while it's important to build up your defense against illness during the winter months, it's actually something you should be doing all year round, according to Dr. William B. Miller Jr., an infectious disease expert and evolutionary biologist.

"The only effective way to really boost your immune system is to adopt a steady rhythm," says Miller, author of "Bioverse: How the Cellular World Contains the Secrets to Life's Biggest Questions."

"You can't just say, 'Well, I'll be good in the winter and bad in the summer.' It doesn't work that way. It disrupts cells and takes them a long time to get back to their normal pattern of behavior."

To efficiently bolster your immune system, you should work in partnership with your cells, Miller tells CNBC Make It. Here are a few practices he recommends to help you be the best partner possible.

6 ways to boost your immune system

Miller encourages you to implement these behaviors throughout the year to increase your immune resilience:

1. Eat foods high in fiber like berries and avocados, or take probiotics/prebiotics: gut health can greatly impact your immune system
2. Reduce sugar intake
3. Exercise regularly
4. Get sufficient hours of sleep
5. Lower alcohol intake
6. Don't smoke or consume drugs (that aren't prescribed to you for medical reasons), as these activities can weaken your immune system

Why it's important to bolster your immune system

Aside from the more obvious reasons, there are other great benefits to having a strong immune system.

"Healthy aging is almost exactly equivalent to a strong immune system," Miller says. Likewise, weaker immune systems typically equate to a shorter life, he adds.

But the advantages of having great immune resilience aren't limited to just physical health, according to Miller.

"A strong immune system translates into lower incidence of mood disorders, lower depression rates, better sense of well-being [and] higher degrees of optimism," he says.

"These kinds of benefits are derived because our individual cells, including our microbes, influence our behaviors."

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