As we find ourselves in the midst of yet another winter season during a global pandemic, the desire to maintain our immune system defenses are stronger than ever. While the winter weather, in itself, doesn’t bring along with it a bevy of colds and viruses, the elements that surround the season do. There are several reasons for this.

Not only are the days shorter and the nights longer, but there also tends to be more cloudy days decreasing your potential for a good dose of sunshine, explains functional nutritional therapy practitioner Tansy Rodgers, F.N.T.P. “This sunshine is important for our growth and mental wellbeing as well as the growth of colorful fruits and vegetables that are higher in antioxidants, vitamins A, B, C, and D,” she says. “When you are not being consistently exposed to sunshine and reaping the health benefits that that brings and you are not being exposed to as much varied, fresh produce chocked full of a variety of nutrients, it can be easy to hit some nutrient deficits that are critical to keep high for the winter months.”

Another immune system-concerning element brought on by the winter is the fact that we spend more time indoors, which significantly increases our risk of being exposed to contagious illnesses like the cold, flu and COVID-19. While being indoors for the majority of time during the winter months is somewhat inevitable, bolstering your immune system can help provide a layer of protection to shield you from certain illnesses.

The easiest way to boost your immune system is by consuming the right kind of nutrients. While food is the best way to glean these nutrients, supplements are a steady second. Here, nutrition pros share some of the best supplements you should be taking this winter.

Vitamin C

Easily the most famous supplement to help boost the immune system, vitamin C does a wonderful job of protecting the systems in your body. Not only does it help the immune system to fight off pathogens, but it is also considered an antioxidant helping the body fight off oxidative stress, explains Mary Opfer, MS, RDN, CDN, in Westchester County, New York. “A deficiency of vitamin C affects the immune system and increases susceptibility of infection,” she warns. “Immune health, wound health, repairs body tissue and contributes to healthy skin, and helps with absorbing iron.” You can get your fair share of vitamin C from oranges, red sweet peppers, collard greens, mustard greens, kale, citrus fruits and parsley.

For supplementation, Rodgers recommends 90 mg a day for men and 75 mg a day for women, with an upper limit of 2000 mg. “If you take a supplement, make sure that it is a whole food form so that your body is better able to absorb it,” she says. “Vitamin C is water-soluble, so taking too much will most likely not be harmful, however, taking too much could cause diarrhea and nausea.”

Zinc

Another supplement well-known for its immune-boosting benefits, zinc plays an important role in nearly every cellular function. “Zinc plays a role in protein and carbohydrate metabolism, cell division and growth, skin health, is vital for the immune health and it’s functioning and is also a key component in gut health,” says Rodgers. You can find zinc abundantly in oysters, red meat and poultry and can also supplement. “It is recommended that most adult men get 11 mg a day and most adult women take 8 mg a day, both with an upper limit of 40 mg. Some forms of zinc are more bioavailable than others, so if you try a supplement with a form that does not work for you, trying a different form of zinc may give you better results,” adds Rodgers.

Vitamin D

Also known as the “sunshine vitamin,” this supplement plays a crucial role during winter, when we are less exposed to the sun thanks to cold weather and shorter days. “Vitamin D is a key player in many functions of the body, assisting calcium absorption, boosting immune system function, bone development, healthy cell growth, reducing inflammation, activating areas of the brain critical for biorhythms, and proper neuromuscular function,” explains Rodgers.

Unfortunately, most Americans run low in this all-important nutrient, with an estimated vitamin D deficiency in the U.S. population of 41.6 percent, per research published in the journal Nutrition Research. The National Institutes of Health recommends 600 IU of vitamin D daily for most adults. While the best way to get this is by eating vitamin D-rich foods such as salmon, tuna, mushrooms, liver, and eggs, you can also supplement. Roger E. Adams, Ph.D., doctor of nutrition and owner of eatrightfitness, recommends 50-125mcg per day to his clients who are running low.

B Vitamins

B vitamins supplements are important during the winter months for many reasons. “Not only do they help to improve your mood, decrease depression, and decrease stress, but they are also a cofactor for proper digestion and a healthy gut and are needed for the body to make neurotransmitters such as serotonin,” says Rodgers. “This is important to know if you are under a lot of stress because B vitamins are essential for the cells to make energy and when the cells are continually being replenished, your energy may be boosted.” She recommends discussing the possibility of supplementing with B vitamins with your healthcare provider, especially if you are on certain medications that help treat depression.

Vitamin A

This important supplement is often associated with vision, however, Opfer notes that it also helps the immune system because it protects the mucus membranes of the skin and eyes. “It is considered an anti-inflammatory vitamin that is critical to helping or enhancing the immune system because vitamin A increases the activity of the immune system,” she says. Before supplementing with vitamin A, she recommends asking your healthcare provider to test you for a deficiency, as fat soluble vitamins can be toxic if taken in too high doses. Food sources of vitamin A include swiss chard, kale, winter squash and nectarines.

Fish Oil

This supplement oil comes from fatty fish, such as salmon, tuna, herring, anchovies and mackerel and offers a wide array of benefits for our health including reducing the risk of heart and eye diseases as well as mental disorders. That last one is especially important during winter, when your risk of mental illness is higher, per research published in the International Journal of Preventive Medicine. “If you do currently take an antidepressant, fish oil has been connected to possibly helping the antidepressant work better—and it doesn’t typically cause an interaction,” says Rodgers. “Taking about 1,000 mg EPA per day is typically recommended, but make sure that you take your fish oil with one of your biggest meals and/or one that contains some fat.”

Rhodiola

This supplement herb has long been used to help prevent colds and flu but has shown promise in research to aid in preventing mild forms of depression, fatigue and anxiety, notes Rodgers. It may also be helpful in reducing stress, which is something we could all benefit from, especially around the hectic holiday season. “Recommendations for taking rhodiola start with 150–200 mg daily of extract standardized to 3 percent rosavin and about 1 percent salidroside, the active compounds; using that for five to seven days and increasing the dose to 400-500 mg if necessary,” Rodgers says. “Most people need between 300 mg and 500 mg per day of the standardized extract.”

Probiotics

Did you know that about 70 percent of your immune system is located in your gut? This is a great indicator of how good-gut bacteria is vital for a healthy immune system, as well as for our bodies to function optimally. For this reason, Dr. Adams recommends supplementing with a quality broad spectrum probiotic year-round, but especially in the winter months to ensure our immune system is getting all the help it can get. “A typical dose would be 1-10 billion CFU per dose, but some of the more concentrated ones may be up to 50 billion CFU or more,” he says.