Staying healthy during the winter months can be a challenge, especially amidst a particularly rough cold and flu season. And while research remains limited for how much supplements can actually help, there is some early evidence to suggest that some may be able to support your immunity during the colder months.

1. Zinc

Several studies have shown zinc can shorten the duration of colds and minimize their intensity if taken within 24 hours of symptom onset.

Zinc helps block viruses from multiplying in the nose and throat and supports the development and function of important immune cells, including T cells and natural killer cells, said Shruti K. Gohil, MD, a board-certified infectious diseases specialist and the associate medical director for UCI Health Epidemiology and Infection Prevention.

When sick with a cold, you should take 75-90 mg per day (divided every 2-3 hours). For daily immune maintenance, Gohil said 15-30 mg per day is sufficient.

Just don’t overdo it. “Signs of zinc toxicity are very similar to the symptoms of the common cold,” said Jacqueline Vernarelli, PhD, an associate professor and the Master of Public Health program director at Sacred Heart University.

2. Vitamin D

Vitamin D deficiency is linked to increased risk of respiratory infections. “Though we can get it from the sun, our sun exposure is limited in the winter months, so taking a supplement is important in northern climates,” Vernarelli said.

Gohil added that Vitamin D supports “innate immunity,” which is the body’s first line of defense, including the protective lining of the respiratory tract.

“These immune cells have vitamin D receptors that control the ability to make natural antimicrobial substances that can defend the body against germs,” Gohil said. “It also regulates the immune response to be effective but not excessive.”

Some studies have shown fewer respiratory infections when people who have low vitamin D levels take supplements regularly.

Gohil said to aim for 1,000-2,000 IU per day, preferably with a meal containing fat for ideal absorption, while higher doses may be needed for those who are deficient.

3. Vitamin C

Vitamin C enhances the function of two critical cells of your immune system—white blood cells and neutrophils. Both use vitamin C rapidly when fighting infections. It is also an important antioxidant, as it removes free radicals produced when your body fights infection, said Gohil.

Like zinc, studies have shown shorter duration and reduced severity of colds when taken consistently. You should aim for 500-1,000 mg once or twice per day when sick and 200-500 mg per day for prevention.

“People with a history of kidney stones should consult their doctors before using a supplement as vitamin C in excess can increase the risk of stones in some patients,” Gohil noted.

4. Probiotics

While you may not associate probiotics with a strong immune system, Vernarelli said a healthy gut is the foundation of a healthy immune system.

“The microbiome in the gut helps to support our immune function and a probiotic will help to keep the microbiome balanced,” she said. “Foods like yogurt and dairy-free yogurts, fermented foods like kimchi and sauerkraut, and probiotic supplements are your best bets.”

5. Elderberry

Elderberry may directly reduce viral replication and may prevent a virus from attaching and entering human cells, Gohil said. It may also stimulate the production of signalling molecules, which help fight infection.

Several small randomized controlled trials have shown that elderberry reduced the duration and severity of flu symptoms when taken within 24-48 hours of symptom onset. However, data on dosing strategy and the effectiveness of long-term use to prevent infection are lacking.

6. Echinacea

Echinacea may help support and regulate immune responses and reduce inflammation which can shorten and reduce symptoms when taken early, Gohil said.

However, study results have been mixed on its effectiveness, and there’s not enough research on its dosing strategy.

What Else to Know

Before you turn to dietary supplements, the most effective winter “supplement” is plain old soap, said Vernarelli.

“The best way to prevent infection is to wash your hands with warm soapy water whenever you come in from errands, home from school, or before you eat or drink,” she said.

It’s also important to note that evidence supporting supplement effectiveness is still evolving, and the available data is limited.

“It is critical for patients to understand that supplements are not substitutes for vaccines, antivirals when indicated, or hydration,” Gohil said. “Supplements are also not a substitute for healthy meals. Vitamins and minerals obtained through food are more easily absorbed by the body.”