The four steps discussed here will show you how to prevent colds and how to fight off flu symptoms.

© Jean Paul Chassenet

When I was a student, I used to get sick every Christmas break. I’d make it through the stress of midterm exams in mid-December and be looking forward to a two-week break from school. Then—voila—I’d come down with a nasty cold or the flu and be miserable for a good portion of my vacation. I wish I would have known then what I know now—there’s much we can do to decrease our chances of getting colds and flus. Below you’ll find a list of well-researched strategies that you can start using now for how to prevent colds and flu season. Most cold and flu symptoms strike between October and May, so now is the perfect time to start using these tips._[1] (See also our post Common Cold and Flu Prevention: Tips to Keep You Healthy.)

How to Prevent Colds and Flu: 4 Strategies

1. Micronutrients

Poor nutritional status is the most common cause of compromised immunity._[2] It can lead to deficiencies in the vitamins and minerals that are required for proper immune function, and can impair phagocytic function. Phagocytes are the immune cells that destroy cold and flu viruses. Without adequate nutrients, your immune system can’t do its job.

Micronutrient inadequacies are surprisingly common in the general U.S. population so it is vitally important to eat a nutrient-dense diet. Skip the nutrient-poor foods (especially foods made with added sugar and refined grains) and choose those full of immune-boosting vitamins and minerals instead.

2. Get Crucial Vitamins and Minerals for Immune Function

The vitamins and minerals that play critical roles in immunity are:

• Vitamin A. Highest in beef liver and cod liver oil, eggs, butter, and whole milk. Sweet potato, pumpkin, carrot, spinach, kale, and butternut squash are high in beta-carotene which converts to vitamin A.
• Vitamin C. Highest in citrus fruits, strawberries, red peppers, tomatoes, papaya, broccoli, and Brussels sprouts.
• Vitamin D. Naturally highest in salmon, mackerel, sardines, cod liver oil, egg yolks, and shitake mushrooms.
• Vitamin E. Highest in nuts and seeds, olive oil, and avocado.
• Vitamin B6. Naturally highest in salmon, tuna, turkey, chicken, beef, liver (poultry and beef), Russet potatoes with skin, and pistachios.
• Folate. Naturally highest in legumes, asparagus, spinach, turnip greens, and broccoli.
• Vitamin B12. Highest in crab, mussels, mackerel, beef, lamb, salmon, sardines, tuna, cod, and scallops.
• Zinc. Highest in oysters, beef, lamb, pork, turkey, chicken, sesame seeds, pumpkin seeds, and legumes.
• Iron. Highest in liver and other organ meats, red meats (beef, lamb, pork, etc.), fish and shellfish, poultry, legumes, and tofu.
• Selenium. Highest in brazil nuts, fish and seafood, red meats, poultry, shitake and other mushrooms, and asparagus.
• Copper. Highest in beef liver, shellfish, nuts and seeds, legumes, shitake mushrooms, seaweed, and kale.
• 

3. Flavonoids

In addition to the vitamin and mineral micronutrients, certain phytonutrients, especially flavonoids, are excellent for enhancing immune function. To get them, eat a wide variety of fruits, vegetables, and other plant foods, including berries—which have antiviral effects._[16]

If fresh or frozen berries are not available or in your budget, consider berry concentrates and extracts in liquid, powder, or solid extract form (such as Mixed Berry Solid Extract from Wise Woman Herbals or ProBerry-Amla by Nutricology).

4. Probiotics, The Surprising Immune System Booster

Most people think of zinc, vitamin C, and echinacea for prevention of colds and flu long before they think of probiotics. But the research is just as strong (or stronger) for probiotics as a preventive treatment than it is for these more commonly mentioned compounds.

Numerous clinical studies show that probiotics can enhance the immune system to help prevent viral respiratory tract infections such as the common cold._[5-8] A study in healthy adults found that a combination of Lactobacillus plantarum and Lactobacillus paracasei reduced the risk of getting a cold and strengthened the subjects’ immune defenses by boosting B-lymphocytes, immune cells that thwart viruses._[15]

If you do come down with a cold or flu, studies show that probiotics tend to reduce the severity and duration of symptoms._[5,9-11] They also may be able to directly kill viruses that attack the respiratory tract._[4] Probiotics are effective in a variety of populations, from children in daycare to stressed-out college students, elite athletes, and the elderly._[12-14]

Summary: Quick Steps to a Cold-Free Winter

So here are two quick actions you can take now that will give you a great chance of going through the entire winter cold- and flu-free:

1. 1. Buy nutrient-dense foods that you enjoy and add some news ones to your shopping list. Add some fresh or frozen berries—strawberries, blueberries, raspberries, elderberries, pomegranate—or take a berries extract supplement.
   2. Add probiotics to your daily routine by either eating foods such as yogurt, kombucha, and sauerkraut or by taking a daily probiotic supplement.

Start these simple measures now to stay healthy all winter long.

1. CDC. Influenza (flu). Accessed August 3, 2015.
2. Clin Infect Dis. 2008;46(10):1582-8.
3. USDA. 2005. What We Eat In America, NHANES 2001-2002: Usual Nutrient Intakes from Food Compared to Dietary Reference Intakes.
4. Eur J Clin Microbiol Infect Dis. 2014 Aug;33(8):1289-302.
5. Cochrane Database Syst Rev. 2015 Feb 3;2:CD006895.
6. Nutr Hosp. 2011 Jan-Feb;26(1):228-35.
7. Int J Clin Pharmacol Ther. 2005 Jul;43(7):318-26.
8. Anaerobe. 2010 Jun;16(3):195-200.
9. Clin Nutr. 2005 Aug;24(4):481-91.
10. Am J Clin Nutr. 2015 Jun;101(6):1188-96.
11. Am J Infect Control. 2013 Dec;41(12):1231-5.
12. Expert Opin Biol Ther. 2015 Jan;15(1):9-20.
13. J Sci Med Sport. 2014 Jul;17(4):356-60.
14. Br J Nutr. 2013 May 28;109(10):1856-65.
15. Eur J Nutr. 2011;50(3):203-210.
16. J Sci Food Agric. 2013 Jul;93(9):2239-41.

Originally published in 2016, this post is regularly updated.