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It’s not plant-based, but it is one of the few foods that provides vitamin D, which plays a huge role in regulating your immune system, says Jennifer McDaniel, owner of McDaniel Nutrition
Therapy in Clayton, Missouri. A 2020 study published in the journal _JAMA Network Open_ found that people who had untreated vitamin D deficiency were almost twice as likely to test positive
for COVID-19 as patients who had sufficient levels of the vitamin. A 6-ounce salmon filet has about 600 international units (IU) of vitamin D, which is close to the 800 IU that is
recommended daily for people 70 and older. Another bonus: It’s rich in omega-3 fatty acids, which have also been shown to strengthen your immune system. If you’re not a fan of fish,
McDaniel suggests marinating it in brown sugar and Dijon mustard for 45 minutes, then throwing it on the grill. “It mellows out that fishy taste, and it gives it a smoky flavor,” she
explains. Canned salmon counts, too: Throw it over a salad for a quick meal, she says. 7. GARLIC It’s rich in a compound called alliin, which may be the source of its immune-boosting
properties, notes Libby Mills, a Philadelphia-based nutritionist. A 2020 review published in the journal _Medical Hypotheses_ found that garlic itself seems to stimulate cells related to
immune system function. Another study published in the _Journal of Nutrition_ found that people given about 2½ grams of aged garlic extract for 90 days not only had higher levels of immune
system cells, but they also had fewer symptoms of cold and flu, and missed fewer workdays due to these respiratory illnesses, than a control group. At the very least, if you eat enough of
it, you’ll probably keep people away from you, Mills jokes. Although there’s probably not enough research to support taking a garlic supplement, Mills recommends that you cook with it in the
colder winter months. You can make your own pasta sauce with tomatoes and garlic, since vitamin C (found in tomatoes) is itself an antioxidant that helps the immune system she says. 8.
KEFIR Research, including a 2021 study published in _Biomedicine & Pharmacotherapy_, suggests that certain compounds found in fermented dairy such as kefir (which is like a thin yogurt)
have anti-inflammatory properties that can help the immune system fight viral infections. The probiotics found in kefir and other fermented foods also help to calm chronic inflammation,
according to Harvard Health. “Fermented dairy is rich in probiotics, which seem to have a positive effect on the immune system,” Mills explains. _Editor's Note: This story, published
Nov. 1, 2021, has been updated to reflect new information. _ Video: What to Know About the High Dose Flu Shot