As people around the world cope with the coronavirus pandemic, we find ourselves asking whether there are any particular foods we can eat to boost our body’s natural defense system. While regular hand washing and self-isolating have now become part of our daily routines, there are several key nutrients we can focus on, which support a strong and healthy immune system.
Protein
Immunity Functions:
Amino acids (the building block of protein), play an important role in immune response by activating the “killer” cells that destroy bacteria and harmful cells
Amino acids regulate the production of antibodies, which are proteins in the blood that bind to specific invaders, such as germs, viruses, or tumor cells. Without antibodies, bacteria and viruses would be free to multiply in the body
Recommended Daily Amount (RDA):
Adults 18+ years: 0.8 grams/kg body weight
More is needed during pregnancy, lactation, illness, sports, and advanced age
Plant-based (missing 1 or more essential amino acid): Nuts, seeds, whole grains, beans, lentils
Supplemental Facts:
Protein supplements are generally not needed because most Americans consume more than the RDA
Ensure you eat a variety of protein sources from the options listed above
Vitamin C
Immunity Functions:
Our bodies cannot make the vitamin; therefore, we must obtain it from food
Serves as an antioxidant that fights against free radicals in the body
Stimulates white blood cells at the site of infection and enhances microbial killing
Helps prevent or delay certain cancers and heart disease, promote healthy aging, and prevent and treat respiratory and full-body infections
Vitamin C intake cannot prevent a common cold; however, some evidence shows that doses of >200 mg/day may decrease the length or severity of symptoms by >1 day. Taking Vitamin C after symptoms begin does not appear to be beneficial
Recommended Daily Allowance (RDA):
Men 19+ years of age: 90 milligrams
Women 19+ years of age: 75 milligrams
Dietary Sources of Vitamin C:
Citrus fruits such as oranges, grapefruit and tangerines, red/yellow bell peppers, papaya, strawberries, berries, cantaloupe, tomatoes, broccoli, cherries, guavas, spinach, kale, kiwis
Supplemental Facts:
Make sure to look at the labels of Vitamin C boosting products such as: Emergen-C, Ester-C, and Airborne. They often contain syrups, added sugar, dyes, and other additives
Vitamin C is a water-soluble vitamin, meaning the body does not store it. This is particularly important for those who overload on supplements, for the body will just excrete any excess via the urine
Always ensure you obtain Vitamin C through food sources first, before resorting to a supplement
Probiotics
Immunity Functions:
Live microorganisms or “good” bacteria that support a healthy microbiome
Inhibit the growth of harmful microorganisms in the GI tract, neutralize toxins, produce cytokines(messenger molecules that help immune cells work together against an infection)
A 2015 evaluation of 12 studies with 3,720 total participants found that people taking probiotics may have fewer and shorter upper respiratory infections. However, the quality of evidence was low. Lactobacillus and Bifidobacterium have the strongest antiviral activity against respiratory viruses, particularly influenza virus type A
Recommended Daily Allowance (RDA):
More research is needed on the recommended dosage, however 1 – 10 billion colony-forming units (CFU)— the amount contained in a capsule or two — can be safely taken several days per week
Dietary Sources of Probiotics:
Cultured dairy products such as yogurt and fermented foods such as: kimchi, kombucha (a fermented tea), sauerkraut (fermented cabbage), miso (a fermented soybean-based paste), and raw unfiltered apple cider vinegar
Supplemental Facts:
Always ensure you obtain probiotics through food sources first, before resorting to a supplement
Supplements can be found in different forms. Ensure the supplement has a variety of bacterial strains and does not include any additives
Vitamin A
Immunity Functions:
A fat-soluble vitamin that helps protect against infections by keeping skin and tissues in the mouth, stomach, intestines, and respiratory system healthy
Beta-carotene is an antioxidant which protects cells from free radical damage
Involved in the production and function of white blood cells, which help capture and clear bacteria and other pathogens from your bloodstream
Recommended Daily Amount (RDA):
Men 18+ years of age: 900 micrograms
Women 18+ years of age: 700 micrograms
Dietary Sources of Vitamin A:
Sweet potatoes, carrots, broccoli, spinach, red bell peppers, squash, pumpkin, cantaloupe, apricots, mangoes
Always ensure you obtain Vitamin E through food sources first, before resorting to a supplement
Vitamin D
Immunity Functions:
A fat-soluble vitamin naturally produced in the body via sun exposure
Can help reduce the risk of acute respiratory infections, including colds and flu, particularly among people who are severely deficient or those with little exposure to sunlight
Immune cells (B and T cells) from multiple autoimmune diseases appear to respond well to Vitamin D
Recommended Daily Amount (RDA):
Adults 19-70 years of age: 600 IU
Adults 71+ years of age: 800 IU
Upper limit: 4,000 IU/day
Dietary Sources of Vitamin D: there are very limited food sources of Vitamin D, so it is important to incorporate them as frequently as possible
Fatty fish such as: salmon, tuna, mackerel, swordfish, cod liver oil, dairy (choose non-fat options): milk, yogurt, cheese, beef liver, mushrooms exposed to UV light for at least 10 minutes, and fortified non-dairy milks and 100% orange juice
Supplemental Facts:
Vitamin D is made from cholesterol when your skin is exposed to the sun’s UVB rays. Spend 10-30 minutes in the sun daily without sunscreen, then immediately apply sunscreen. The best time of day to get sun is midday 10AM-3PM
At nutritional doses Vitamins D2 and D3 are equivalent, but at higher doses Vitamin D2 is less potent. If you need purchase a supplement, choose Vitamin D3
Always ensure you obtain Vitamin D through food sources first, before resorting to a supplement
Zinc
Immunity Functions:
A mineral that helps the immune system fight off invading bacteria and viruses
There is no evidence that zinc doses >100 mg/day leads to better treatment of the cold. However, taking zinc at the beginning of a cold may shorten its duration
Zinc is best absorbed from animal sources. Foods such as whole-grains and legumes have phytates, which bind to zinc and inhibit its absorption
Supplemental Facts:
Aside from vegetarians and vegans, most Americans get enough zinc in their diet
Supplements may interfere with certain medications and could cause side effects such as loss of taste
Long-term zinc consumption over 40 mg/day for adults can result in copper deficiency
Always ensure you obtain zinc through food sources first, before resorting to a supplement
Other nutrients that support a healthy immune response include: Vitamin B6, Vitamin B12, copper, folate, selenium, and iron. Several herbs have also been linked to an increased immune response including: ginger, ginseng, elderberry, turmeric, and garlic. In addition to eating a diet rich in the immune-supporting nutrients listed above, ensure you sleep 7-9 hours a night and keep your stress levels to a minimum. By following these recommendations, you can help reinforce your body’s fight against infection and foreign invaders.
