Our immune system protects us from pathogens that can leave us vulnerable to getting sick. We often think of a weakened immune system in relation to catching a cold or getting the flu or COVID. However, a weakened immune system can also lead to more serious conditions like allergies, asthma, and autoimmune diseases.
When possible, it is always best to get your vitamins and minerals from foods rather than supplements. However, you should talk to your healthcare provider or nutritionist to see if you may need extra supplementation of certain nutrients. If you do need to take a supplement, be sure you are taking a high-quality supplement from a reputable and well researched source.
Here are the Top 5 Nutrients that help keep your immune system strong.
Vitamin A (1,2)
Most known for its role in eye health, this vitamin is also critical for the immune system by supporting the function of macrophages and other cells if the innate immune system. It can also regulate inflammation and the function of B cells and T cells, which are part of the adaptive immune system.
Vitamin A is found in two forms:
Preformed A: Present in animal sources of foods, such as fish, organ meat, and dairy
Provitamin A carotenoids: Present in plant foods, including greens, red, yellow and orange vegetables.
Supplements: it is important to know the course of vitamin A contained in a supplement. Preformed vitamin A (retinols and retinyl esters) can cause unwanted effects and can be toxic in high amounts. Provitamin A carotenoids, like beta-carotene does not have toxic effects nor an upper limit establish for intake.
Food sources: It is best to get a variety of animal and plant-based sources of vitamin A such as beef liver, dairy, cheese, eggs, carrots, sweet potato, pumpkin, cantaloupe, squash, red peppers, and mango.
Just 1 small, baked sweet potato contains 156% of daily requirements for vitamin A!
Vitamin C (3)
Vitamin C is an essential nutrient, meaning the body cannot make it, therefore it must be consumed in the diet. It is most commonly known for its antioxidant and immune functions, thought it provides several other benefits to the body such as helping with the production of collagen, neurotransmitters, protein metabolism, and the absorption of non-heme iron (plant sources of iron). Studies suggest taking/consuming 200 mg per day of vitamin C can help reduce cold symptoms and duration.
Supplements: Doses above 1,000 mg have been noted to have poorer absorption rates (up to 50% less!), therefore, it can be ideal to take 500 mg or less per serving.
Food Sources: Vitamin C is found in almost all fruits and vegetables but the highest amounts can be found in citrus fruits (oranges, grapefruit), leafy green vegetables (like spinach & kale), tomatoes, bell peppers, Brussel sprouts, strawberries, papaya, broccoli and kiwi.
Just ½ cup of red sweet peppers provides 95 mg of Vitamin C!
Vitamin D (1,4)
Vitamin D is a fat-soluble vitamin that is found in some foods but is also produced endogenously from sunlight exposure, hence why it is sometimes called the “Sunshine Vitamin”. This vitamin, which is also a hormone, helps the body fight against infections through regulatory processes of the cells of the innate and adaptive immune systems. Many studies suggest adequate vitamin D intake and serum levels in the body help protect against seasonal immune conditions (cold, flu, pneumonia, and respiratory tract infections). But this is just part of the beauty of vitamin D—in reality, the benefits and functions of vitamin D are too much to list in this post!
Supplements: It is ideal to supplement this in a dose that is reflective of your needs as determined by testing (25-OHD). Vitamin D2 must be converted to Vitamin D3, which is the active form that can be more efficiently utilized by your body.
Food sources: Fatty fish (salmon, mackerel, tuna, sardines), mushrooms, eggs, fish liver oils, and some fortified foods.
Just one serving of salmon (3 ounces) provided 570 IU of vitamin D.
Vitamin E (5,6)
Vitamin E refers to a collection of fat-soluble compounds that naturally occur in multiple forms, including tocopherols and tocotrienols. Vitamin E is a powerful antioxidant like Vitamin C and plays a role in the immune system by supporting the proper function of white blood cells (to fight infections) and reducing oxidative stress, lowering inflammation and overactivity of the immune system.
Supplements: Deficiency in vitamin E is not common, therefore it is best to consume vitamin E from food sources. Further, some medications may be contraindicated with supplemental use, so we recommend speaking to your healthcare provider or nutritionist before beginning a vitamin E supplement.
Food Sources: Good sources of alpha-tocopherol include nuts and seeds, particularly almonds, peanuts, hazelnuts, and sunflower seeds. Other food sources include wheat germ oil, spinach, broccoli, and kiwi. Of note, most vitamin E consumed in the standard American diet comes in the gamma-tocopherol form from soybean, canola, and corn oils.
Just 1 ounce of sunflower seeds provides nearly half the daily requirements!
Zinc (1,7)
Zinc is a mineral involved in over 100 enzymatic processes in the body. Zinc has anti-viral and anti-inflammatory properties and has the ability to support the cells of the immune system, such as natural killer cells. YUP—as the name implies, these cells are defenders in your body seeking and destroying harmful invaders!
Supplements: Zinc deficiency is not common, but it doesn’t mean some people will not benefit from supplementation because of the many processes it is involved in. Check with your provider to determine if this is appropriate for you. Some providers offer a “zinc tally test” which can be an easy way to assess your needs.
Food sources: The best sources of zinc are seafood, meal, and fish, such as crab, shrimp, and lean meats (beef, poultry), as well as other foods including lentils, yogurt, and cheese.
The richest source of zinc is oysters!
Just 3 ounces of oysters provides 28-32 mg of zinc!
(The next best source is beef at 3.8 mg)
Conclusion
Ultimately, nutrients work collectively in the body to ensure it is operating optimally so a well-balanced nutrient intake that reaches the Recommended Daily Allowances (RDAs) is a great starting point. If you are unsure how your current dietary intake stacks up, tracker your food intake for 3-7 days using a program like Cronometer to see if you are reaching those RDAs.
Disclaimer: Individual needs of nutrients will vary. Please speak with your health care provider or nutritionist for your personalized recommendations.
References
1. National Institute of Heath Office of Dietary Supplements. National Institutes of Health Office of Dietary Supplements. 2023 [cited 2024 Sep 18]. Dietary Supplements for Immune Function and Infectious Diseases: Health Professional Fact Sheet. Available from: https://ods.od.nih.gov/factsheets/ImmuneFunction-HealthProfessional/
2. National Institutes of Health Office of Dietary Supplements. National Institutes of Health Office of Dietary Supplements. 2023 [cited 2024 Sep 18]. Vitamin A and Carotenoids: Fact Sheet for Health Professionals. Available from: https://ods.od.nih.gov/factsheets/VitaminA-HealthProfessional/
3. National Institute of Health Office of Dietary Supplements. National Institute of Health Office of Dietary Supplements. 2021 [cited 2024 Jul 2]. Vitamin C Fact Sheet for Healthcare Professionals. Available from: https://ods.od.nih.gov/factsheets/VitaminC-HealthProfessional/
4. National Institute of Health Office of Dietary Supplements. National Institute of Health Office of Dietary Supplements. 2023 [cited 2023 Sep 26]. Vitamin D Fact Sheet for Health Professionals. Available from: https://ods.od.nih.gov/factsheets/VitaminD-HealthProfessional/
5. National Institute of Health Office of Dietary Supplements. National Institute of Health Office of Dietary Supplements. 2021 [cited 2024 Jul 2]. Vitamin E Fact Sheet for Healthcare Professionals. Available from: https://ods.od.nih.gov/factsheets/VitaminE-HealthProfessional/
6. Lee GY, Han SN. The role of vitamin E in immunity. Vol. 10, Nutrients. 2018. doi: 10.3390/nu10111614
7. National Institutes of Health Office of Dietary Supplements. National Institutes of Health Office of Dietary Supplements. 2022 [cited 2023 Sep 26]. Zinc Fact Sheet for Health Professionals. Available from: https://ods.od.nih.gov/factsheets/Zinc-HealthProfessional/