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To protect those they love from a virus that can kill, people online are flooding the internet with search results for the best vitamins, foods, and activities to boost your immune system against coronavirus COVID-19 and its variants, like Omicron and Delta.
The internet provides plenty of answers—some reliable, others not.
The nutrients that seem to relate to immunity include vitamins A, C, D, and E, and the minerals zinc, selenium, and magnesium, according to an article edited by MedicineNet medical editor Melissa Conrad Stöppler, MD.
"There are no special diets, or particular foods, that will directly boost your immune system," their online statement says.
At the same time, many studies show that without enough of the essential nutrients your body needs, your immune system suffers. This includes studies showing that deficiencies of vitamins C and D are more commonly found in people with infections, including pneumonia.
"Your immune system and body can't function at their best without the basic building blocks they need to work properly," according to the article reviewed by Dr. Stöppler.
Eating a diet of fresh, whole foods in reasonable amounts is the best way to get your daily dose of vitamins, including the healthy antioxidants found in fruits and vegetables.
The important thing is variety, according to dietician Kathleen Zelman, MPH, RD/LD.
"Unless you eat a wide variety of foods, you may be missing out on important vitamins, minerals, and other nutrients," she writes.
In particular, she recommends the antioxidants otherwise known as vitamins A, C, and E, as well as the "sunshine" vitamin, vitamin D, and the mineral selenium.
"A diet rich in antioxidants has been linked to a host of health-promoting, disease-fighting activities in the body," she writes.
Antioxidant-rich foods include:
- Vitamin A and beta-carotene: pumpkin, squash, carrots, spinach, sweet potatoes, cantaloupes, dark leafy greens, and mangoes
- Vitamin C: citrus fruits, strawberries, bell peppers, cauliflower, broccoli, tomatoes, sweet potatoes, and asparagus
- Vitamin E: vegetable oil, almonds, whole grains, wheat germ, sweet potatoes, and yams
- Selenium: salmon and haddock
Sometimes food cannot provide enough of a certain nutrient. In these cases, supplements can be useful in supporting your natural immunity.
But which should you choose?
Sometimes it comes down to details. How much are you taking? What quality of supplement are you using? Not all supplements are of high quality, or even contain the ingredients they claim to.
"The U.S. Food and Drug Administration (FDA) does not determine whether dietary supplements are effective before they are marketed," the FDA warns on its website. "Therefore, advertised claims for some supplements might not be backed by scientific evidence."
Some evidence shows vitamins C, D, E, and zinc supplements are beneficial for respiratory infections with symptoms similar to COVID-19's, although no major studies have been published on their effects on the novel coronavirus.
Zinc in sufficient amounts has shown some evidence of reducing the length of some viral infections when taken right away. Studies have shown this using zinc lozenges, syrups, and tablets.
The NIH notes that the body needs zinc to create white blood cells that fight infections. However, overdoses can do more harm than good, and this along with all supplements should be taken with the consent of your doctor.
Vitamin C was put into a phase 2 clinical trial at one Chinese hospital during the outbreak. Researchers hope that as an antioxidant, the vitamin may reduce the lung inflammation COVID-19 can cause, a symptom that may lead to death.
Although most people who eat a typical Western diet get plenty of most nutrients, vitamin D has recently stood out as an exception, says dietician and MedicineNet medical author Betty Kovacs Harbolic, MS, RD.
"Vitamin D deficiency and insufficiency is now a global public health problem affecting an estimated 1 billion people worldwide," she writes. She goes on to point out that some people who are deficient in vitamin D are more prone to infection.
Since you only get about 20% of your needed vitamin D from food, Kovacs Harbolic says you should get the rest from sunshine (which provides vitamin D naturally) and supplements.
To get your vitamin D levels right, Kovacs Harbolic describes an ongoing process with your doctor. She recommends following your healthcare provider's instructions, as well as regular bloodwork monitoring to check your levels.
She also recommends the following foods as good sources of vitamin D:
- 1 tsp cod liver oil has 400 to 1,000 IU/vitamin D
- 3.5 oz salmon, fresh (wild) has 600 to 1,000 IU/vitamin D
- 3.5 oz salmon, fresh (farmed) has 100 to 250 IU/vitamin D
- 3.5 oz sardines, canned has about 300 IU/vitamin D
- 3.5 oz tuna, canned has 236 IU/vitamin D
- 3.5 oz shiitake mushrooms (fresh) has about 100 IU/vitamin D
- 3.5 oz shiitake mushrooms (sun-dried) has about 1,600 IU/vitamin D
- 1 egg yolk has about 20 IU/vitamin D
- 8 oz fortified milk or yogurt has 100 IU/vitamin D
- 8 oz fortified orange juice has about 100 IU/vitamin D
- 3 oz fortified cheese has about 100 IU/vitamin D
If you decide to get your vitamin D as a supplement, how you eat it makes a big difference.
"What you take is as important as how you take it," Kovacs Harbolic said. "Vitamin D supplements should be taken with a meal that contains fat. Studies have shown that when taken on an empty stomach versus with a meal containing fat, there was an average of 32% more vitamin D absorption in the fat-containing meal."
The scientific evidence is fairly clear—your body needs adequate vitamins and minerals to maintain your immune defenses against a wide variety of infections, including COVID-19. But what counts as adequate? And how do you know if you have enough?
The National Academy of Sciences establishes national nutrition recommendations. These are the same standards you find listed on the labels of foods sold in US grocery stores. While researchers broadly agree that you need enough of these essential nutrients, some claim you can get additional benefit from consuming more than that in some cases. This claim is more controversial.
"In research on the incidence of infections in nursing homes, vitamin E was protective," Simin Nikbin Meydani, PhD, senior scientist and director of the Tufts' HNRCA Nutritional Immunology Laboratory said in a recent newsletter.
She went on to warn that more is not necessarily better. She pointed out that in studies, 200 mg of vitamin E was found to be ideal, but more than that added no more protective benefit.
Along with a healthy diet and adequate nutrition, there are healthy activities that can re-enforce your immune health too.
Solo exercises include jogging, jumping rope, and a variety of at-home workouts from yoga to HIIT. Some prefer gardening, which can also be great exercise.
Moreover, chronic stress has been shown in some studies to leave us more vulnerable to infections. An article reviewed by Dr. Stöppler explains:
"Being stressed out leads to increased levels of suppressor T cells, which suppress the immune system. When this branch of the immune system is impaired, you are more susceptible to viral illnesses including respiratory conditions like colds, flu, and the novel coronavirus infection."
You can reduce stress through breathing exercises, meditation, working out, talking to a therapist, and getting out into nature, along with many other ways.
Getting the right amount of quality sleep can help your natural infection resistance, too. Several studies confirm the link between sleep and a healthy immune system. For most adults, that means 7 to 9 hours of uninterrupted slumber.
If you find it difficult to get this much, you can try to improve your "sleep hygiene" by waking up at the same time each day, avoiding alcohol and caffeine in the evening, and following a bedtime routine you find relaxing.