As many of us prepare to send our children back to school and with Covid-19 showing no sign of abating, I’m getting requests for tips on how to keep kids’ immune systems in good shape this fall. The good news is, kids are probably less likely than usual to get the standard sniffles this semester due to enhanced cleaning protocols, social distancing, and masking measures in place to prevent the spread of Covid-19. However, their immune systems may be a little out of practice after a year and a half of relatively sterile living (e.g. limited contact with peers and endless hand sanitizing). Thankfully, kids are at very low risk of serious illness from SARS-CoV2, and masked exposure would reduce the viral load, which may mean a milder or asymptomatic case (1).
Aside from these external prevention strategies there are a few key nutrients that support healthy immune defenses and may offer an additional layer of protection (to be clear, I am not claiming that diet and supplements can prevent or cure Covid-19!). Most of these nutrients can be obtained from food, but if some are in limited supply in your child’s diet due to allergies, dietary restrictions or picky eating, you might consider supplementing.
#1: Vitamin D
Vitamin D is a key player in regulating immunity and inflammation. During the pandemic a lot of research has looked vitamin D status and the risk of catching Covid-19, as well as links to outcomes of the virus: one study found that those with vitamin D deficiency were 70% more likely to test positive for Covid-19 than those with adequate D status (2), while another found that patients hospitalized with Covid-19 were significantly more likely to be deficient in vitamin D than controls (3). Vitamin D deficiency is widespread, with approximately half the population having inadequate levels - those who are obese, have darker skin tones, and the elderly are at even greater risk (these groups are also hardest hit by Covid-19).
Children tend to have higher levels of vitamin D (perhaps because they spend more time in the sun), but 10% of children are still estimated to be deficient (<15 ng/ml), and these rates are even higher among kids in the aforementioned high risk categories. On top of this, a further 60% of children may have suboptimal levels (≤20 ng/ml; 4), putting them at risk for deficiency. Older infants and toddlers who are breastfed may also be at higher risk of deficiency due to low vitamin D levels in breastmilk (this can be rectified with maternal supplementation). Your pediatrician can test for vitamin D levels; some experts at Hopkins believe this should be routine for at-risk groups (5).
All children aged 1-18 years old need at least 600 IU (15 mcg) per day to maintain adequate levels; the Endocrine Society suggests that up to 1000 IU (25 mcg) may actually be needed for certain subgroups. As you probably know, the main source of vitamin D is the sun - our skin makes it when exposed to sunlight. Ten to fifteen minutes of sun on the arms and legs a few times per week is typically adequate for light-skinned individuals to get enough vitamin D, but those with darker skin tones may need double the exposure. Also, if you live in the Northern states, there’s not enough sun outside of the summer months to synthesize vitamin D (and if you routinely apply sunscreen to your child in the summer, it’s going to be limited then too).
As for food sources, oily fish is the best source of vitamin D3 (3 oz of salmon = 570 IU), and a little bit can be found in egg yolks (I large egg = 45 IU) and cheese (1 oz cheddar = 12 IU). Plant sources like mushrooms contain D2, an inferior form that the body has to convert (1/4 cup white mushrooms = 180 IU). Most milks in the US have added vitamin D (1 cup = 100-140 IU), which is where most kids are going to be getting it from, but check that it’s D3, not D2. Also know that vitamin D needs fat to be absorbed, which means that whole milk is going to be a better source for your child than fat-free milk.
Vitamin D is one nutrient that should probably be supplemented for most kids due to low availability from food and limited exposure to sun as we head into fall and winter. Look for a supplement that contains D3, in an oil (drops like this from Carlson Labs are good for kids); give 400-800 IU per day for maintaining levels (more if the child is deficient).
Zinc is a mineral and an immunity all-star; low zinc status puts us at greater risk for various infectious diseases. A recent study found a significant link between patients’ zinc levels on admission to hospital with Covid-19 and disease outcomes, concluding that low zinc was a risk factor for greater severity and higher mortality (6). Zinc deficiency can present as a loss of sense of smell and taste, which is also recognized as a symptom of Covid-19 infection. This makes physiological sense: when we catch a virus our zinc levels drop in the acute phase, as the body uses it to fight the infection (7). Preventive zinc supplementation has been shown to reduce the incidence of infectious diseases like pneumonia and diarrhea in children in developing countries (8), and maintaining adequate levels of zinc is important for optimal immune function.
Your child needs different amounts depending on their age group:
Most kids in the US get adequate zinc from food. The best sources are protein foods like meat and seafood, nuts, beans, and dairy products, which the majority of US children eat plenty of. Good animal-based sources are beef (3 oz = 7 mg), crab (3 oz, cooked = 6.5 mg), and chicken (3 oz, dark meat = 2.5 mg). Dairy sources include Swiss cheese (1 oz = 1.2 mg), milk (1 cup = 1 mg) and yogurt (1/2 cup = 0.8 mg). Top plant-based options are baked beans (1/2 cup = 3 mg), pumpkin seeds (1 oz = 2.2 mg), cashews (1 oz = 1.6 mg) and oatmeal (1/2 cup = 1 mg).
If you have a particularly picky eater, or a vegetarian or vegan child, you may want to consider a supplement. Look for something that offers at least half of the recommended daily allowance for your child’s age group (above). I don’t recommend supplementing with more than the RDA or for extended periods - this can upset the balance of other minerals like iron and copper.
#3: Vitamin C
Vitamin C is a water-soluble vitamin and a powerful antioxidant; it is important to get enough for healthy immune function. There is some evidence (9) that it may reduce the severity of colds and other upper respiratory infections slightly when taken preventively (it doesn’t seem to stop people from getting colds, but they’re less serious when they do). However, there isn't strong evidence supporting ongoing preventive supplementation with vitamin C, and it hasn’t really lived up to it’s promise against Covid-19 (10).
How much your child needs depends on their age group:
These are the minimums needed to prevent scurvy, not necessarily the amount needed for optimal functioning, so getting more is definitely not a problem! The majority of kids in the US get adequate vitamin C from foods - fruits and vegetables are the best sources. Whole fruits are better than juice, and raw fruits and veggies have more vitamin C than cooked (because some is destroyed in the cooking process). Vitamin C can be found in oranges (1 medium = 70 mg), kiwi (1 medium = 64 mg) and strawberries (1/2 cup = 49 mg), plus vegetables like bell peppers (1/4 cup = 47 mg), broccoli (1/4 cup = 25 mg), Brussels sprouts (1/4 cup = 25 mg) and cauliflower (1/4 cup = 13 mg).
Looking at these numbers you can see that most kids will be meeting the minimums, but picky eaters who don’t get enough fresh produce each day might be at risk for vitamin C deficiency (and other vitamins and minerals too). Supplements may be helpful while working on improving dietary diversity; you can safely go from the RDA up to 250 mg. Vitamin C is water soluble so supplementing is low risk - the worst-case scenario is looser stools if an excess is consumed.
These fatty acids are essential and have a regulatory effect on the immune system, bringing it back into balance: most of the fats in the Western diet are inflammatory (omega-6s), while the omega-3s are anti-inflammatory. Both are important, but most people are getting way too much of the former and not enough of the latter. Omega-3s up-regulate the activity of neutrophils (our first line of defense against pathogens), help activate T cells, and can modulate cytokine responses (11). Whether or not they’re useful in the fight against respiratory diseases is unclear, but they’re important for general health and have few downsides.
The omega-3 fatty acids (EPA and DHA) can only be found in oily fish (e.g. salmon, mackerel, rainbow trout, sardines and tuna), while their less-potent precursors (ALA) are found in nuts and seeds (e.g. flax, chia, walnuts). Most children get adequate ALA but very little DHA, because most kids aren’t eating fish on a regular basis! If this is true for your child, consider a high-quality supplement with at least 200-300 mg of DHA/EPA per serving from low mercury fish. Nordic Naturals are a reliable brand with all different options for kids including liquids, gummies and chewable soft gels.
These friendly microbes also play a role in our immune health, and may reduce the risk of respiratory diseases (12). Particular strains of interest include Lactobacillus species L. planetarium, L. paracasei and L. reuteri. Research in this area is ongoing, but there are general health benefits and no known drawbacks to getting more good bacteria into our kids’ lives, especially in the fight against pathogenic microbes.
Common food sources are yogurt, kefir, pickles (truly pickled, not in brine or vinegar), kombucha and kimchi. If your child doesn’t enjoy many of these foods, consider a probiotic supplement with a few different strains, especially if they have a history of antibiotic use.
Last but not least: SLEEP!
Kids need to be getting adequate sleep in order for their immune systems to function optimally (we all do). As they get back into the school routine, make sure they’re getting enough for their age group:
To wrap up: offer your child plenty of fresh fruits and vegetables, a variety of protein foods (animal- and plant-based) and include fish a couple of times per week. If they drink milk, make sure it’s fortified with D3 and not fat-free. If you need to plug some dietary gaps, supplements can help. Round off with a healthy dose of sunshine, fresh air, and plenty of rest. Here’s to a healthy and happy school year!
Hi, I'm Amy. I'm a nutritionist in the DC area, working with clients of all ages, focusing on prenatal and pediatrics. I'm all about straightforward, evidence-based health & wellness advice - because life/parenting in the modern world is complicated enough!