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  • Dr. Kate Henry

Nutrients & Lifestyle Factors for Optimal Immune Function

Updated: Mar 15, 2022

*I published this back in March, 2020. It's still true. Now there's even more evidence to support these claims, which you can check out on PubMed by clicking the links under each nutrient.*

Your immune system is naturally and powerfully anti-viral when you give it the right ingredients.

We all think about amping up our immunity when a new cold, flu or virus is going around. With coronavirus making the news, its natural to wonder what you can do to keep yourself from getting sick.

Luckily, there are a few proven, strategic ways to supercharge your immune system. Scroll down learn more about why these strategies work.

  • Vitamins A, C & D

  • Zinc

  • Probiotics

  • Herbal medicines & medicinal foods like olive leaf, elderberry, etc.

  • Sleep

  • Hygiene

  • Nature

  • Movement

Vitamin D: Optimize your levels

Vitamin D plays an important role in regulating the immune system. If you have low levels of vitamin D, you're more likely to get sick and get a more severe form of viral and bacterial infectious illnesses than someone who's not deficient.

Check out the COVID-19 specific research on the role of vitamin D in reducing mortality from this particular viral illness. It's compelling. Your takeaway should be that you don't want to have a vitamin D deficiency when you're exposed to SARS-CoV-2.

How do you know if you're deficient?

Ask your doctor to check your levels or order a test on your own. 92% of US adults do not consume enough vitamin D through diet, according to the CDC. So it's quite common to be deficient.

How do you get more vitamin D?

Natural sources of vitamin D include sunlight and foods like cod liver oil. This link leads to a table of the top sources of Vitamin D compiled by the NIH. If you haven't been consuming much of these foods, especially after a long winter, it's a good idea to check your levels make sure you're not deficient and then determine along with me or your doctor how much to supplement.

2000 IUs of vitamin D per day was shown to prevent influenza and rotavirus infections in several randomized controlled trials. You may need more or less depending on your individual health, particularly if you've got kidney issues. This isn't something you want to guess about. Feel free to schedule a free Discovery Call with me if you want to learn more about vitamin D and your individual health and goals.

Vitamin A

Vitamin A is a building block for both innate and adaptive immunity. It helps to create healthy mucosal membranes in your respiratory and gastrointestinal tract, and aids in the production of immune cells. Most doctors don't check for vitamin A levels because an overt deficiency is uncommon in the U.S., but your levels can absolutely be suboptimal due to a diet low in fruits and veggies. (PMID: 11375434)

Consider including more food sources of vitamin A like sweet potatoes, beef liver, carrots and spinach in your meals throughout the week. If you're not able to make these diet changes or think you might need more help, chat with a health professional about how to supplement vitamin A safely. It needs to be done with a doctor and carefully, particularly if you are a woman of reproductive age.

Stay tuned for a post on growing your own garden so that you can keep your immune system optimal all year long. The shortages of food that we're seeing as a result of this virus may happen again. With a small garden, you can be well-stocked with vitamin A-rich veggies no matter what.

Vitamin C

Vitamin C, like vitamin A, helps with the innate and adaptive arms of the immune system. It also helps white blood cells kill pathogens that could otherwise cause illness.

You can take a low dose of vitamin C daily to keep your immune system ready for battle throughout cold and flu season. Many people take 500mg of vitamin C on a full stomach comfortably without side effects a couple of times per day as part of a health maintenance routine. You'll know you're taking too much if you get loose stools. Start low and increase slowly. If you're allergic to citrus or corn, make sure to read the source of vitamin C on the label of a supplement before taking it.

Consuming a diet high in red and orange fruits and veggies is a natural way to get more vitamin C. Start by adding red peppers to soups, and munching on citrus fruits and broccoli when you can. As a bonus, vitamin C also increases the absorption of other important minerals like iron when taken with food.


Zinc is kind of an unsung hero of the human body. It's responsible for catalyzing over 100 enzymatic reactions in the body that regulate DNA synthesis, immune function, wound healing and growth.

Zinc deficiencies can result from conditions like gastrointestinal disorders, excessive alcohol intake, and diets low in protein, and they're not uncommon in the U.S. population. Low zinc levels can lead to more frequent infections, so it's important to think about when you're trying to optimize your immune system. Luckily, a simple blood test can tell you if you're deficient or not.

If you want to increase your intake of zinc naturally, consume things like oysters, crab, beef, beans and nuts in abundance. You can also find zinc lozenges in your local health food store, which you should always take on a full stomach to avoid nausea. Not everyone needs zinc and too much can cause side effects, so work with a health care provider to find the ideal dose for you.

Herbal Medicines & Medicinal Foods

Olives and berries are medicinal foods that naturally boost immunity because they contain key vitamins, minerals, polyphenols and micronutrients that your immune system needs to function at its best.

They're also easy to include in your diet. You can put berry syrup on top of waffles, oatmeal or pancakes in the morning in place of syrup, or in tea in place of honey. You can consume olives as a healthy snack with gluten-free crackers, or add organic olive oil to salads and other cooked dishes.

While other herbs like echinacea and even mushrooms can be helpful, you should talk with your doctor before taking them, since they are stronger medicines and can have side effects depending on your personal heath history. Schedule a botanical medicine consult to see if more powerful herbs could be right for you right now. Make sure to source your herbs locally if you can, and always buy organic to avoid consuming chemicals and pesticides with your herbal medicines. If you're local to Chester County, places like the Prana House, Lionville Natural Pharmacy, and Kimberton Whole Foods are good places to shop for herbal medicine.


There's lots of evidence that probiotics reduce the risk of catching colds and winter / spring viruses. Pick a pharmaceutical grade supplement with lots of lactobacillus to start. While yogurt and other food sources of probiotics are good, consuming them in your diet is is generally not going to be enough if you're trying to change your flora quickly. Your local health food store should stock at least one probiotic blend that has a few billion strains. Your local health care practitioner and I have good recommendations if you need one.

Sleep: 8 hours

Sleep is when your body does most of its cleanup, healing and repair. You need to be well rested in order for your immune system to function at 100%. People who sleep less than 8 hours per night are at increased risk of infection and inflammatory illnesses. (27510422)

If you aren't a good sleeper, there are easy things you can try to enhance the quality of your slumber that are safe, effective and cheap. Consider a warm bath before bedtime, calming teas like chamomile and lavender, magnesium and low doses of melatonin short-term. Rule out conditions like sleep apnea or a sleep disorder if sleep has been an issue for you for a while. Schedule a consult with me if you need more help, since there are more powerful therapies available for sleep if the standard stuff doesn't work. Sleep is one of our most important foundations for a healthy life and you should get lots of it.


It's worth repeating that you should wash your hands thoroughly and regularly, but especially after coughing or sneezing into them. Don't be afraid to wear a mask around sick people, or to ask them to if you'll be within 6 feet of them for extended periods of time. Germ theory is real. We stopped debating this a really long time ago. (PMC3285078, 26986125)

Protect others and don't feel bad about insisting those around you practice good hygiene / stay away if they are sick. It's a cheap, easy and chemical free way to prevent illness.


Exercise and fresh air are good for the immune system. Don't stay inside surfing devices and social media during a pandemic. It's not good for your mind, body or spirit. Being in nature raises levels of natural killer cells in your immune system, and decreases inflammatory markers as well as stress hormones. This equates to a free boost for your immune system that has no negative side effects. Nature preserves in Chester County are still open, and so are green spaces that are shared by the community. Get outside for 30 minutes per day as a start and watch your blood pressure drop and your mood improve as a bonus. (PMC6886167)


Wondering how much exercise you need to do for your immune system to benefit? Going out for a walk with your dog, playing with your kids, or dancing for an hour each day are perfect examples of the type of *light*, *regular* exercise that boosts your immune function (PMC6523821).

On the flip side, both excessive exercise and lack of exercise decrease immunity. The key here is moderation, movement and consistency. Don't sit all day or work out until the point of exhaustion if you plan to not get sick.

If you're not sure how to incorporate medicinal movement into your routine, contact my trusted colleagues at Kinetic Physical Therapy or sign up for a the 21 Day Restart program to get a custom movement plan designed for you, your body, your lifestyle and your goals.

Functional & Naturopathic Medicine

As a doctor with advanced training in nutrition, botanical medicine, and exercise therapy, I regularly help clients optimize the key vitamins and minerals that impact their immune function as part of their whole-person health plans. Head on over to the website to learn more about what I do and to schedule with me.

As always, this article contains helpful info, but no medical advice, so talk to me or your doctor before altering your health routine as a result of what you read.

Warmth & wellness,

Dr. Kate


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