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Nutrition for Boosting Your Immune System

Amidst cold and flu season, it's a perfect time to boost your immune system! Nutrition is one of the primary pillars of immune system health.

Nutrition: Food is Medicine

Ditch the processed foods and focus instead on whole, real foods. Modern diets are generally deficient in vitamins and nutrients as compared to the diets of traditional peoples. Weston A. Price's studies [1] showed that the diets of traditional people contained up to ten times the amounts of vitamins and nutrients present in modern diets. Price found that the higher nutrient-content of traditional diets led to much greater immunity to infectious diseases such as then-prevalent tuberculosis.

Nutrients are best obtained through whole foods as opposed to supplements. Whole foods contain enzymes and other synergistic co-factors which best allow the nutrients to be absorbed and utilized by the body [2]. Some specific nutrients that boost the immune system are Vitamins A, C, and D. Additionally, whole raw foods such as raw milk and milk kefir have been correlated with specific immune system benefits.

Vitamin C: Fresh Fruits and Vegetables

Vitamin C is known to be an important nutrient in immune system health [3]. "Vitamin C contributes to immune defense by supporting various cellular functions of both the innate and adaptive immune system." Deficiency in Vitamin C "results in impaired immunity and higher susceptibility to infections."

Consuming plenty of Vitamin C is associated with lower incidence of illness, and higher doses of Vitamin C administered during illness have been shown to be effective at reducing the "severity of the respiratory symptoms." Vitamin C has also been shown to be effective at treating the severe symptoms associated with COVID19 [4].

Excellent food sources of Vitamin C include citrus fruits, tomatoes, strawberries, bell peppers, kiwi, mango, and snow peas.

Vitamin C easily degrades with heat [5], so food sources of Vitamin C should be consumed raw in order to gain the most benefit. Because it has been shown that high-doses of Vitamin C are needed to obtain benefit during illnesses [3], my family also has supplemental Vitamin C on-hand to use in case of illness.

Vitamins A and D: Salmon, Clams, Organ Meats and Cod Liver Oil

Vitamins A and D are especially important for immune system support [6]. Deficiency in Vitamin A is known to lead to an increase in illnesses, and it has been "well established that widespread immune alterations, anemia, and increased infectious disease morbidity and mortality occur during vitamin A deficiency [7]." Likewise, Vitamin D is known to boost the immune system [8], and "recent epidemiological evidence indicates a significant association between vitamin D deficiency and an increased incidence of several infectious diseases [9]."

When taken in supplemental form, excess Vitamin A can pose toxicity risks. However, "excess vitamin A only causes problems against a backdrop of vitamin D deficiency [10]." Thus, it is best to consume Vitamin A through foods, in the context of plenty of Vitamin D through foods and sunshine.

Organ meats, especially liver, are excellent food sources for Vitamins A and D. One easy way I have found to make sure my family is regularly eating at least a small amount of organ meats is to add finely chopped liver and heart (from the giblets) to each pot of chicken soup I make. If your family doesn't enjoy eating organ meats, dessicated liver capsules may be a good way to meet this nutrient need. Although not quite as potent as organ meats, clams and salmon are also good sources of Vitamins A and D.

Cod liver oil is a whole-food supplement that is an excellent natural source of both Vitamin A and Vitamin D. With today's widespread nutrient-deficiencies, cod liver oil can be a safeguard against frequent illnesses during cold and flu season. However, there are many inferior pseudo cod liver oils on the market. Rosita's Extra-Virgin Cod Liver Oil (EVCLO) is superior because the ancient-Viking harvesting process uses no heat, pressure, or chemicals. This minimal processing means that EVCLO is rich in naturally-occurring Vitamins A and D.

EVCLO's mild flavor and superb nutrition have made it a win-win in our household. We use both liquid and capsules of EVCLO. Weston Price found that cod liver oil worked synergistically with high-vitamin butter [1], and more recent studies have confirmed that Vitamin D works best in conjunction with Vitamin K2 [11]. Therefore, we try to make sure to take our cod liver oil at a time when we are also consuming nutrient-dense butter, egg yolks, and/or emu oil.

Immune Strength: Breastfeeding, Raw Milk and Milk Kefir

It is well known that breastfeeding is correlated with lower rates of illness and stronger immune systems. Did you know that studies have shown that raw milk has similar immune-supporting effects to breastmilk [12]?

Raw milk is a great source of immune system-boosting Vitamins A and D. Raw milk has specifically been associated with a reduced risk of respiratory infections and fever. A study of over 900 European children concluded that, "Early life consumption of raw cow's milk reduced the risk of manifest respiratory infections and fever by about 30%" [12]. Additionally, raw milk kefir has also been shown to have specific immune system boosting effects, because it stimulates and modulates the immune system [13, 14, 15].

Raw milk is one of the easiest superfoods to consume because it is delicious! Raw milk kefir tastes good, too, but it can be more of an acquired taste. In our household, kefir ranch dressing, no-cook chocolate pudding, and kefir smoothies have been the easiest ways to make sure that we're all regularly consuming kefir.

Whole Food Prescription

As Hippocrates said, "Let thy food be thy medicine and medicine be thy food." Whole, real foods nourish the immune system and make it more likely that our bodies will be able to quickly heal from illnesses, including influenza and COVID19. With healthy immune systems, we need not live in fear.


[1] Price, W. Nutrition and Physical Degeneration. Lemon Grove, CA, Price-Pottenger; 1939.

[2] David R Jacobs, Jr, Myron D Gross, and Linda C Tapsell. "Food synergy: an operational concept for understanding nutrition." The American Journal of Clinical Nutrition, Volume 89, Issue 5, May 2009, Pages 1543S–1548S.

[3]Carr, Anitra C, and Silvia Maggini. “Vitamin C and Immune Function.”Nutrients vol. 9,11 1211. 3 Nov. 2017,

[4] Mongelli, Lorena, and Golding, Bruce. "New York hospitals treating coronavirus patients with vitamin C." New York Post. March 2020.

[5] "Degradation of vitamins, probiotics and other active ingredients caused by exposure to heat, water and sunlight." Nutraceutical Business Review. August 2018.

[6] J. Rodrigo Mora, Makoto Iwata, and Ulrich H. von Andrian. "Vitamin Effects on the Immune System: Vitamins A and D Take Centre Stage", Nature Reviews Immunology. 2008 Sep; 8(9): 685–698.

[7] Semba, Richard D. Military Strategies for Sustainment of Nutrition and Immune Function in the Field. Washington DC, Institute of Medicine (US) Committee on Military Nutrition Research, National Academies Press; 1999.

[8] Vanherwegen AS, Gysemans C, Mathieu C. "Regulation of Immune Function by Vitamin D and Its Use in Diseases of Immunity", Endocrinology and Metabolism Clinics of North America. 2017 Dec;46(4):1061-1094.

[9] Kikuta J, Ishii M. "Current Topics on Vitamin D. The Effects of Vitamin D on the Immune System", Clinical Calcium. 2015 Mar;25(3):359-65.

[10] Kresser, Chris. "9 Steps to Perfect Health - Supplement Wisely"

[11] van Ballegooijen, Adriana J et al. “The Synergistic Interplay between Vitamins D and K for Bone and Cardiovascular Health: A Narrative Review.”International journal of endocrinologyvol. 2017 (2017): 7454376.

[12] Loss G, et al. PASTURE study group. "Consumption of unprocessed cow's milk protects infants from common respiratory infections." Journal of Allergy and Clinical Immunology. 2015; 135 (1): 56-62.

[13] Bourrie, Benjamin C T et al. “The Microbiota and Health Promoting Characteristics of the Fermented Beverage Kefir.” Frontiers in microbiology vol. 7 647. 4 May. 2016.

[14] Zeynep B. Guzel-Seydim, Tugba Kok-Tas, Annel K. Greene & Atif C. Seydim (2011) "Review: Functional Properties of Kefir", Critical Reviews in Food Science and Nutrition, 51:3, 261-268.

[15] de Oliveira Leite, Analy Machado et al. “Microbiological, technological and therapeutic properties of kefir: a natural probiotic beverage.” Brazilian journal of microbiology : [publication of the Brazilian Society for Microbiology] vol. 44,2 341-9. 30 Oct. 2013.

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