By Beth Ellen DiLuglio, MS, RDN, LDN
It is well known and widely accepted that what we choose to eat has a profound and lasting impact on our health. This universal truth is especially relevant in times of immune challenge.
The human body relies on a variety of nutrients, including macronutrients, micronutrients, and phytonutrients. They must come from the diet and without these vital factors, dysfunction will occur.
An abundance of research recognizes the critical role that nutrition plays in immunity. “Many foods or food-derived materials improve or enhance immune functions in a wide range of human subjects; and foods with immune-modulating activities affect either innate or acquired [adaptive] immunity.”
Nutrients specifically relevant to immune function include vitamins A, folate, B2, B6, B12, C, D, and E; zinc; copper, magnesium, iron, and selenium.   “Practically all forms of immunity may be affected by deficiencies in one or more of these nutrients.”
Researchers recognize and confirm that: 
“Micronutrient deficiencies are a recognized global public health issue, and
Poor nutritional status predisposes to certain infections.
Immune function may be improved by restoring deficient micronutrients to recommended levels,
Thereby increasing resistance to infection and supporting faster recovery when infected.
Diet alone may be insufficient and tailored micronutrient supplementation based on specific age-related needs necessary.”
We must pay especially close attention to vitamin D status because dietary sources are limited, and suboptimal levels are common. A deeper dive into vitamin D and immunity reveals that B and T immune cells and antigen-presenting cells synthesize the active form of vitamin D which in turn is capable of modulating both innate and adaptive immunity. Insufficiency of vitamin D is associated with increased susceptibility to infection as well as increased risk of autoimmunity. 
Another dietary nutrient of particular importance to humans is vitamin C. The vast majority of mammals produce their own vitamin C at a rate of ~50 mg/kg/day. However, humans and some mammals such as primates are unable to do so. Those wily wildbeasts consume ~20-106 mg/kg/day while humans consume a paltry ~ 1mg/kg/day. If we do the math for a 150 pound/68 kg person, they may need ~3400 mg of vitamin C on a good day and more in the face of stress and infection. However, individuals with oxalate-based kidney stones, hemochromatosis, or G6PD disease must limit their intake of vitamin C.
Of course, essential nutrients exist in a complex matrix that we call food. Plant-based foods and compounds are unique sources of countless “phytonutrients” or “phytochemicals,” many of which “exhibit anti-inflammatory, antimicrobial, and angiogenic activity.”
Fresh, whole foods in general are a cornucopia of immune-supportive nutrients that are absent from highly processed foods. A diet that relies primarily on processed foods will directly compromise immunity, jeopardize, cardiometabolic health, and contribute to chronic disease. The choice is ours.
Chicken soup (esp. fed omega-3s)
Citrus (no grapefruit if on meds)
Dark chocolate, 60% cocoa
Dark leafy greens
Fish (cold water, oily)
Peppers, jalapeno, bell, chili
Protein sources, high quality, meat, omega-3 eggs, oysters
Seeds, pumpkin, sunflower
Whey protein (found in cow’s milk, powder supplements, high in cysteine)
#1 = Well-balanced multivitamin mineral supplement Alpha lipoic acid Arginine (if no sepsis) Beta-glucan Curcumin Elderberry Glutamine (if no liver or kidney compromise) Nucleotides Organic greens powder/supplement Probiotics Turmeric, curcumin Whey protein powder
Food sources of nutrients Linus Pauling Institute Micronutrient Information Center at OSU
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Used with permission, Dr. Dicken Weatherby OptimalDX.com