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Nutrition is a critical determinant of immune responses and malnutrition is the most common cause of immunodeficiency worldwide. Your body requires both macronutrients and micronutrients to do its job of keeping you safe from invading pathogens. Deficiency in protein, and micronutrients zinc, selenium, iron, copper, vitamins A, C, D, E, and B-6, and folate, even mild deficiency, is associated with immune dysfunction and increased infection complications.
How Your Immune System Works
Your immune system is complex and its response is affected by the pathogen form, the route of infection, and your health status before infection. There are multiples types of cells that defend your body, and different ways in which they work. Your white blood cells account for 1% of your blood, but are your greatest defense against invading pathogens.
White blood cells are divided into two groups; Granulocytes and Agranulocytes. Granulocytes originate in the bone marrow and include Neutrophils, Eosinophils and Basophils. Agranulocyte Monocytes original in the bone marrow, while agronulocyte Lymphocytes originate primarily in the thymus.
We are exposed to a variety of viruses throughout our lives. How your body responses to these viruses is dependent on the virus itself, it's mechanisms of action, and your underlying health. Depending on the path of infection, your body offers multiple ways to defend you against viral pathogens.
The humoral immune response is named for the immune cells found in the humor of the body (the body fluids, or plasma). These refer to the reactions of the B- and T-cell lymphocytes. Antibodies are produced by the B-cells (with the help of T-cells) which identify and destroy the invading pathogen and prevents the spread of disease. Antibodies block virus-host cell interactions and label viral antigens on virus-infected cells which increases killer cell activity.
Cell mediated immunity refers to the immune responses that do not require antibodies. This is the recognition of virus infected cells by leukocytes (Eosinophils and Monocytes), and the increased phagocytosis and secretion of cytokines that signal natural killer cell activity.
Protein Malnutrition & Immune Function
Protein is a macronutrient, and is essential for your body to function. Dietary proteins are constructed of amino acids. During digestion, these amino acids are separated and absorbed, and are responsible for the majority of cellular work. Amino acids work as flags on the outsides of cells to signal that the cell is damaged or infected. Cell culture studies show that branch chain amino acids are absolutely essential for lymphocytes to function. T-cells in particular are highly dependent on amino acids, such as arginine.
It is well accepted in research that protein malnutrition reduces the ability of the immune system to function properly. In those with protein malnutrition negative changes to the immune system are seen. There is a reduction in the size and weight of the thymus (remember, it produces a large amount of your immune cells), delayed response to new and recall pathogens, reduces maturity of T-cells, reduction in lymphocyte protein receptors that identify pathogens, decreased antibody production, decreased cytokine production, and decreased phagocytosis...pretty much a complete decrease in immune response and function. These changes are seen in moderate deficiencies.
Supplementation with specific amino acids has been shown to enhance or preserve immune function in high risk patient, as well as improve the capacity to resist infection. Supplementation and dietary changes may take weeks to months to improve immune responses. Arginine supplementation has been used to normalize T-cell production with great success.
Micronutrients & Immune Function
Contrary to what most of you have been taught, the US population is riddled with nutritional deficiencies that could inhibit proper immune function.
Trace minerals and vitamins play critical roles in the immune system pathways. Many are enzyme cofactors, or are required for processes to occur properly. It is rare to have a single nutrient deficiency. More often than not, those with nutritional deficiency have multiple nutrients missing from the diet. Changes in the immune system begin to occur in the early stages of deficiency, and may occur before serum testing can detect deficiencies.
Zinc is a trace mineral that is crucial for normal development and function of immune cells, proper phagocytosis, and prevents free radical damage as an antioxidant. Zinc is a cofactor for many of the enzymatic functions used in immune responses. In human model studies of zinc restriction, blood levels of zinc remained the same while immune cell zinc concentrations decreased, making plasma zinc testing inaccurate for diagnosing mild deficiencies that could affect immune function. A deficiency in Zinc is associated with an increased risk of pneumonia and respiratory infections.
Selenium is important for initiating immunity, and is also involved in regulating excessive immune responses and chronic inflammation. Selenium bound proteins are responsible for immune cell communication. A deficiency in selenium in those hospitalized with respiratory illness was correlated with poorer prognosis. Supplementing with additional selenium when not deficient can cause negative impacts on the immune system, so high dose supplementing is never recommended. Dietary intake increases are your best way increasing total selenium.
Iron is necessary for your immune cells to multiple and mature, specifically lymphocytes, as well as the expression of cytokines. Bacterial infections can be negatively impacted when excess iron is consumed as it is used by bacterial cells to increase their ability to multiple.
The immune system requires copper to function, but the exact mechanisms of action are still unknown. Neutrophil production is often used as a measure of copper deficiency. Not only is the total count of neutrophils reduced in the presence of copper deficiency, but their ability of phagocytosis is affected as well.
Vitamin A (retinol) is a fat soluble vitamin involved in the development of the immune system and plays regulatory roles in cellular immune responses and bone marrow homeostasis. Vitamin A deficiency leads to a defect in T cell-mediated and antibody-dependent immune responses. Vitamin A deficiency in America is very common, with more than half of the population deficient in dietary Vitamin A.
Vitamin C is an essential antioxidant and cofactor for enzymes. Vitamin C enhances microbial defense, and has been shown to enhance differentiation and proliferation of lymphocytes. Vitamin C deficiency results in impaired immunity and higher susceptibility to infections.
Vitamin D is produced by the body and consumed in the diet. Receptors for Vitamin D have been found throughout the body, and on lymphocytes. Vitamin D is capable of inhibiting pulmonary inflammatory responses while enhancing defense mechanisms against respiratory pathogens. A deficiency in vitamin D is associated with increased susceptibility to upper respiratory tract infections and a decrease in forced air volume. Over 90% of Americans are not getting enough Vitamin D. A simple blood test could help you determine the right supplemental dose of Vitamin D for you.
Vitamin E is a well known fat soluble antioxidant. Vitamin E plays an important role in the differentiation of immature T cells in the thymus. Vitamin E deficiency is extremely common in the US, and with advanced age, with over 90% of the US population not consuming adequate dietary Vitamin E. Respiratory illnesses affect elderly more aggressively, and vitamin E deficiency is more common as you age. Vitamin E supplementation has been shown to improve immune responses in the elderly.
Vitamin B6, pyridoxine, is requires for the formation of white blood cells. It also helps produce a protein that signals immune cell actions. Lymphocyte differentiation and maturation are altered by deficiency, immune responses are reduced, and antibody production may be indirectly impaired.
Folate is another B vitamin that is required for a healthy immune system. Folate is required for DNA and protein synthesis, so every cell is affected by folate deficiency. Deficiency is associated with decreased thymus function and lower response of T-cells. Studies show a correlation with decreased serum folate levels and increased homocysteine in pneumonia cases among elderly. Supplementation with folate may reduce the risk of pneumonia in respiratory illness.
Increasing Your Immune Health with a Nutrient Dense Diet
Nutrition interventions, aka changing your diet and including nutrient dense foods in addition to supplementation, has been shown to be beneficial in the prevention of infectious disease. In America, we are not immune to nutritional deficiencies. The standard American diet is riddled with nutritional deficits. Not all calories are created equal. Your body needs micronutrients, and often the American caloric intake is devoid of micronutrients.
If you want your body function optimally, you need to give it nutrient dense food. This is your best defense against viral infections, cancers, and other degenerative diseases such as Type 2 diabetes and hypertension.
Start by increasing your intake of fruits and vegetables. The standard American diet has left over 80% of you deficient in your fruit and vegetable intake. Your diet should be primarily based on vegetables, fruits, nuts and seeds, legumes, whole grains, and quality fats and proteins. What does this look like?
You may also need to incorporated nutritional supplements. If you are starting off deficient, consuming enough nutrient dense food to correct that deficiency may not be possible without nutritional supplement support.
For a complete list of foods rich in these immune boosting vitamins and minerals, shoot me an email.