Dietitians and research scientists share the long-held belief that nutrition can exert a powerful influence on one’s overall health. Poor dietary habits rank as the second-leading risk factor for both mortality and disability-adjusted life-years (DALYs) worldwide. The amount and type of nutrients consumed show a direct correlation to the body’s immune health; inappropriate nutrient consumption leading to the development of many diseases reflects an improperly functioning immune system. Read on to learn the mechanisms of this relatedness, as well as how the dynamics shift throughout one’s lifespan.
A New Concept Emerges
Nutritional immunology has emerged as a newly recognized category of clinical and public health importance. As early as 1810, scientists recognized a connection between lymphoid tissue atrophy and malnutrition. Discovery of vitamins in the early 1900s led to knowledge of their contribution to immunity. New concepts of investigative research in both fields – nutrition and immunology – helped propel the movement forward.
Through clinical studies, epidemiology and various types of behavioral studies, experts have witnessed an increasing appreciation for the role that diet plays in controlling immunity, health and disease across the human lifespan. It seems as if diet may serve as a major modifiable target for interventions designed to improve a body’s immunological responses to various pathogens.
A Brief Overview of the Immune System, From Infancy Through Old Age
The human body houses both innate and adaptive cells within its immune system. The common condition of inflammation, as associated with injury and malaise, comprises a large portion of the innate system; nutrition can have a significant effect on immunity and, hence, on the development of a diseased state.
The process of nutrition influencing immunity begins in utero, since the maternal diet from the point of conception up until birth serves as the sole influence programming an infant’s immune system. New mothers who choose to nurse their newborns provide nutrition as well as passing along aspects of their own innate immunity. Once a child moves past a diet consisting solely of breast milk, other early dietary factors – such as exposure to preservatives, polyunsaturated fatty acids, and perhaps a lack of consumption of key micronutrients/vitamins – will begin the formation of his adaptive immune cells.
Throughout adulthood, a longtime frame exists during which chronic exposure to poor nutrition, heavy metals/additives, and gut dysbiosis may predispose bodies towards elevated inflammation and immune dysfunction. Many lifestyle choices work together over these decades, and the effects add up.
Finally, as we enter our senior years and activity levels/metabolisms slow, waning appetites often lead to a significant lack of key nutrients. Taken together, these pose threats to an ageing immune system, making our older population particularly susceptible to a host of maladies. We will discuss in more detail the specific micronutrients which may help delay or reverse the effects of aging on immune function and inflammation.
The Mighty Micronutrients
The role nutrition plays in supporting the immune system, well-established through a host of clinical data, hinges on key vitamins and minerals. Vitamins A, B6, B12, C, D, E, and folate (folic acid) frequently surface in research articles covering this topic. In addition, substances known as trace elements, including zinc, iron, selenium, magnesium, and copper, help support the body’s immunity. Inadequate intake, a problem prevalent among certain demographics throughout the world, leads to a decrease in resistance to infections and, subsequently, an uptick in illness due to a downgraded immune system. public health officials are encouraged to include nutritional strategies in their recommendations to improve public health.
Our nutritional choices throughout life may even determine the risk and severity of an infection. An interesting bidirectional relationship exists between the nutrients we consume and the reaction they elicit in our immune system. The macro-, micronutrients, and phytonutrients contained in certain fruits and colorful vegetables help foster robust immune responses. When an infection does present itself, these same micro-and phytonutrients provide vital antioxidants and anti-inflammatory nutrients, such as beta-carotene, vitamin C, vitamin E, and polyphenolic compounds. Sufficient intake of these when fighting an illness results in stronger immune functions.
Understanding the DII
In an effort to categorize and promote healthy foods, a system known as the dietary inflammatory index (DII) assigns a score to foods in accordance with their effects on inflammation and stress in the body. Culled from research articles published from as far back as 1950, the system formally came into use in 2004.
In addition to their anti-inflammatory properties, as mentioned above, some foods/nutrients also confer antioxidant, antiviral, and immune-enhancing properties. Dietitians and medical professionals might go so far as to recommend a diet that can help counteract or even mitigate symptoms associated with chronic pulmonary and gastrointestinal in conjunction with traditional prevention/control and treatment protocols. Based upon the DII system, an anti-inflammatory diet recommends turmeric, ginger, garlic, onions, saffron, dietary vitamin C, vitamin D, zinc, and omega-3. All of these, individually and more so together, have demonstrated the capacity to reduce infection symptoms and their duration.
Obesity falls under the broad category of conditions that can have a profound effect on one’s health/morbidity. Studies have suggested that obesity may relate to inflammation; regardless of whether one causes the other, both may benefit greatly from assuming a DII meal plan. A review published in Archives of Endocrinology and Metabolism in 2023revealed that “use of the DII may be useful for understanding the relationship between diet and the inflammatory process related to obesity.”
Aging and the Immune System
In order to sustain life and continue developing its environs, health and well-being throughout our entire lives remains vital. Nutrition lies at the heart of the World Health Organization (WHO) Sustainable Development Goals, including bringing an end to all forms of malnutrition by 2030. While much has improved in nutritional interventions and measures related to food insecurities, we still lack research on how nutritional interventions can impact healthy aging.
The WHO views “healthy aging” as a life-long endeavor. Aging well includes components of physical, mental, social, and emotional wellbeing—all of which can have an effect on (or suffer the consequences of) dietary intake and nutritional status.
Healthy nutrition lays the framework for supporting physical growth and mental development in infants, young children, and adolescents. As we progress into young adulthood and midlife, nutritional patterns influence the development of muscle, thereby supporting key aspects of health and physical function. As we age, we expect to observe some physical/cognitive, illness-related decline; however, individuals with healthier growth at the beginning of life build biological reserves that can prevent or delay age-related problems later in life. This includes a lifetime of good nutrition, which in addition to disease prevention may facilitate the restoring of health following injury or surgery.
The Real Cost of Malnutrition
As we have come to realize, a direct relationship exists between good nutrition and a well-functioning immune system. In fact, hospitalized patients with diagnoses of malnutrition incur up to two-fold greater hospital costs for care compared to inpatient stays for adequately nourished patients. By implementing nutritional care programs for hospitalized adults, they can expect to see a substantial healthcare savings approaching $4,000. Improved nutrition care, by virtue of shoring up a patient’s immune response, has likewise aligned with fewer complications and an overall faster recovery (including a shortened hospital stay and lower readmission rates).
Nutrition and Biochemistry
Each and every cell in the human body requires energy from food in order to function, including cells of the immune system. To produce and support immune cells, the body needs the fuel provided by nutrition. In addition to fueling immune cells, various macronutrients and micronutrients offer support on many other levels:
- Work as antioxidants
- Produce antibodies
- Provide structure for immune cells
- Promote growth and activity of immune cells
- Produce white blood cells
- Regulate immune cells responses
- Lower oxidative stress and reduce inflammation
- Synthesis of immune cell DNA and protein
- Repair damaged cells and tissue
Nutritional deficiencies show direct association with impaired cell-mediated immunity. This encompasses a reduced number of circulating T-lymphocytes, particularly CD4+ helper T-cells and CD3+ CD25+ T-cells that contain the interleukin (IL)-2 receptor; decreased lymphocyte stimulation response to antigens; altered production of cytokines; decreased antibody affinity; and phagocyte dysfunction.
Diets that are limited in variety and deficient in valuable nutrients, such as those consisting primarily of highly processed foods and lacking in fresh fruits and vegetables, legumes and grains, can negatively affect a healthy immune system. Sadly, for all of this nation’s wealth, a typical Western diet remains high in refined sugar and red meat, fostering problems in otherwise healthy intestinal microorganisms. The resulting chronic gut inflammation goes hand-in-hand with suppressed immunity.
Disturbances in the Microbiome
Nutrition intake will naturally affect the gut microbiota. In turn, the gut microbiota shapes and controls the immune and inflammatory responses. As we age, changes occur in the gut microbiota; aberrations in immune competence, low-grade inflammation, and gut dysfunction most likely originate with age-related changes in nutrition. A number of the aforementioned micronutrients (vitamins C, D, and E and zinc and selenium) play roles in supporting the function of many immune cell types. Some trials have indicated that providing these micronutrients in supplementation form can actually reverse some of the immune deficits typically observed in older people and/or those whose diets reflected insufficiencies. Probiotic, prebiotic, or symbiotic strategies that modulate the gut microbiota, especially those that strive to introduce colonization of lactobacilli and bifidobacteria, have proven pivotal in shoring up inflammatory biomarkers in older people. In some cases, these same bacteria have brought about a reduction in the risk and severity of gastrointestinal infections.
Inflammatory bowel syndrome (IBS), Crohn’s disease (CD) and ulcerative colitis (UC) represent the most common of the chronic immune-mediated disorders that plague so many individuals all over the world. More than 1.5 million Americans suffer with these gastrointestinal conditions, as well as over 2.2 million Europeans. These diseases, characterized by a relapsing-remitting episodes, often require aggressive medical treatment.
Nutritional intervention plays a vital role in the daily lives of patients with IBS. Data from studies in the field of Oncology show that eating/avoiding certain foods can increase or decrease the risk for developing colorectal and other digestive cancers; this most likely relates to the pro-inflammatory aspects of certain foods. This would lead us to believe that nutrition may also affect both the pathogenesis and the disease progression of IBS.
Determining the Necessity/Benefit of Supplementation
We have identified, and extolled the virtues of, several key vitamins and trace minerals that play a central role in optimal nutrition for a healthy immune system. Going a step further, these same players serve vital roles in enhancing the world of medicine.
Oncologists often include vitamin A as an adjunct therapy in the treatment of acute promyelocytic leukemia. Vitamin C serves as a powerful weapon in a body’s fight to defeat tumor cells. Vitamin D can stimulate apoptosis (cell death), thereby suppressing the proliferation of cancer cells and delaying tumor development. The trace mineral selenium, when used as a cofactor by the immune system, can foster greater efficacy of the COVID-19 vaccine. Even cholesterol, a substance which for decades was maligned by the medical/nutrition community, appears to confer an exacting regulation of the immune function.
Supplementation with vitamins, omega 3 fatty acids, zinc and other elements offers a safe and cost-effective way to support optimal function of the immune system, with the added potential to reduce the risk and consequences of infections. Individuals should consider supplementation only when, in addition to a healthy diet, a medical professional has indicated a deficiency. While “more” may seem “better” in some instances, supplemental consumption should always fall within recommended upper safety limits set by scientific experts.
The Final Word
The possibility of enhancing the human immune system through the intake of appropriate macro- and micronutrients opens up many doors. From infancy to old age, careful attention to nutritional details can foster healthier childhood, middle adulthood, and senior functionality. This holistic approach to wellness has far-reaching potential, not only on our current health status, but on future research into prevention.
References:
https://pmc.ncbi.nlm.nih.gov/articles/PMC6212925/
https://pmc.ncbi.nlm.nih.gov/articles/PMC9772031/
https://www.mdpi.com/2072-6643/11/6/1239
https://nutritionsource.hsph.harvard.edu/nutrition-and-immunity/
https://pmc.ncbi.nlm.nih.gov/articles/PMC9526826/
https://www.tandfonline.com/doi/full/10.2147/NDS.S262364
https://www.frontiersin.org/journals/nutrition/articles/10.3389/fnut.2022.1113060/full
https://obesitymedicine.org/blog/foods-that-aid-in-stress-relief-and-lowering-inflammation/
https://pubmed.ncbi.nlm.nih.gov/34024569/
https://pubmed.ncbi.nlm.nih.gov/33092041/
https://pubmed.ncbi.nlm.nih.gov/32340216/
https://pubmed.ncbi.nlm.nih.gov/26909350/
https://nutrition.org/nutritional-immunology-across-the-lifespan/
