On a daily basis, we are constantly exposed to potentially harmful microbes of all sorts. Our immune system, a network of intricate stages and pathways in the body, protects us against these harmful microbes as well as certain diseases. It recognizes foreign invaders like bacteria, viruses, and parasites and takes immediate action. Humans possess two types of immunity: innate immunity (protective barriers such as our skin, mucus, stomach acid, enzymes, and immune system cells) and adaptive or acquired immunity (a system that learns to recognize and attack a pathogen that enters our body). However, a range of factors can depress the immune system, such as environmental toxins (e.g. smoke and other particles contributing to air pollution), certain diseases (e.g. autoimmune and immunodeficiency disorders), excess weight, chronic stress, lack of sleep, and poor diet.
Eating enough nutrients as part of a varied diet is required for the health and function of all cells, including immune cells. Certain dietary patterns may better prepare the body for microbial attacks and excess inflammation, but it is unlikely that individual foods offer special protection. Each stage of the body’s immune response relies on the presence of many micronutrients. Examples of nutrients that have been identified as critical for the growth and function of immune cells include vitamin C, vitamin D, zinc, selenium, iron, and protein (including the amino acid glutamine). They are found in a variety of plant and animal foods. Diets that are limited in variety and lower in essential nutrients, such as vitamins and minerals, can negatively affect a healthy immune system. There is growing evidence that a Western diet high in refined sugar and red meat and low in fruits and vegetables can promote disturbances in healthy intestinal microorganisms, resulting in chronic inflammation of the gut, and associated suppressed immunity.
The microbiome is an internal metropolis of trillions of microorganisms or microbes that live in our bodies, mostly in the intestines. It is an area of intense and active research, as scientists are finding that the microbiome plays a key role in immune function. The gut is a major site of immune activity and the production of antimicrobial proteins. Our diets play a large role in determining what kinds of microbes live in our intestines. A high fiber plant-rich diet with plenty of fruits, vegetables, legumes, and whole grains appears to support the growth and maintenance of beneficial microbes. Certain helpful microbes break down fibers into short chain fatty acids, which have been shown to stimulate immune cell activity. These fibers are sometimes called prebiotics because they feed microbes. Therefore, a diet containing probiotic and prebiotic foods may be beneficial. Probiotic foods contain live helpful bacteria, and prebiotic foods contain fiber and oligosaccharides that feed and maintain healthy colonies of those bacteria.
We have known for a long time that nutrition is intricately linked to immunity and to the risk and severity of infections. Poorly nourished individuals are at a greater risk of various bacterial, viral, and other infections. Conversely, chronic or severe infections lead to nutritional disorders or worsen the nutritional status of affected people. Therefore, it is imperative for all of us to pay attention to our diet and nutritional status during the ongoing COVID-19 pandemic.
A deficiency of just a single nutrient can alter the body’s immune response. Animal studies have found that deficiencies in zinc, selenium, iron, copper, folic acid, and vitamins A, B6, C, D, and E can alter immune responses. These nutrients help the immune system in several ways: working as an antioxidant to protect healthy cells, supporting growth and activity of immune cells, and producing antibodies. Epidemiological studies find that those who are poorly nourished are at greater risk of bacterial, viral, and other infections. Eating a good quality diet can prevent deficiencies in these nutrients.
The elderly are a particularly high-risk group. The immune response generally declines with increasing age as the number and quality of immune cells decreases. This causes a higher risk of poorer outcomes if the elderly develop chronic or acute diseases. In addition, about one-third of elderly individuals in industrialized countries have nutrient deficiencies.
To help support a healthy immune system eat a healthy and balanced diet.
Karimi, H.
Master of clinical Nutrition & Dietetics
Reference
-Healthy Living Guide 2020/2021.A Digest on Healthy Eating and Healthy Living. Department of Nutrition at The Harvard.
