“The food we consume affects the strength of our immune system,” said Dr. Simin Meydani, senior scientist and leader of the nutritional immunology team at Tufts University’s Jean Mayer USDA Human Nutrition Research Center on Aging.
You won’t be able to boost your immunity by eating large amounts of one nutrient, according to Meydani. However, consuming micronutrients such as vitamin C, vitamin D, vitamin B complex, zinc and selenium can help improve the body’s defenses against colds, flu, and even Covid-19.
Instead of worrying about so-called “superfoods,” it’s important to have a large variety of foods in your diet to provide the micronutrients your body needs to create a strong cellular immune response, said Stanford School of Medicine nutrition scientist Christopher Gardner.
Gardner stated that there is not a singular food or nutrient that is most important, but rather the combination of different micronutrients working together.
Nutrition and Immunity
During the flu season or times of illness, people often seek special foods or vitamin supplements to try to boost their immunity. Some popular examples are foods with Vitamin C like citrus fruits, chicken soup, and tea with honey. However, the design of our immune system is complex and is influenced by an ideal balance of many factors, not just diet. A balanced diet consisting of a range of vitamins and minerals, combined with healthy lifestyle factors like adequate sleep and exercise and low stress, is more likely to be effective in priming the body to fight infection and disease.
What Is Our Immune System?
Innate immunity comes naturally, while adaptive immunity is acquired throughout our lifetime. We’re constantly being exposed to potentially harmful microbes every day. Our immune system, which is a network of intricate stages and pathways in the body, protects us against these harmful microbes as well as some diseases. It’s able to recognize foreign invaders such as bacteria, viruses, and parasites and takes immediate action. There are two types of immunity that humans have: innate and adaptive. Innate immunity is something we’re born with, while adaptive immunity develops over the course of our lifetime.
Innate immunity is a first-line defense from pathogens that try to enter our bodies, achieved through protective barriers. These barriers include:
- Skin that keeps out the majority of pathogens
- Mucus that traps pathogens
- Stomach acid that destroys pathogens
- Enzymes in our sweat and tears that help create antibacterial compounds
- Immune system cells that attack all foreign cells entering the body
The immune system regulates cells and organs in the body to create antibodies to foreign substances. The system adapts by remembering foreign substances so that if they enter the body again, the system is more efficient in destroying them.
Other Conditions That Trigger An Immune Response
The body views antigens as foreign and harmful substances, which prompts the immune system to take action. Allergens are a type of antigen that includes things like grass pollen, dust, food components, or pet hair. Antigens can cause an overactive response in which too many white blood cells are released. reactions to antigens vary widely from person to person. For example, someone with an allergy to mold might experience wheezing and coughing, while someone else would not have any reaction.
When the body is fighting off a foreign invader, like a virus, Inflammation is a normal and important response. Immune cells called mast cells release proteins called histamines. These histamines cause Inflammation, which can lead to pain, swelling, and fluid release. This fluid release helps to flush out the pathogens. The histamines also send signals to the body to release more white blood cells to fight the pathogen. However, if Inflammation lasts for a long time, it can damage tissue and overwhelm the immune system.
Autoimmune disorders are partly hereditary and cause hypersensitivity in which immune cells attack and destroy healthy cells.
A immunodeficiency disorder is a condition where the immune system is either not working properly, or is not there at all. There are two types of immunodeficiency disorders: those that are present at birth (congenital) and those that are acquired later in life. The most common type of immunodeficiency disorder is the acquired type, which includes diseases such as AIDS and certain types of cancer (leukemia and multiple myeloma). People with acquired immunodeficiency disorders are more likely to get sick from infections and other diseases because they do not have the normal defenses against these things.
What Factors Can Depress Our Immune System?
As we grow older, our internal organs may not function as well as they used to. This is because the organs that help us fight off infections, like the thymus or bone marrow, produce fewer immune cells. Another reason why our immune system may not work as well as it used to is because we may not have enough of the right vitamins and minerals (micronutrients).
- Environmental toxins (smoke and other particles contributing to air pollution, excessive alcohol): These substances can impair or suppress the normal activity of immune cells.
- Excess weight: Obesity is associated with low-grade chronic inflammation. Fat tissue produces adipocytokines that can promote inflammatory processes. Research is early, but obesity has also been identified as an independent risk factor for the influenza virus, possibly due to the impaired function of T-cells, a type of white blood cell.Â
- Poor diet: Malnutrition or a diet lacking in one or more nutrients can impair the production and activity of immune cells and antibodies.
- Chronic diseases: Autoimmune and immunodeficiency disorders attack and potentially disable immune cells.
- Chronic mental stress: Stress releases hormones like cortisol that suppresses inflammation (inflammation is initially needed to activate immune cells) and the action of white blood cells.
- Lack of sleep and rest: Sleep is a time of restoration for the body, during which a type of cytokine is released that fights infection; too little sleep lowers the amount of these cytokines and other immune cells.
Anti-inflammatory Foods
Eating a variety of fruits and vegetables helps to control your body’s inflammatory response to bacteria and viruses.
“A certain amount of inflammatory response is needed to get rid of the pathogens and to help the body’s immune system perform its function,” Meydani said. “But if you produce too many inflammatory components, it can be damaging to surrounding tissues. It can cause autoimmune diseases. It can cause chronic diseases.”
According to studies, chronic inflammation can cause various illnesses such as cancer, heart disease, diabetes, arthritis, depression, Alzheimer’s, and Covid-19. In extreme cases of Covid-19, an inflammatory reaction to the virus known as a “cytokine storm” can occur, leading to more severe symptoms and death.
“In relation to Covid-19, the recommendation to increase fruits and vegetable consumption is even more important,” Meydani said, “because of all the anti-inflammatory compounds such as flavonoids in them that can reduce the cytokine storm.”
A diet high in processed, fatty foods, sugary drinks, and red and processed meats can cause persistent inflammation in the body.
A diet consisting mostly of unhealthy, “ultra processed” foods like ice cream, cookies and pre-made consumer foods has been linked with a shorter life span. In two separate studies, it was found that a 10% increase in consumption of these types of foods was associated with a 14% higher risk of death from all causes.
Opt for leafy greens, tomatoes, fruits, nuts, fatty fish and olive oil to help keep your inflammatory response in check.
Research is also discovering that fermented food like kimchi, sauerkraut, and kombucha may help reduce some types of inflammation by improving the microbiome in the digestive system, as experts claim.
The Stanford research team found that the study participants who ate fermented foods had lower levels of inflammation after 10 weeks.
Does an Immune-Boosting Diet Exist?
A person needs to eat enough nutrients as part of a varied diet in order for all cells, including immune cells, to be healthy and function properly. It is possible that certain dietary patterns help prepare the body to better withstand microbial attacks and excess inflammation, but it is unlikely that any one food offers special protection. Many micronutrients are necessary at each stage of the body’s immune response. Examples of nutrients that have been identified as being critical for the growth and function of immune cells include vitamin C, vitamin D, zinc, selenium, iron, and protein (including the amino acid glutamine), all of which can be found in a variety of plant and animal foods.
A diet that consists mainly of processed foods and lack of nutrients can have a negative effect on a healthy immune system. A Western diet that is high in refined sugar, red meat, and low in fruits and vegetables can promote disturbances in healthy intestinal microorganisms, resulting in chronic inflammation of the gut and a suppressed immunity.
Are Supplements Needed?
The human body is designed to more efficiently absorb nutrients from whole fruits, vegetables, nuts, grains and proteins than from processed foods or supplements.
But people who have limited access to healthy food choices or who have certain medical conditions or anyone over the age of 65 may need to focus on adding specific micronutrients to their diet.
“I’m not talking about the frail elderly that are homebound,” Meydani said. “I’m talking about older people who are healthy, active, but above the age of 65. For them, I think certain nutrient supplementation might be very helpful.”
The Role Of Zinc
The majority of people in the United States consume enough zinc through diet alone, however a study done by Meydani’s team showed that older adults with low zinc levels in their blood were more prone to pneumonia and needed antibiotics for a longer period of time than those with higher levels.
If you take zinc lozenges in the first 24 hours of a cold or flu, it may help reduce the duration of sickness by a day, according to a review of 13 studies.
The Mineral Selenium
Selenium is a mineral found in the soil that plants absorb. It’s important for inflammation and immunity, and we need it to activate immune cells. Selenium also seems to be able to reduce inflammation.
Selenium is found in many American’s diets from food sources such as seafood, meat, poultry, eggs, dairy, breads, cereals, and nuts. Brazil nuts contain the highest level of selenium with up to 91 micrograms.
Dual Properties of Vitamin E
Vitamin E also helps to boost the production of certain immune system cells. Vitamin E helps to protect cells from damage and also boosts the production of certain immune system cells, both of which help to improve the body’s overall immunity.
Some Benefits From Vitamin C
Covid-19 is a novel coronavirus disease that has caused a worldwide pandemic of respiratory illness. Preliminary studies suggest that vitamin C may help reduce the severity of the disease. Clinical trials are currently underway to investigate the impact of vitamin C transfusions on patients with Covid-19.
Some experts are not enthusiastic about praising the benefits of vitamin C because the reviews of studies to date have only found a mild beneficial effect compared to a placebo.
The Sunshine Vitamin
The evidence on vitamin D’s ability to boost immunity is mixed, just like with vitamin C, Meydani said.
“We can’t say that giving higher levels of vitamin D is going to improve your immune response and fight respiratory infections,” she said. “Some studies have shown some benefits, but others have not confirmed them.”
People who have darker skin or who live in areas with little sunshine might be deficient in vitamin D, as are the elderly and exclusively breastfed babies. Many foods in the Western diet are supplemented with vitamin D, and taking too much of it can be toxic.
Steps to Help Support a Healthy Immune System
- Eat a balanced diet with whole fruits, vegetables, lean proteins, whole grains, and plenty of water. A Mediterranean Diet is one option that includes these types of foods.
- If a balanced diet is not readily accessible, taking a multivitamin containing the RDA for several nutrients may be used.
- Don’t smoke (or stop smoking if you do).
- Drink alcohol in moderation.
- Perform moderate regular exercise.
- Aim for 7-9 hours of sleep nightly. Try to keep a sleep schedule, waking up and going to bed around the same time each day. Our body clock, or circadian rhythm, regulates feelings of sleepiness and wakefulness, so having a consistent sleep schedule maintains a balanced circadian rhythm so that we can enter deeper, more restful sleep.
- Aim to manage stress. This is easier said than done, but try to find some healthy strategies that work well for you and your lifestyle—whether that be exercise, meditation, a particular hobby, or talking to a trusted friend. Another tip is to practice regular, conscious breathing throughout the day and when feelings of stress arise. It doesn’t have to be long—even a few breaths can help. If you’d like some guidance, try this short mindful breathing exercise.
- Wash hands throughout the day: when coming in from outdoors, before and after preparing and eating food, after using the toilet, after coughing or blowing your nose.
