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Best Foods to Boost Your Immune System

Reading Time: 5 minutes 53 seconds


Date: 2021-11-22T00:00:00-05:00

The immune system is somewhat of a mystery. It is a complex interconnected system comprised of many organs performing a variety of functions. Typically, the immune system does a pretty good job defending our bodies against disease. But it isn’t perfect and sometimes it fails, and we end up sick.

Innate Immune System

The innate immune system is the body’s first line of defense. It is something that is natural and that we are all born with. The innate immune system is what viruses first come up against when they invade our bodies.

There are three barriers or defenses that make up the innate immune system.

  • Physical barriers such as the skin and eyelashes protect the body from organisms that can invade and cause infection.

  • Chemical barriers are defense mechanisms that destroy harmful invaders. Examples of chemical barriers are tears, mucous and stomach acid.

  • Cellular defenses identify harmful substances and take steps to neutralize or destroy them. Cellular defenses include natural killer cells like macrophages, neutrophils, basophils, and eosinophils.

The main purpose of the innate immune system is to immediately prevent the spread or movement of potentially harmful pathogens in the body. It is an immediate response that is fast-acting and non-specific. This means it does not respond differently based on the specific pathogen detected, it simply responds to flush out the invading cells.

Adaptive Immune System

The adaptive immune system is the body’s second line of defense. Adaptive immunity is often referred to as acquired or specific immunity. This is because it is not something the body is born with. Rather, it develops over time. The adaptive immune system is not an immediate response like the innate immune system. It is a specific and targeted immune system response that is long-lasting, highly specific, and sustained long term.

The hallmark of the adaptive immune system is the cloning and expansion of T and B lymphocytes (T cells and B cells). The first time the body encounters a new pathogen, it initiates a primary immune response. During this response, T and B cells create antibodies specific to the antigen present to destroy or neutralize it. This clonal expansion of lymphocytes is the hallmark of the adaptive immune system.

B cells also create memory cells. These are cells that survive for years and can protect the body during future exposure to the same antigen. It takes the body time to create antigen-specific antibodies the first time it is exposed. Therefore, response to initial exposure takes longer. However, when the body encounters that same pathogen a second time, the immune system’s response will be faster and more robust.

This speed is thanks to memory cells that keep note of previous invaders and have antibodies at the ready should they encounter it again. This memory is also what enables success with vaccinations. Vaccinations expose the body to a specific antigen. The body can then set to work crafting antibodies to fight the invader should it ever show face again.

Immune System Strength

Because the immune system is intricately complex, it can be challenging to test its strength or performance. Your clients can have a baseline blood test performed which can show whether antibodies are within the normal range. This can help determine if there are normal levels of infection-fighting proteins in the blood.

There are other signs and symptoms of a weakened immune system. Individuals that experience high levels of stress, or do not manage stress well may have a weakened immune system. Getting sick often can be a sign of a compromised immune system. Slow-healing wounds, feeling tired all the time and digestive issues such as loss of appetite, diarrhea, and abdominal cramping can also be indicators of a weakened immune system.

Foods to Boost Your Immune System

There is no one food, supplement, or cure that will prevent disease. However, certain lifestyle practices can help your clients develop a healthy immune system. Getting regular activity and eating a healthy nutrient-rich diet can help build a strong immune system. Below are some vitamins and minerals that can help promote strong immune health.

Vitamin C

Vitamin C is an essential water-soluble vitamin. It is an important antioxidant and has even been shown to regenerate other antioxidants within the body. Vitamin C has also been shown to increase the production of white blood cells that help fight viruses, bacteria, and foreign invaders. The body does not produce or store vitamin C because it is a water-soluble vitamin. It is therefore important to include vitamin C rich foods in the diet of your clients. And remember, Vitamin C is in more than just citrus fruit:

  • Red bell pepper

  • Broccoli

  • Spinach

  • Grapefruit

  • Oranges

  • Lemons and limes

Vitamin E

Vitamin E is a powerful antioxidant that helps fight off infection in the body. It is a fat-soluble vitamin involved in healthy immune function. Some foods rich in vitamin E include:

  • Wheat germ oil

  • Sunflower seed

  • Almonds

  • Peanuts and peanut butter

  • Hazelnuts

  • Sunflower or safflower oil

Vitamin A

Vitamin A is a fat-soluble vitamin involved in immune function, vision, reproduction, and cellular communication. There are two forms of vitamin A available in the human diet:

  • (1) Preformed vitamin A (retinol) found in foods from animal sources such as dairy products, lean meat (especially liver), and fish.

  • (2) Provitamin A or carotenoids which are pigments found in plants. One of the most important provitamin A carotenoid is beta carotene. When consumed, carotenoids are converted into vitamin A in the body. Carotenoids are better absorbed when cooked or eaten with sources of healthy fats.

When looking for vitamin A rich foods, think colorful. Common foods that contain both preformed vitamin A and carotenoids are:

  • Beef liver

  • Sweet potato

  • Pumpkin

  • Carrots

  • Spinach

  • Herring

  • Cantaloupe

  • Green tea

Vitamin D

Vitamin D, commonly known as the sunshine vitamin, is a fat-soluble vitamin. It is one of the most important and powerful nutrients supporting the immune system. Vitamin D can be found in the following foods:

  • Cod liver oil

  • Trout

  • Salmon

  • White mushrooms

  • Fortified cereal and fortified milk

  • Sardines

  • Green tea

Folate and Folic Acid

Folate and folic acid are different forms of vitamin B9. Folate is the naturally occurring form of vitamin B9. Folate is an essential nutrient that the body is unable to make on its own and must be consumed through the diet. Folic acid is a synthetic form of vitamin B9. It is often used in supplements and added to fortify processed food such as breakfast cereals and flour. Not all folic acid consumed is always converted into the active vitamin B9. Therefore, encourage your clients to consume folate-rich foods with naturally occurring vitamin B9. These foods include:

  • Legumes (beans, peas, and lentils)

  • Asparagus

  • Beef liver

  • Avocado

  • Spinach

  • Citrus fruits

  • Broccoli

  • Nuts and seeds


Iron is an essential mineral found in every single cell of the body. It is critical in the creation of the oxygen-carrying proteins hemoglobin and myoglobin. Iron also plays a part in many immune system processes. Some iron-rich foods include:

  • Red meat

  • Chicken

  • Turkey

  • Beans

  • Tuna

  • Broccoli

  • Oysters


Selenium is a mineral touted for its antioxidant properties. Food sources rich in selenium are:

  • Brazil nuts

  • Tuna

  • Cod

  • Meat and liver

  • Poultry

  • Cottage cheese


Zinc is an important nutrient that plays many roles in the body. It is required for many processes including wound healing and immune function. Zinc is needed for the healthy production of new immune cells in the body. Low zinc levels may lead to compromised immune function. Foods rich in zinc include:

  • Shellfish

  • Poultry

  • Red meat

  • Fatty fish like salmon

  • Chickpeas

  • Cashews

  • Green tea

At the end of the day, there is no special food, vitamin, or mineral that can prevent sickness and disease. However, by consuming a healthy vitamin and mineral-rich diet, your client can keep their body functioning at its best. Eating a healthy diet sets the body up for success in building a strong immune system and defense. Encourage your clients to try these food sources above. Consuming an adequate amount of naturally occurring vitamins and minerals will help build a strong immune system and keep your clients healthy and strong.

Looking for a fruitful career in fitness? When you become an ISSA Nutritionist, you can help improve the quality of your clients' lives beyond the gym walls. Unlock your career in health and fitness as an ISSA Nutritionist.

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