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Do you know the immune system as well as you think?


A good understanding of nutrition, health and well-being is vital for making the most out of your busy lifestyle; immune health is no exception. We surveyed over 300 Brits (Revive Active, 2023), and surprisingly, nobody could answer all of our immunity questions correctly.

Unfortunately, we aren’t as well educated on immune health as we should be. Here, we address four common immunity misconceptions. Then we explain which factors can affect the immune system and which vitamins you need to consume daily for optimal immune health. We discuss where you can find the best sources of immune-boosting vitamins and whether you may benefit from supplements.

Common misconceptions about the immune system

Oranges are the best source of vitamin C.

The vast majority of the UK believes that oranges are the best source of dietary Ascorbic Acid. Although oranges and citrus fruits are high in vitamin C, there are better sources, including yellow bell pepper.

Oranges hanging from a tree

Eggs are a good source of vitamin D.

Eggs contain some vitamin D; however, their content dwindles compared to fatty fish. If you are vegetarian, you will want to opt for organic eggs to boost your intake. If you are vegan, consider taking a vitamin D3 supplement.

Plant-based sources are higher in Zinc than animal-based sources.

Many people we surveyed believed that pumpkin seeds were higher in Zinc than animal-based sources. Vegans may want to pay particular attention to Zinc supplementation for the immune system.

Iron and vitamin E are primary nutrients involved in the immune system.

According to our survey (Revive, 2023), many people believed these nutrients were involved in the immune system. While iron and vitamin E is involved in many essential processes, they do not directly contribute to immune function. You would be better off turning your attention towards vitamin B12 or B6 – in fact, less than 50% knew these contribute to normal immune function.

Which factors can impact the immune system?

Here, we discuss the lifestyle factors that can impact the immune response.


Most were correct in thinking older adults have a weakened immune system. Immunosenescence occurs with age, whereby the immune response downregulates to prioritise other functions.

You may also be aware that young children can have a weak immune system. A child’s immune system does not fully develop until seven or eight. Children and older adults need to maintain a healthy immune system.

Statistic reading ‘31% knew which four lifestyle factors significantly influence immune function’. Icons depicting stress, sleep, diet and exercise circle the statistic.


Many of you knew which lifestyle factors impact the immune system. The most common lifestyle factors to affect your immune system are your diet (explored next), sleep, stress and exercise. Adequate sleep is essential for normal immune function, while high stress can impair immune function. Exercise in sedentary individuals has also been associated with immune function improvements. On the other hand, regular, intense exercise has been linked with immune function impairments for several hours after strenuous exercise.


Your diet is probably the most crucial factor in maintaining immune health. The immune system relies on many vitamins and minerals, and you must consume the proper amount each day to support normal immune function. Unfortunately, many of us do not have the time to eat a healthy, balanced diet all the time. Meanwhile, others may not know which foods to eat to support the immune response. This is where immune supplements can be helpful.

Which vitamins should you take for the immune system daily?

Knowing exactly which nutrients we need to support the immune system can be challenging. Here, we cover which vitamins and minerals are essential for a strong immune system.

  • Vitamin Cis required for fifteen different enzymes and is involved in the adaptive and innate immune system.
  • Vitamin D (vitamin D3) – is synthesised in the skin by UV light exposure; vitamin D3 is also involved in immune regulation.
  • Zinca cofactor necessary for over 300 enzymes also contributes to the normal function of the immune system and immune cells.

Vitamin B12, B6, Folic Acid (B9), Copper and Selenium all contribute to the normal function of the immune system. Healthy eating and supplementation will help you reach your nutrient goals.

What are the best sources of immunity vitamins and minerals?

Most brits could benefit from learning more about immunity-boosting foods since no one was aware that yellow peppers were, in fact, the best source of dietary vitamin C. Many also weren’t aware that oysters are the highest in Zinc compared to pumpkin seeds, dark chocolate and beef liver. Finally, fatty fish is the best source of dietary vitamin D, with over seven times the amount compared to eggs (per gram). Below we discuss the best sources of immune-supporting nutrients.

Statistic reading ‘0% knew that yellow peppers were the highest in vitamin C. Yellow, orange and red peppers are on three podiums, yellow is on the top.

Vitamin C

Yellow peppers are a great source, with 183mg per 100g. Adults only need 80mg of vitamin C daily, so one portion of yellow pepper would exceed your daily requirements.

Vitamin D3

D3 is only available from animal sources and is preferable over D2. The best sources of vitamin D3 are fatty fish, cod liver oil or beef liver. Mackerel (a fatty fish) contains 643IU of vitamin D per 100g; eggs contain only 87IU. Adults need 400IU daily.


Zinc is abundant in animal products, including red meat and beef liver, but interestingly, it is the highest in oysters. One oyster contains your total daily zinc requirements. Alternatively, 100g of beef can have 4mg of Zinc, around half of your daily needs.

Do you need immunity supplements?

Specific individuals may particularly want to look for immunity supplements, including older adults, vegans or adults with a limited diet. Busy, active adults may also benefit from the convenience of dietary supplementation.

Look for vitamins C, D, Zinc, B vitamins, copper and selenium for immune health and consider a powdered supplement for optimal nutrient delivery. Zest Active contains 25 active ingredients for immune support, energy, cognitive function and muscle function. Our wellness powder contains l-theanine, l-glutamine and taurine and is free from fillers, binders, caffeine and sugar.

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