10 vitamins & minerals to strengthen our immune system

Our immune system is our first line of defence against infections and other external and internal attacks, and is made up of three distinct layers, which are deployed depending on the nature of the threat:

• Physical barriers: e.g. skin, lungs, gastrointestinal and respiratory tracts.

• Biochemical barriers: e.g. secretions, mucus, and gastric acid.

• Immune cells: e.g. T and B cells which produce antibodies to target and destroy the pathogen.

Several factors can influence the effectiveness of the immune system, such as our life stage, the type, prevalence, and severity of the infection, and whether our immune function has been compromised, for example by antibiotics or poor nutrition.

Age and immunity

As humans age, the immune system evolves from the immature and developing immune responses of an infant, to an immune function that is potentially at its peak in adolescents and young adults, followed by a gradual decline in immunity in older people. Age-related changes are compounded by lifestyle factors such as diet, environment, and oxidative stress, which can influence and modify and in some cases, suppress immune function. Accordingly, the risk and severity of infections such as the common cold and influenza, pneumonia and diarrheal infections also vary over a lifetime.

Nutrition and immunity  

An adequate store of vitamins and minerals is essential for a strong immune system, particularly vitamins A, B6 & B12, C, D, E, copper, folate, iron, selenium, and zinc, otherwise the body is susceptible to infection. However, studies have found that despite having access to an abundant supply of healthy foods, a form of malnutrition is increasingly common in affluent countries, which is weakening our immune systems and leaving us vulnerable to attack. The consumption of a Westernized diet high in refined and processed foods, sugary drinks, and meat and dairy products, which is also low in fibre, fruits, and vegetables, does not provide us with the recommended levels of these essential vitamins and minerals.

Micro-nutrient malnutrition

Deficiency symptoms for many vitamins and minerals are non-specific and may present as fatigue, irritability, aches and pains, and heart palpitations. As well as impaired immunity, a prolonged, inadequate intake of essential micronutrients includes impaired growth and night blindness from vitamin A deficiency, impaired wound healing and bleeding from vitamin C deficiency, anaemia from iron deficiency, and rickets and osteomalacia from vitamin D deficiency. Deficiencies in the B vitamins lead to different types of anaemia: folate deficiency leads to megaloblastic anaemia, vitamin B6 deficiency results in microcytic anaemia, whereas vitamin B12 deficiency causes pernicious anaemia, and may result in neurological damage due to impaired myelination. An adequate combination of micronutrients is also required for many important processes in the body. For example, erythropoiesis requires not only iron, but also folate, vitamin B12, and vitamin A, and dietary vitamin C can improve the absorption of iron.

Who is at risk?

Economic, educational, ethnic and cultural backgrounds influence our diet and may adversely affect an individual’s micronutrient status. In the United States, research found that nearly one-third (32%) of the U.S. population is at risk of deficiency in at least one vitamin, or has anaemia. See the full report here. The mapping of micronutrient intake across Europe can be found here.

One vitamin where there is universal concern in terms of intake is vitamin D, however, the consequences of a deficiency can vary from country to country. People living in northern latitudes need to obtain the majority of their vitamin D from their diet, whereas those living in warmer climates can more readily obtain it from conversion through their skin stimulated by UV radiation.

Can a weakened immune system be revived?

The good news is that immune function may be improved by restoring deficient micronutrients to recommended levels, thereby increasing resistance to infection and supporting faster recovery when infected. Diet alone may be insufficient, and tailored micronutrient supplementation based on specific age-related needs may be necessary. See here for more information.

Here is a list of the key micro-nutrient vitamins and minerals that experts currently believe are most likely to strengthen the immune system, and the foods that contain the highest concentrations;

Vitamin A plays a key role in making and activating antibodies that neutralize unwanted bacteria and other micro-organisms, and is found in dried apricots, carrots, leafy green vegetables, red peppers, and sweet potatoes.

Vitamin B6 is required for the synthesis and metabolism of amino acids and lipids, and is in bananas, cauliflower, dark green leafy vegetables, red peppers, and sweet potatoes.

Vitamin B12 is required for proper red blood cell formation, neurological function, and DNA synthesis. It’s found in animal products, fortified breakfast cereals, and nutritional yeasts.

Vitamin C is probably best known as an antioxidant and is in most fruit and vegetables, particularly citrus fruits and dark green leafy vegetables.

Vitamin D is one of several hormones involved in the maturation of white blood cells that fight most types of infection. It’s produced by the skin when exposed to sunlight, and is also found in fortified margarines, breakfast cereals and soya milks. 

Vitamin E is an anti-oxidant that has been shown to enhance immunity and decrease susceptibility to certain infections, especially in the elderly. It’s found in almonds, asparagus, dark green leafy vegetables, red peppers and sunflower seeds.

Copper plays an important role in the development and maintenance of immune system function, and is found in asparagus, beans, chickpeas, lentils, spinach, and soya and tofu products.

Folate is required for the synthesis and metabolism of nucleic acids and amino acids, and is in beans, chickpeas, lentils and spinach. And the synthetic form, folic acid, is found in fortified breakfast cereals.

Iron is essential for keeping our bodies supplied with oxygen and is found in dark chocolate, dark green leafy vegetables, dried fruit, pumpkin seeds and turmeric.

Selenium plays a key role in the body’s detoxification system, and is in asparagus, brazil nuts, beans, chickpeas, and whole grains.

And finally, Zinc is critical for the normal development and function of blood cell production and boosts our ability to fight infection. It’s found in asparagus, beans, mushrooms, pumpkin and sesame seeds, and regular dietary intake is important because zinc can’t be stored in the body.

Vitamin and mineral supplements

Getting nutrients from foods like nuts, fruits, and vegetables is vastly superior, and far more satisfying than getting them from a tablet or tonic. However, it’s not always possible to achieve good nutritional status via the diet alone. In developing countries, for example, it may be difficult to find an adequate and varied supply of food, and in industrialised nations, where healthy, nutritious food is easier to obtain, people’s lifestyles may adversely affect their micronutrient status. In these circumstances, multivitamin supplements have the potential to improve immune function for a relatively small cost.

Thank you for reading this blog post. If you have any tips or information that you’d like to share, or ideas for future posts, please do let me know. I would love to hear from you.