How to help the immune system: the contribution of vitamin D

The immune system is the body’s defence against attacks from pathogens, such as viruses and bacteria.


The immune system consists of several components:

  • Organs such as bone marrow, the thymus gland, lymph nodes, spleen and lymphatic vessels
  • White blood cells, cells present both in the blood and in the tissues, subdivided into different subpopulations, specialised in the innate immune response (non-specific) and in the specific or acquired immune response, which is slowly induced by exposure to infectious agents or foreign molecules and which preserves the memory effect
  • Cytokines, mediators that act as chemical signals to regulate the immune response, coordinating cells and tissues involved in the immune response.

When the immune system detects an agent that is potentially harmful to the body, the immune response process is triggered: the cells of the immune system go into action to attack and neutralise the external agent

There are several causes that can lead to a weakening of the immune system and, consequently, to a condition in which you are more exposed to potentially harmful external factors.

Stress, for example, reduces the levels of white blood cells, weakening the body’s immune response which, therefore, is more vulnerable to attack by pathogens.

Ageing is another cause of potential reduction in immune system function, causing the body to gradually weaken.

Physical fatigue and exposure to adverse environmental conditions such as cold and wet weather also increase the risk of a drop in the body’s normal defences.

Some of the most frequent signs and symptoms indicative of a low immune condition are fatigue and difficulty concentrating:

The presence of these signs is an alarm bell for the normal functioning of the immune system: it’s therefore advisable to contact your doctor, who will analyse the situation and establish an appropriate treatment, if necessary.

Among the substances that support the immune system is vitamin D, a fat-soluble vitamin that is activated in the liver and kidney and also plays a key role in the absorption of calcium and phosphorus and in maintaining normal bones and teeth. To enjoy its benefits, it’s important that it’s present in adequate amounts in the body according to age: in children, adults, the elderly and menopausal women.

Unlike other vitamins, vitamin D is produced primarily by the body, through a process of biosynthesis that occurs in the skin, mediated by the UVB rays of the sun. In temperate latitudes, exposure to sunlight is sufficient to provide about 80% of vitamin D requirements.

Food can meet the remaining 20% of requirements, but few foods are rich in vitamin D: fish oil, particularly cod liver oil, liver and high-fat fish are the main dietary sources of vitamin D; egg yolk, milk and its derivatives contain smaller amounts.

In case of deficiency you can resort, on medical advice, to supplementation with vitamin D enriched foods and/or supplements.

Observing a healthy lifestyle is the first strategy to keep the immune system active and support the body’s defences. Some useful habits for maintaining an efficient immune system are, for example:

  • Regular physical activity, even moderate or light
  • Avoid or limit, as far as possible, stress
  • Do not smoke
  • Limit the consumption of alcoholic beverages as much as possible
  • Get enough sleep, dedicating an adequate number of hours per night to sleep and respect a regular sleep-wake rhythm
  • Follow appropriate personal hygiene measures to prevent infections

It’s essential, both in children and adults, to also follow a healthy and balanced diet, with the right intake of carbohydrates and proteins. The diet should include foods low in saturated fat and rich in omega-3 and omega-6 essential fatty acids, as well as ensuring an abundant daily intake of water and the right amount of fibre. In addition, it’s important to consume foods rich in vitamins and minerals, micronutrients that are essential for the metabolism and useful for several fundamental processes in the body.

Specifically, the vitamins and minerals that help maintain normal immune system function are, in addition to vitamin D, vitamins A, B6, B12, C, folic acid, iron, copper, selenium and zinc.

A diet that can help the immune system must therefore include the consumption of the right amount of fresh, seasonal fruit and vegetables, which contain large amounts of vitamins and minerals, but also legumes (beans, peas, broad beans, lentils and chickpeas), sources of protein, and cereals (wheat, corn, barley, rice, spelt, rye, oats), preferably whole grain.

Moreover, vitamins A, C and E, as well as selenium, copper and zinc, have antioxidant properties, i.e. they counteract the action of free radicals, which play a significant role in the ageing process.

Citrus fruit, kiwis, grapes, tomatoes strawberries and berries, as well as many vegetables, including broccoli, cabbage, spinach and peppers, are rich in vitamin C, while nuts, such as almonds, hazelnuts, peanuts, and vegetable oils are important sources of vitamin E. Vitamin A can be taken from melon, apricots, mango, papaya, pumpkin, carrots and green leafy vegetables.

When the body is deficient in one or more vitamins, this is referred to as vitamin deficiency or hypovitaminosis. In addition to improper diet, vitamin deficiencies can be caused, for example, by:

  • An increased vitamin requirement, e.g. during pregnancy or in growing and developing children
  • A reduction in absorption due to gastro-intestinal disturbances
  • Drug therapy
  • Alcohol abuse

In the event of a deficiency, you can resort, on the advice of your doctor or pharmacist, to specific vitamin food supplements that can ensure the proper intake of nutrients and, therefore, help support the proper functioning of the immune system.


Foods that increase the immune system

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