Diet and the Immune System: What You Should Know

Increasing the biodiversity of the intestinal microbiota through diet may be key to improving the functioning of the immune system.
Diet and the Immune System: What You Should Know
Saúl Sánchez

Written and verified by el nutricionista Saúl Sánchez.

Last update: 01 April, 2021

Diet is a fundamental element in controlling the function of the immune system. If there isn’t an optimal supply of nutrients, then the body’s defenses will be diminished, which will, in turn, increase the risk of contracting infectious diseases.

However, the problem goes even further, as an inadequate diet can increase the incidence of autoimmune or complex diseases.

Diet isn’t the only element capable of modulating the action of the immune system; exercise and rest are also key factors.

Key nutrients for the immune system

The first thing we need to make clear is that there are certain nutrients that fulfill a special function within the immune system, and so they must be included in the diet on a regular basis. We’re talking mainly about vitamin C, vitamin D, and zinc.

Vitamin C

Diet and the immune system are very important.
Orange juice is an excellent source of vitamin C.

This water-soluble element is found in several different vegetables, such as strawberries, spinach, kiwi, citrus fruits, and tubers. It’s a key micronutrient for many different processes, among them collagen synthesis. This is the main protein in our bodies.

But, in addition, vitamin C plays an essential role when we look at the immune system, according to a study published in the journal Nutrients. This substance improves the defense function, as well as preventing the development of complex pathologies that have oxidation as an underlying mechanism. Here we could cite several types of cancer.

According to research published in the journal Frontiers in Immunology , vitamin C even reduces the incidence of flu and the common cold, in addition to reducing the severity of symptoms and improving the management of the infection.

These same beneficial effects extend to other diseases caused by viruses that affect the respiratory system, such as COVID-19.

In fact, some authors recommend its supplementation on a regular basis to ensure that you’re getting the recommended amount of the nutrient, which is usually around one gram a day.

It should be noted that, as it’s a fat-soluble element, its consumption must be carried out on a daily basis, as it’s excreted in the urine almost constantly. Likewise, it’s nearly impossible to overdose on it, and it’s considered to be a very safe nutrient for our health, even in high amounts.

Vitamin D

Vitamin D can be obtained in two ways: through endogenous synthesis from exposure to sunlight or through diet. Foods such as eggs, oily fish, enriched dairy products, and some mushrooms contain it, although usually in fairly low doses.

The truth is that this nutrient has been shown to be able to benefit bone health, reducing the risk of fractures during adulthood. This is due to its effect on increasing the absorption of calcium at an intestinal level, which generates a positive impact on bone metabolism.

Likewise, vitamin D also improves the functioning of the immune system. This is evidenced by a study published in the journal Reviews in Medical Virology, where an optimal level of the nutrient in the body is related to a lower risk of contracting pathologies related to the respiratory system.

But not only is vitamin D capable of reducing the incidence of infectious diseases, but it also enhances the body’s defense system when it comes to reducing the risk of developing chronic problems.

According to research published in the journal Reviews in Endocrine & Metabolic Disorders , maintaining low levels of the nutrient in the body is associated with a higher prevalence of diseases such as cancer or cardiovascular disease.

It’s essential to avoid vitamin D deficiencies

To prevent yourself from suffering from a vitamin D deficiency, in addition to adjusting your diet, it’s recommended to expose yourself to sunlight on a frequent basis. It’s important that this exposure is regular, progressive, but avoiding the hottest hours of the day. Avoiding burns is essential, otherwise you’ll soon have problems related to your epidermis.

It should also be noted that the inclusion of a vitamin D supplement in the diet can be considered to compensate for deficiencies at the dietary level. However, this should be recommended by a specialist.

Although there are often cases of overdoses due to the intake of this nutrient, it’s still considered to be very safe. However, it’s always advisable to have professional supervision.


Zinc is the last of the 3 key elements when it comes to diet and the immune system. This mineral is found in foods such as red meat and nuts, but always in small amounts.

It takes part in the physiological processes that have to do with the production of testosterone at the testicular level –  in men, of course. This can be a decisive factor in people who have a deficit in this hormone, as this can be conditioned by an insufficient intake of zinc at the dietary level.

In addition, and according to research published in Nutrients, zinc is also involved in the differentiation processes of white cells. These are the ones in charge of starting the processes related to the immune system, thus generating protection against the development of chronic and contagious diseases.

Although supplementation with the mineral is also possible, it isn’t frequent. When a varied and balanced diet is followed, it’s rare for a deficit of this nutrient to occur. Because of this, supplementation is more focused on people who have low levels of testosterone without any apparent cause.

Gut microbiota, diet, and immune system

Another element of key importance in modulating the activity of the immune system is the intestinal microbiota. In addition, this organ can be influenced through diet, as it’s sensitive to variations in the supply of nutrients and substances.

In this sense, its always recommended for people to have a competent microbiota with high biodiversity in order to promote the defense function of the body. It should be borne in mind that this element is one of the first entry barriers for any pathogen in the bloodstream. A failure in its function could result in a greater facility to fall ill.

The good news is that, from a dietary point of view, there are several things that can be done in order to ensure its functionality and diversity. The first of these is the inclusion of fermented products in the daily diet, such as yogurts and kefir.

It’s also important to ensure adequate fiber intake. According to a study published in The British Journal of Nutrition, this element has the ability to stimulate the growth of bacteria in the intestine as it’s its main energy substrate.

In addition, its fermentation generates a series of short-chain fatty acids that reduce systemic inflammation.

We mustn’t forget that it’s also possible to follow supplementation with probiotics to improve the health of the microbiota. This strategy is useful in order to increase the function of the immune system, making it less susceptible to errors that can cause the development of pathologies.

Whatever the case, we recommend that you consult a professional before resorting to a product of this type.

Other habits that impact the immune system

Diet and the immune system are not the only important aspects.
There are also other healthy lifestyle habits that boost the immune system!

In addition to diet, there are another series of habits or behavior that can have an impact on the immune system, thus increasing its efficiency. We have to highlight, first of all, physical exercise.

Despite the fact that intense and specific sports practice produces a temporary reduction in the body’s defenses, exercise as a habitual element increases immune function. Above all, it’s advisable to prioritize strength work, although resistance work has proven to be very useful in improving cardiovascular health.

Likewise, it’s key to get adequate rest at night. Sleeping less than 7 hours could negatively affect night repair work, which produces inefficiencies at a functional and physiological level.

In this sense, we must prioritize what we call sleep hygiene, which includes avoiding the use of electronic devices before going to sleep. It’s also essential to plan suitable schedules regarding going to bed early.

Finally, and in order to improve the efficiency of the immune system, you need to do all you can to stay away from stressful situations. These can alter hormonal production cycles, leading to an increased risk of developing pathologies.

Social relationships are a conditioner capable of modulating stress and mood. It’s recommended to seek healthy ones and avoid toxic ones.

Following a varied and balanced diet can improve the functioning of the immune system. This is achieved through an adequate supply of nutrients. Although we have focused on the micro kind, we mustn’t neglect the presence of macronutrients, such as quality proteins and fats.

It should be borne in mind that modulating inflammatory levels can be key in order to maximize the body’s defense function. In this sense, it’s important to ensure the contribution of unsaturated fatty acids, such as those of the omega 3 series. Guaranteeing the presence of phytonutrients with an antioxidant character can also be important.

Finally, don’ forget to practice physical activity on a regular basis, as well as to get at least 7 hours of sleep each night. With both habits, you’ll ensure that the body will perform its physiological functions properly.

Ensuring nighttime recovery also prevents possible alterations in the hormonal system, which would affect all the tissues and organs in the human body.

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