In biology, immunity refers to the body’s ability to defend itself against substances that threaten its proper functioning or survival. These “threats” can be of 3 types: microbes (viruses, bacteria, fungi, parasites), cells that have become cancerous or a foreign body (a splinter, as well as a transplanted organ).

It has long been known that with age or an illness, immunity weakens and the body becomes more vulnerable to infections. These often become more frequent and more serious. A common flu can then degenerate into pneumonia and be fatal in the elderly.

However, it is also noted that some apparently healthy adults with normal amounts of immune cells (according to blood tests) often contract infections such as colds or gastroenteritis. On the contrary, under similar conditions, others are more resistant to these illnesses. The difference would play out mainly in terms of lifestyle. Indeed, numerous data from epidemiological studies indicate that diet, smoking, sleep, physical activity, degree of stress, quality of human relationships and living environment all influence the quality of the immune response.

Thus, health and immunity are closely linked: taking care of your health on a daily basis improves your immunity, and vice versa. However, if at some point the body needs an external boost, there are a number of additional solutions that can be used.

Symptoms of a weak immune system

The following symptoms may be a sign of a weakened immune system.

• Persistent fatigue, which often hides chronic stress or a lack of sleep, two factors that weaken immunity.
• Increased susceptibility to infections, seen with frequent colds, urinary tract infections, herpes rashes, recurrent vaginitis, persistent wart, etc.
• Injuries that take time to heal .

People at risk

• People with chronic or serious illness: diabetes, lung disease, cardiovascular disorder, kidney disease, cancer, infection with the human immunodeficiency virus (HIV), etc.
• People undergoing or who have undergone certain treatment: for example, chemotherapy against cancer.
• Older people generally have an immune system that responds less quickly and less strongly to infections than middle-aged adults. Moreover, this explains why vaccination is less effective in them.
• People suffering from malnutrition. A diet that is not balanced in quantity or quality is the most important cause of immune deficiency around the world and makes the person affected vulnerable to several infectious diseases.
• People with a sedentary lifestyle..
• People who do not get enough sleep.
• People with chronic stress. One of the many effects of chronic stress on the body is to reduce the ability of the immune system to respond.
• People who have been exposed to toxins, including chemical household cleaners and herbicides on lawns, and from the consumption of fruits and vegetables sprayed with insecticides.
• People who have been exposed to outdoor air pollutants as well as those that spread inside homes (mold, bacteria, tobacco and combustion gases).
• Overweight and obese people. The immune functions appear to be damaged by excess fatty tissue, according to studies in humans and animals. Obesity has even been observed to increase the risk of contracting certain specific microbes, such as influenza (which causes the flu) and Helicobacter pylori (associated with peptic ulcers). Hormonal changes and the increased presence of pro-inflammatory substances could be to blame.

How to protect your immune system

• Nutrition is key

Severe malnutrition (marasmus) with calorie and protein deficiency is the main cause of immune deficiency. It is mainly found where poverty and famine are present.

In industrialized countries, micronutrient deficiency is increasingly common. The popularity of junk food partly explains this phenomenon. This form of malnutrition results from a lack of vitamins and minerals in the food we eat. Animal studies have shown that a deficiency of only one of the following micronutrients interferes with immune function: zinc, selenium, iron, copper, calcium, folic acid or vitamins A, B6, C and E2.

It is important to ensure that you are getting enough servings of fruits and vegetables, protein, and “good fats” each day. In stimulating the immune system, some vegetables seem to be more effective than others. This would be the case with mushrooms, especially shiitakes and oyster mushrooms. Garlic, onion and shallots are also preferred for their antimicrobial properties.

If you have signs of a weak immune system, it would be helpful to have a blood test and an assessment of your eating habits by a nutritionist.

• Exercise

We know the multiple benefits of regular physical activity: better cardiovascular fitness, good maintenance of muscle mass, normalization of blood pressure, weight control and reduction of several risk factors associated with chronic diseases.

In addition to promoting overall good health, exercise may also have a direct effect on immunity. By improving blood circulation, exercise allows various immune system substances to flow more easily through the body. This good circulation is essential to prevent infection of a wound, for example. In addition, it has been observed that certain immune components are stimulated by physical activity.

In older people, a few studies indicate that regular exercise helps prevent a decline in immune function. However, it is best to take it in moderation, as overtraining will cause upper respiratory tract infections, such as colds and flu.

• Stress management

Without a doubt, stress has an adverse effect on health whether it is present constantly or for a long time. Indeed, researchers interested in the link between stress and immunity do not focus on one-off, short-term stresses, but rather on frequent and constant stresses (for example, balancing the demands of work and family life or taking care of a sick loved one). Stress causes the release of stress hormones, such as cortisol and adrenaline. These hormones are very useful in the short term, but harmful if produced for a long time. They then directly harm the immune system by inhibiting the production of cytokines.

A few studies have shown that people caring for a loved one with Alzheimer’s disease have higher levels of cortisol and produce fewer antibodies in response to the flu shot. The researchers found that the effect of this stress on immunity was inversely proportional to the support from those around the caregiver.

To lower the level of stress, it is suggested to identify the situations that cause tension and look for ways to better cope with them (rather than avoid them). Consulting a psychologist or psychotherapist can be of great help.

Other important factors for health and immunity

• Set aside enough hours for sleep as needed (on average, a 7-hour night’s sleep is a minimum). Also, rest when your body tells you to.
• Do not smoke.
• Maintain a healthy weight, determined by your height (to calculate your healthy weight, take our Body Mass Index (BMI) and Waist Size test).
• Minimize the risk of food poisoning by taking proper precautions. Consult our Gastroenteritis and Diarrhea fact sheets to find out about preventive measures.

Medical treatments for people with weak immune system

Medicine offers a variety of drugs to treat infection or reduce the risk of it, as the case may be. Here are a few examples.

• Antiseptic lotions. They are applied promptly to minor wounds, cuts and scrapes. Their prolonged use is however not recommended, as it can cause the installation of strains of bacteria resistant to treatment.
• Antibiotics. Useful for treating bacterial infections or preventing contagion in some cases.
• Vaccination. It is a way of strengthening the immune system and improving the protection of individuals against certain infections. It sets up a specific immune memory. The duration of vaccine effectiveness varies depending on the type of vaccine. Consult our Vaccination file: current ideas and debates.
• Antivirals. These virus-inactivating drugs may be part of the treatment for a viral infection such as shingles or chickenpox in adults. They can also be given to people who are more fragile to prevent a viral infection or reduce its consequences, such as the flu.
• Medicines against parasites, such as Antimalarial medication. It is recommended that they be taken before traveling to an area of ​​the world where the risk of contracting malaria is high.
• The doctor may also choose to administer antibodies, especially in cases where it is necessary to strengthen the immune system on an emergency basis. This method, called serotherapy, provides short-lived immunity.

If there is a high susceptibility to infections, the doctor may determine whether it is a primary immune deficiency (linked to genes). In this case the symptoms are more pronounced and visible from childhood, especially with recurrent, serious, long-lasting and difficult-to-treat infections. Special treatments then apply.