Diet and the Immune System

The efficiency of an individual’s immune system is determined not only by genetic factors but also—and apparently with perhaps an even greater impact—by lifestyle, hygiene, and diet.

The current emergency caused by the COVID-19 pandemic has drawn extraordinary attention to the behaviors we should adopt to protect ourselves from infection.

Strangely, however, the media has devoted relatively little attention to the possible correlations between diet and immune defenses, and thus also to related recommendations regarding dietary choices and behaviors.

Undoubtedly, this is a major oversight.

In fact, diet can play a significant role in both strengthening and weakening the immune system.

Many studies show that both malnourished individuals and those who eat an unbalanced and unhealthy diet—that is, neglecting protective foods such as vegetables, fruits, whole grains, and legumes, and instead indulging in foods high in saturated fats and simple sugars—are more susceptible to illness and infection.

The quantity and quality of one’s diet, along with a healthy lifestyle, are also crucial for maintaining a strong immune system.

However, it is unclear whether certain vitamins, minerals, and other substances—such as specific fatty acids—actually play a role in improving the functioning of certain aspects of the immune system.

With this in mind, it is reasonable to encourage the consumption of these foods, which are indeed good sources of those specific nutrients.

They are listed below:

• Vitamin C (citrus fruits, strawberries, kiwis, green vegetables)
• Vitamin A (eggs, fish, milk, yellow and green vegetables)
• Vitamin D (eggs, fish, milk, and dairy products)
• Zinc (whole grains, fish, meat, and nuts)
• Selenium (whole grains, Brazil nuts, fruits, and vegetables)
• Omega-3 fatty acids (fish, flaxseed oil, and olive oil)

Foods that weaken the immune system:

• alcohol
• coffee
• saturated fats (fried foods)
• white flour and simple sugars

The gut microbiota plays a fundamental role in keeping the immune defense system located in our gut functioning efficiently at all times; this system is so important that it actually contains about 70% of all cells in the human immune system.

The microbiota is nourished and shaped by the food we eat every day.

In short, the gut microbiota changes—and quite rapidly—in response to changes in diet, which selectively influences the growth of certain types of microorganisms over others.