Every bite of food you eat contributes to your immune system

In the human body, the immune system is always on guard, defending against foreign invasion, removing aging or damaged cells, maintaining its own stability, and monitoring signs of invasion or danger. Nutrition is an important factor affecting the body's immune function. Epidemiological studies have shown that nutritional deficiencies can reduce the body's immune function and increase the risk of infection. A reasonable diet and adequate nutrition are the foundation of a strong immune system.

What mysteries can dietary nutrition research reveal for us? Is dietary nutrition actually related to the prevention and control of chronic diseases? Research shows that what kind of dietary pattern is healthier? In this issue, experts from the Institute of Nutrition and Health of the Chinese Center for Disease Control and Prevention will explain them to us one by one.

Research theme of "Nutrition and Immunity"

The history of research related to nutrition and immunity is long.

The discovery of the effect of nutrition on human immunity can be traced back to the 15th century. In 1497, Portuguese navigators found that even with adequate food supplies, many sailors who sailed for a long time still suffered from scurvy. It was not until 1933 that researchers successfully synthesized vitamin C and found that vitamin C deficiency was the root cause of scurvy. Although this is not a direct study on nutrition and immunity, it has been confirmed that insufficient food intake and nutrient deficiencies can lead to related diseases.

Since the late 1990s, people have been paying attention to the effects of food and its active ingredients on human immune function. In 2004, researchers began to pay attention to the relationship between dietary patterns and human immunity, and found a correlation between dietary patterns and markers of inflammation and endothelial dysfunction.

Inflammation and oxidative stress are closely related to the pathogenesis of various chronic diseases such as atherosclerosis, coronary heart disease, diabetes and metabolic syndrome, and are early indicators of pathological changes. In addition to the study of the relationship between nutrition and immunity, since 1996, the study of the effect of nutrition on inflammation or oxidative stress response has also become a new hot spot.

For hundreds of years, research on nutrition and human immunity has been gradually deepening. In recent years, with the continuous deepening of related research and the improvement of people's living standards and health needs, the role of dietary nutrition on immunity has attracted widespread attention.

Food intake is a direct factor affecting the nutritional status and health level of the human body. As early as the end of the 19th century, studies have found the correlation between the body's nutritional status and immune function. Many subsequent studies have also confirmed the role of dietary nutrients on the body's immunity by exploring the relationship between specific nutrients or foods and plasma immune index levels, or the impact on the risk of immune-related diseases.

Nutrient deficiency or insufficiency can affect immune function, while nutrient supplementation can reverse the decline in immune function caused by nutrient deficiency to a certain extent.

At present, research on the relationship between nutrients and immune function mainly focuses on vitamin A, vitamin D, vitamin E, fatty acids, iron and zinc.

Research on macronutrients and immune function mainly focuses on fats and fatty acids, among which n-3 polyunsaturated fatty acids (PUFA) are the main research object. Studies have shown that their intake is related to the risk of various acute and chronic nutrition-related diseases.

In the research on micronutrients and immunity, the deficiency of vitamin A, vitamin D and zinc will affect the humoral immunity and cellular immunity of the human body. From the results of intervention experiments, zinc supplementation can reverse the decline of immune function caused by zinc deficiency, but there is still a lack of positive evidence that iron supplementation can improve immune function.

Dietary patterns are an important entry point to explore immune function

In recent years, in studies exploring the relationship between diet and disease, dietary exposure assessment has undergone a shift from single nutrients or foods to food groups or dietary patterns.

Because some nutrients are highly correlated and the effects of individual nutrients are often small, it is difficult to directly study their effects on immunity. Nutrient intake levels are often determined by a combination of multiple foods and are potentially influenced by dietary patterns.

Dietary pattern is a dietary variable that comprehensively considers the types, intake, frequency and proportions of different foods and food groups. It can be used to assess the synergistic, cumulative and antagonistic effects between foods and nutrients in the overall dietary structure.

There are many studies at home and abroad that have explored the relationship between dietary patterns and human immune function and provided scientific evidence. These studies believe that dietary patterns can regulate the levels of various inflammatory markers, directly affecting the immune system, and can also indirectly affect the immune system by regulating metabolic indicators.

For example, studies have shown that the Mediterranean dietary pattern, which is mainly composed of vegetables, fruits, fish, whole grains, beans and olive oil, can reduce inflammatory responses and improve endothelial cell function, reduce chronic systemic inflammation, and has a positive impact on the risk of metabolic syndrome, cardiovascular disease and other chronic inflammatory diseases, and enhance the body's antioxidant capacity.

Healthy diet is of great significance to the prevention and control of chronic diseases

With the rapid development of my country's social economy, the burden of chronic diseases has become increasingly heavier and has become a major obstacle to social development. The "Report on the Nutrition and Chronic Disease Status of Chinese Residents (2020)" released by the State Council Information Office on December 23, 2020 shows that the current prevalence of hypertension among residents aged 18 and above in my country is 27.5%, the prevalence of diabetes is 11.9%, and the prevalence of hypercholesterolemia is 8.2%. The deaths of Chinese residents due to chronic diseases account for 88.5% of the total deaths.

Inflammation and oxidative stress are closely related to the onset of various chronic diseases such as atherosclerosis, coronary heart disease, diabetes and metabolic syndrome. Therefore, the levels of inflammatory factors and oxidative stress markers can be used as early markers of the risk of chronic diseases.

Nutritional intervention is of great significance for the prevention and control of chronic diseases.

Many domestic and foreign literatures on the effects of nutrition (including nutrients, food or dietary patterns) on the concentrations of inflammatory factors and oxidative stress markers in the body show that following healthy dietary patterns such as the Mediterranean dietary pattern, increasing the intake of vitamins (β-carotene, vitamin C, vitamin D, vitamin E, etc.), essential fatty acids (PUFA, etc.), certain essential amino acids, plant compounds mainly phenolic compounds, appropriate amounts of energy, dietary fiber, and the intake of lean meat, fish, shrimp, fresh vegetables and fruits, soybeans, nuts, etc. can all reduce the levels of plasma inflammatory factors and oxidative stress markers.

Unhealthy eating habits, such as excessive intake of trans fatty acids, cholesterol, and sugary drinks, can lead to increased levels of plasma inflammatory factors and oxidative stress markers.

Systematic studies have shown that a dietary pattern characterized by eating more whole grains, fresh vegetables and fruits, low-fat dairy products, less red meat or processed meat, refined grains and processed foods, and a diet rich in polyunsaturated fatty acids is beneficial to a variety of health outcomes.

Therefore, it is recommended that people start with healthy changes in food groups, gradually improve their daily bad eating habits, and find a dietary pattern that suits them and promotes health, thereby bringing greater benefits to their health.

Source: Healthy China