"Anti-inflammatory diet" is popular! What are anti-inflammatory foods and pro-inflammatory foods? Save them now!

Expert in this article: Li Lin, PhD in Food Science, Professor of Zhongshan College of University of Electronic Science and Technology of China, Food Safety Expert of Zhongshan City:

Many diseases that plague the human body share one common characteristic: inflammation.

Recently, many food bloggers have begun to introduce a magical "anti-inflammatory diet", claiming that it can enhance human immunity and reduce the risk of inflammatory infection.

There is not only an "anti-inflammatory diet," but there are also many foods that can increase inflammation. Are these eye-catching claims true?

What is the “inflammation” in an “anti-inflammatory diet”?

The "inflammation" in an anti-inflammatory diet is not the same as the "inflammation" caused by viruses or bacteria that we often talk about.

Inflammation is a defensive response of the body's own immune system to external stimuli. The immune system is like a guard protecting the body. When there is trauma or infection, the immune system will be activated and the guard will respond quickly, engulfing invading viruses and bacteria or clearing its own necrotic tissue. We call this inflammation caused by bacterial or viral invasion acute inflammation, which comes and goes quickly.

The "inflammation" in the anti-inflammatory diet refers to chronic inflammation, which is a low-level chronic inflammation caused by excessive production of various cytokines (interleukins, tumor necrosis factor TNF-α and interferon γ-INF, etc.) under stress or stress conditions.

This inflammation can develop gradually over months or years and affect the immune system, which is then in a state of protracted warfare, always alert but tired and irritable, and can easily go off accidentally.

This repeated and persistent immune response often causes damage to the body. Studies have shown that chronic inflammation is related to many chronic diseases, such as obesity, type 2 diabetes, cardiovascular disease, chronic respiratory disease, psoriasis, rheumatoid arthritis, cancer, etc.

A 32-year report involving 210,000 participants published in 2020 by the Department of Nutrition at the Harvard School of Public Health showed that cardiovascular health is related to the body's inflammatory state, and food can exacerbate or improve the body's inflammatory state.

What does an “anti-inflammatory diet” include?

Since different foods have different effects on inflammation in the body, it is necessary to understand the anti-inflammatory or pro-inflammatory effects of different foods.

In general, red meat, overly processed foods, and high-sugar, high-fat foods tend to cause more inflammation in the body.

Red meat contains a sialic acid molecule called Neu5Gc that is not found in the human body. It is recognized by the immune system as a foreign invader, thus causing inflammation. Animal experiments have shown that long-term and excessive consumption of red meat will increase the risk of cancer in mice.

Over-processed foods such as white bread, sugary drinks, salad dressings, processed meat products, etc. are generally high in sugar, salt, fat and contain a large amount of trans fatty acids, which can easily cause chronic inflammation in the body.

Food ingredients that can improve chronic inflammation include omega-3 fatty acids, polyphenols, dietary fiber and natural antioxidants; these substances can exert anti-inflammatory effects by blocking signals, inhibiting the expression of prostate cyclooxygenase, lowering the levels of inflammatory mediators and activating anti-inflammatory pathways. They can also indirectly produce anti-inflammatory effects by adjusting intestinal flora and producing short-chain fatty acids.

The biological activity of anti-inflammatory foods has been verified in cell and mouse models, but there is no conclusion in human studies. In 2021, a review was published in "Critical Reviews in Food Science and Nutrition". The research team screened 88 foods with anti-inflammatory effects from 3,581 studies, including: cranberries, grapes, pomegranates, strawberries, whole wheat products, low-value dairy products, yogurt, sesame seeds, flax seeds, soy foods, turmeric, etc.

Figure 1 Some foods that can reduce chronic inflammation

(Image source: Julissa Luvián-Morales et al. (2021). Functional foods modulating inflammation and metabolism in chronic diseases: a systematic review. Critical Reviews in FoodScience and Nutrition.)

Based on the above studies, researchers divided foods that may have anti-inflammatory functions into 6 categories:

Vegetables, especially cruciferous vegetables such as kale, cabbage, broccoli, etc.;

Fruits, especially berries such as cranberries, strawberries, blueberries, grapes, etc.;

Foods rich in dietary fiber such as whole grains and beans;

Foods rich in polyphenols and flavonoids such as green tea, soybeans, etc.;

Spices such as turmeric, ginger, cinnamon, nutmeg, sage and garlic;

Foods rich in omega-3 fatty acids include salmon, flaxseed oil, algae oil, grapeseed oil, rapeseed oil, nuts, almonds, etc.

Does an “anti-inflammatory diet” really work?

Although the term anti-inflammatory diet is very fashionable, it is not a specific dietary pattern. The Mediterranean diet, DASH diet (a salt-reducing diet for patients with hypertension), Okinawa diet, traditional Nordic diet and traditional Mexican diet are all anti-inflammatory diets.

These dietary patterns have the same characteristics: they are mainly based on plant foods, emphasizing the consumption of more fruits and vegetables, whole grains, foods rich in omega-3 fatty acids, lean meats and spices, etc.

Although the effect of diet on chronic inflammation has not yet been clearly quantified, some studies have shown positive effects. A 2016 study found that after one year of adopting an anti-inflammatory diet, the inflammatory factor CRP in the blood of patients with type 2 diabetes decreased by 37%; other diets based on fish, fruits and vegetables also had an inhibitory effect on inflammatory factors in cardiovascular patients.

These results are exciting, but the human body is very complex. To improve immunity and reduce the occurrence of chronic inflammation, we should not blindly believe in some legendary diet. In addition to a balanced diet, it is best to start from the following four aspects:

Exercise: 30 minutes of moderate exercise every day. Aerobic exercise is amazingly effective in boosting immunity.

Reduce stress: Long-term stress and tension will increase the body's inflammation level. Maintaining an optimistic attitude and good habits will help control the level of inflammatory factors in the body. Regular sleep can also help slow down the accumulation of inflammatory factors.

Control your weight: Obesity can lead to hormonal and immune system disorders and aggravate the occurrence of chronic inflammation. Therefore, balance your diet and exercise and maintain an appropriate weight and body mass index (BMI).

Get rid of bad habits and have regular physical examinations: Smoking and drinking are recognized as bad habits, both of which will cause an increase in the level of inflammatory cytokines in the blood; have regular physical examinations to detect potential risks to the body in a timely manner; if you have inflammation such as gastritis, pharyngitis, hepatitis, or have autoimmune diseases such as lupus erythematosus, arthritis, etc., you need a more detailed and scientific lifestyle and eating habits.

Allergies are also an important cause of chronic inflammation. Therefore, for people with allergies, eliminating allergens is an important way to resist chronic inflammation.

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