The life-long insights of one of China’s leading cancer researchers show that preventing cancer may be simpler than many people think—and it can start today.

Sun Yan, an academician of the Chinese Academy of Engineering, a clinical oncologist, and former director of the National Clinical Research Center for New Anticancer Drugs under China’s National Cancer Center (NCC), began his medical career in 1951. Over the past 60 years, he has devoted his life to the study and treatment of cancer.

Now 95 years old, Professor Sun remains physically healthy and mentally sharp. As a veteran oncologist, he has repeatedly shared his personal cancer-prevention principles with the public. According to him, these habits are neither extreme nor difficult, but they are consistently practiced.

Professor Sun firmly believes that a healthy lifestyle is the most effective “shield” against cancer. He strictly avoids the following four things:

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1. Fatty, Fried, and Processed Foods

Professor Sun follows a simple dietary rule: eat until about 70% full and stop as soon as you feel satisfied. He avoids animal fats, red meat, and fried foods, as these are known to increase the risk of cancer, particularly cancers of the digestive system.

According to a report from China’s National Cancer Center, insufficient intake of fruits and vegetables is one of the leading causes of cancer in China, accounting for 15.6% of major cancer risk factors—surpassing smoking and alcohol consumption.

Unhealthy foods act as “fuel” for cancer cell growth. The World Health Organization (WHO) has classified processed meats such as sausages, bacon, and ham as Group 1 carcinogens—meaning there is clear evidence they cause cancer. Regular consumption of these foods increases the risk of colorectal cancer by approximately 18%.

Red meat is also considered a high-risk factor. Frequent consumption of beef and lamb has been linked to reduced life expectancy and a higher likelihood of intestinal cancer. The risk becomes even greater when red meat is grilled or fried, as these cooking methods produce more carcinogenic compounds.

A simple but effective solution is to limit red meat and high-fat foods while increasing daily intake of vegetables and fruits. According to China’s Dietary Guidelines, adults should consume 300–500 grams of vegetables and 200–350 grams of fresh fruit per day, combined with moderate amounts of meat, to maintain nutritional balance and reduce cancer risk.

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2. No Smoking, No Alcohol

Professor Sun has repeatedly urged society to control tobacco use as strictly as drunk driving. He has witnessed many cancer patients quit smoking after hearing his advice—and often notes that quitting earlier could have prevented hospitalization altogether.

Cigarette smoke contains over 7,000 chemicals, including at least 69 known carcinogens such as nicotine, tar, and nitrosamines. The longer and heavier a person smokes, the greater the harm.

According to China’s 2020 Report on the Health Hazards of Smoking, approximately one million people die each year from smoking-related causes—more than the combined deaths from HIV/AIDS, tuberculosis, traffic accidents, and suicide.

Alcohol is also classified as a Group 1 carcinogen. Studies show that one in every 18 cancer cases is related to alcohol consumption, including cancers of the mouth, throat, liver, stomach, and more.

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3. Avoid Exposure to Cancer-Causing Infections

Not all cancers are caused by genetics or lifestyle alone—many are linked to infectious agents. According to The Lancet Global Health, approximately 2.2 million new cancer cases worldwide in 2018 were attributable to infections, accounting for about 13% of all cases.

Four major cancer-related pathogens deserve special attention:

• Human Papillomavirus (HPV): Responsible for over 90% of cervical cancer cases; transmitted through sexual contact or close skin-to-skin contact.

• Hepatitis B Virus (HBV): Can lead to liver cancer through chronic hepatitis and cirrhosis; transmitted via blood, sexual contact, or from mother to child.

• Epstein–Barr Virus (EBV): Associated with nasopharyngeal cancer; transmitted through saliva.

• Helicobacter pylori (H. pylori): Increases the risk of stomach cancer by 2–6 times; transmitted via oral or fecal routes. Poor hygiene, such as sharing utensils or not washing hands after using the restroom, increases infection risk.

Cancer itself is not contagious, but cancer-causing pathogens can be. Therefore, Professor Sun strongly emphasizes good personal hygiene, thoroughly cooked food, safe drinking water, and timely vaccination—such as the HPV vaccine.

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4. Avoid Being Trapped in Negative Emotions

“Don’t get angry. Don’t be stubborn. Don’t dwell on things. Learn to live with a lighter heart,” Professor Sun advises when speaking about mental health in modern life.

He describes himself as a carefree person who rarely becomes angry or distressed. In his clinical experience, many cancer patients share a common trait: long-term stress, depression, or emotional suppression.

Chronic psychological stress places the body in a constant state of tension, weakens the immune system, and creates an environment in which cancer cells can grow. Negative emotions such as anger, sadness, and resentment—when suppressed and left unresolved—can cause profound harm to the body over time.