Introduction: As people start to pay more attention to the impact of diet on health, whether dining at home or ordering out, the emergence of various anti-cancer lists has led to a trend of overindulging in a single food deemed to prevent cancer. This approach, however, is not beneficial to health.
The anti-cancer effects of food are classified into four levels.
Similar to how carcinogens are classified, the anti-cancer effects of food are also graded. I believe that instead of looking at the myriad of anti-cancer rankings, it's better to refer to authoritative reports. In 2007, 21 experts from the World Cancer Research Fund and the American Institute for Cancer Research spent five years synthesizing evidence from epidemiological studies and other research on food, nutrition, physical activity, obesity, and cancer risk to produce the report "Food, Nutrition, Physical Activity, and the Prevention of Cancer." After evaluation and judgment, the expert group categorized the role of food in reducing cancer risk into four levels: "Convincing," "Probable," "Limited," and "No Convincing Evidence."
"Convincing" means there is sufficient evidence for a causal relationship in evaluating the reduction or increase of cancer risk, providing a solid basis for making cancer prevention recommendations. "Probable" indicates that, under normal circumstances, there is also sufficient evidence to make cancer prevention recommendations. "Limited" means the evidence is limited, making it impossible to draw a causal evaluation, and it's insufficient for making anti-cancer recommendations. "No Convincing Evidence" suggests that a causal relationship between the food and cancer prevention is unlikely. From a nutritional perspective, the evidence for the "Probable" and "Limited" categories is relatively more substantial.
"Probable" Level
The evidence for vegetables and fruits preventing cancer is relatively strong, and they can be said to prevent cancer to a large extent. However, their effectiveness depends on the levels of certain micronutrients. For example:
Foods rich in folate are probably effective in preventing pancreatic cancer. A dietary survey by the Japanese National Cancer Institute found that the daily folate intake from food was significantly lower in people with pancreatic cancer than in those without. The risk of pancreatic cancer in the top one-fifth of folate consumers was about half that of the bottom one-fifth. This is because folate helps maintain stable cell methylation, and low methylation levels can easily induce cancer. Foods rich in folate include animal livers, with chicken liver being the highest. Additionally, folate is abundant in green leafy vegetables such as spinach, lettuce, asparagus, rapeseed, and bok choy. Fruits with relatively high folate content include avocados, bananas, and papayas.
Avocado Egg Salad
Foods rich in carotenoids are probably effective in preventing oral and pharyngeal cancer. Taking oral cancer as an example, an epidemiological survey published in the *Journal of International Oral Medicine* showed that animal experiments, cell culture studies, and preliminary clinical trials have confirmed the potential preventive effect of beta-carotene on oral cancer. This is because carotenoids can enhance nutrient exchange between cells, activate damaged cells to maintain normal growth, and thus prevent cancer to some extent. Carotenoids mainly consist of carotene and lutein. You might be surprised that broccoli contains about twice as much carotene as carrots. In addition, wolfberry, sea buckthorn fruit, mango, pumpkin, water spinach, and other fruits and vegetables are also rich in carotene. Lutein is commonly found in egg yolks and corn.
Foods rich in lycopene are probably effective in preventing prostate cancer. A Harvard University study found a correlation between lycopene and prostate cancer. Men who consumed lycopene in their diet daily (more than 6.5 mg) had a 21% lower risk of developing prostate cancer compared to those with the lowest intake. Lycopene is not only found in tomatoes; it is also present in fruits like watermelon, persimmons, mangoes, grapefruits, and citrus fruits, as well as in tea leaves and the roots of vegetables like radishes and carrots. However, lycopene is better absorbed when cooked, making tomatoes the source of over 80% of the lycopene consumed by humans, with stir-fried tomatoes or soups being good options.
Foods rich in vitamin C are probably effective in preventing esophageal cancer. According to surveys, the vitamin C content in the blood of esophageal cancer patients was only 1/9 to 1/8 of that in residents from areas with low esophageal cancer incidence.
Furthermore, a recent joint study by Zhejiang University School of Medicine and Zhejiang University Translational Medical Research Institute showed that adequate intake of vitamin C helps prevent stomach cancer. Vitamin C can effectively prevent nitrates from turning into carcinogenic nitrosamines in the digestive tract and maintain the structural integrity of the cell matrix. Therefore, eating more fresh jujubes, citrus fruits, kiwis, peppers, pea shoots, and broccoli can help prevent esophageal cancer. The *2012 Chinese Dietary Guidelines for Residents* recommend an intake of 100 mg/day. If you live in an urban environment with excessive "negative nutrients" from electronic products, car exhaust, and heavy air pollution, your vitamin C intake should be increased to around 500-800 mg.
Tomato and Beef Stew with Potatoes
"Limited" Level
There is limited evidence that foods rich in selenium can prevent stomach, colon, and rectal cancer. Many years ago, German scientists discovered that selenium could cause malignant tumors in mice to regress. Another study from Arizona, USA, showed that people with high selenium levels in their blood had a 34% lower risk of colon cancer than normal individuals. It is speculated that selenium can increase the activity of selenium-containing enzymes in the human body and promote the repair of the gastric mucosa and the healing of ulcers. It is recommended that people with gastrointestinal problems supplement with selenium-rich foods, such as sesame seeds and malt. Seafood contains more selenium than meat, followed by the heart, kidneys, and liver of animals. Garlic and asparagus are also relatively rich sources of selenium among vegetables.
Foods rich in vitamin B6 or vitamin E may have a limited effect in preventing esophageal and bladder cancer. Experts at the University of Texas MD Anderson Cancer Center studied 468 bladder cancer patients and 534 cancer-free volunteers. The researchers found that people with a vitamin E-rich diet who also took supplements had a 44% lower rate of bladder cancer. Vitamin B6 can inhibit cancer cell formation to some extent, help synthesize some important enzymes in the human body, and regulate metabolism. It is found in large amounts in grains, beans, yeast, dried fruits, and animal内脏. Sunflower seeds are one of the foods richest in vitamin E. Other sources include nuts, whole wheat products, vegetable oils, salad dressings, legumes, spinach, mustard greens, green peppers, and red peppers.
Of course, cancer prevention cannot rely solely on the foods mentioned above; a balanced diet is crucial. According to the recommendations in the *Chinese Dietary Guidelines for Residents*, adults should eat 300-500 grams of vegetables daily, including a variety of vegetables, with at least half being dark-colored vegetables. They should eat 200-400 grams of fruit daily. I suggest that people's diet should be primarily plant-based; eat less red meat, including pork, beef, and lamb; avoid processed meat products; limit salt intake; and do not eat moldy grains or legumes. Nutritional needs should be met through a varied and balanced diet.
Celery and Stir-fried Pork Slices with Red Peppers