The Foundation of a Balanced Diet and the Chinese Nutrition Guidelines: Ten Golden Rules for Scientific Nutrition

The human body needs more than 40 nutrients from its diet, and a deficiency in any one of them is detrimental. Severe deficiency in any essential nutrient can affect health and even endanger life. In the 16th century, thousands of British soldiers suffered from a bleeding disorder during a circumnavigation of the globe, resulting in numerous casualties. It was later discovered that giving the soldiers lemon juice could treat this disease, which was scurvy. Subsequently, vitamin C was isolated from lemons. Therefore, vitamin C is also known as ascorbic acid. Excessive intake of any nutrient is also harmful. An excess of one nutrient can interfere with the absorption of other nutrients and may even cause poisoning.

For example, excessive intake of vitamin A can lead to both acute and chronic poisoning symptoms. It has been reported that a father and his two sons from Northeast China ate a whole dog liver and experienced dizziness and peeling skin, diagnosed with vitamin A poisoning, as dog liver contains high levels of vitamin A. The Chinese Nutrition Society recommends both adequate daily intake of nutrients and maximum intake limits for each nutrient to prevent excessive consumption. A balanced diet is essential. Different foods contain different nutrients, and apart from newborns who can survive for several months solely on breast milk or formula, no other natural food can meet all the body's nutritional needs. Therefore, a reasonable combination and appropriate consumption of various foods are necessary to meet individual requirements.

The human body needs to maintain a balance between energy intake and energy expenditure. For adults, if daily energy intake is less than energy expenditure, they will become thin; conversely, if energy intake exceeds energy expenditure, the excess energy will accumulate in the body as fat, leading to overweight and obesity. For children and adolescents, a portion of their energy intake should be used for growth and development. To help the public adopt a balanced diet to obtain adequate nutrition and promote health, the Ministry of Health issued the "Dietary Guidelines for Chinese Residents 2007." Based on recent scientific research findings, it provides 10 guiding opinions addressing the nutritional needs of Chinese residents and the main problems in their diets.

The 10 points of the "Guidelines" are: 1. Eat a variety of foods, with grains as the staple and a mix of refined and whole grains; 2. Eat more vegetables, fruits, and tubers; 3. Consume dairy products, soybeans, or their products daily; 4. Regularly eat appropriate amounts of fish, poultry, eggs, and lean meat; 5. Reduce the amount of cooking oil used and eat a light, low-salt diet; 6. Do not overeat, exercise daily, and maintain a healthy weight; 7. Distribute meals reasonably and snack in moderation; 8. Drink enough water daily and choose beverages wisely; 9. Limit alcohol consumption if you drink alcohol; 10. Eat fresh and hygienic food.

We need to consume enough fruits and vegetables. Recently, the Ministry of Health launched an education program on "balanced diet," primarily advocating for increased intake of fruits and vegetables. Fruits and vegetables are rich in dietary fiber and are almost the sole source of vitamin C and carotene in the diet. They also contain abundant minerals and various phytochemicals beneficial to health and disease prevention. Adults should ideally consume 400-500 grams of fresh vegetables and more than 200 grams of fruit daily. However, the actual intake of Chinese residents is far below this, with the average person consuming less than 300 grams of vegetables and only 50 grams of fruit per day. Therefore, it is crucial to promote this concept more vigorously.

Yellow and red fruits (such as papaya, apricot, and mango) are high in carotene. For example, 100 grams of mango flesh contains up to 8 milligrams of carotene, equivalent to twice the recommended daily intake for adults. Dates, citrus fruits, and berries are high in vitamin C. 100 grams of fresh dates contain more than 200 milligrams of vitamin C, and eating just 50 grams of fresh dates a day can meet the recommended daily intake of vitamin C. Vegetables are more diverse than fruits, especially dark leafy greens, which are high in calcium, vitamin B2, carotene, and vitamin K, making them an important source of these nutrients in the diet. The content of certain nutrients can vary significantly between dark-colored and light-colored vegetables.

For example, dark leafy green vegetables can contain several times more calcium and vitamin B2 than light-colored vegetables, and dozens of times more carotene. Vitamin K is now known to be crucial for bone health. Dark green leafy greens are also the best dietary source of vitamin K; 100 grams of spinach and broccoli contain as much as 394 micrograms and 178 micrograms of vitamin K, respectively, while 100 grams of white radish, bananas, milk, eggs, and flour contain less than 1 microgram of vitamin K.

Surveys indicate that while the average daily intake of vitamin K meets the recommendations of the Chinese Nutrition Society, individual differences are significant, with one-third of respondents not consuming enough daily. Therefore, it is important to increase the intake of dark green leafy vegetables, which are high in vitamin K. Fresh vegetables and fruits are the best cancer-preventive foods. Extensive research evidence shows that high consumption of vegetables and fruits can reduce the risk of cancers in the mouth, lungs, esophagus, and gastrointestinal tract. This is mainly related to the nutrients and non-nutrient active chemical components contained in vegetables and fruits.

Moreover, some non-nutrient components may have a greater effect than nutrients. These non-nutrient phytochemicals, such as sulfur-containing compounds like allicin and dithioketones in allium vegetables, isothiocyanates in cruciferous vegetables, and polyphenols and flavonoids widely found in fruits and vegetables, all have anti-cancer effects supported by relevant animal experiments or epidemiological studies. It seems that the anti-cancer effects of fruits and vegetables are likely the result of the combined effects of multiple components.