Fresh vegetables and fruits are internationally recognized as disease-preventing and health-promoting foods. The "Dietary Guidelines for Beijing Residents" by the Beijing Municipal People's Government and the "Chinese Residents' Dietary Guidelines 2007" jointly recommend that vegetables—generally, darker are better than lighter, leafy parts are more nutritious than roots and stems, and leafy vegetables are superior to gourd vegetables.
Vegetables and fruits are important sources of vitamins, minerals, dietary fiber, and phytochemicals, with high water content and low energy. Diets rich in vegetables, fruits, and tubers play an important role in maintaining good health, normal intestinal function, boosting immunity, and reducing the risk of chronic diseases such as obesity, diabetes, and hypertension. Therefore, in recent years, dietary guidelines from various countries have emphasized increasing the variety and quantity of vegetable and fruit intake. Both the "Dietary Guidelines for Beijing Residents" and the "Chinese Residents' Dietary Guidelines 2007" recommend that Chinese adults consume 300-500 grams of vegetables daily, with dark-colored vegetables preferably accounting for about half, and 200-400 grams of fruit, while also paying attention to increasing the intake of tubers. The nutritional value of lettuce leaves, celery leaves, and radish greens is several times higher than that of their stems and roots.
Vegetables are an important source of micronutrients, dietary fiber, and natural antioxidants. Fresh vegetables generally contain 65%-95% water, with most vegetables having a water content of over 90%. Vegetables contain cellulose, hemicellulose, pectin, starch, carbohydrates, and most are low in energy, making them a category of low-energy foods. Vegetables are also good sources of carotene, vitamin B1, vitamin C, folic acid, calcium, phosphorus, potassium, and iron.
Vegetables from嫩茎, leaf, and flower categories, such as cabbage, spinach, broccoli, etc., are good sources of carotene, vitamin C, vitamin B2, minerals, and dietary fiber. Vitamin C is abundant in the metabolically active leaves, flowers, and stems of vegetables, parallel to the distribution of chlorophyll. Generally, darker vegetables have higher levels of carotene, riboflavin, and vitamin C than lighter vegetables, and also contain more phytochemicals. In the same vegetable, the vitamin content in the leaves is generally higher than in the roots and stems; for example, lettuce leaves, celery leaves, and radish greens are several times higher in vitamins than their corresponding stems and roots. The nutritional value of leafy vegetables is generally higher than that of gourd vegetables. Root vegetables have lower dietary fiber than leafy vegetables. Cruciferous vegetables, such as cabbage, cauliflower, and kale, contain phytochemicals like aromatic isothiocyanates, which are the main anti-cancer components. Fungi and algae, such as shiitake mushrooms, wood ear mushrooms, yeast, and seaweed, contain protein, polysaccharides, carotene, and minerals such as iron, zinc, and selenium. Marine fungi and algae, like seaweed and kelp, are also rich in iodine. Dark-colored vegetables: a perfect combination of color, aroma, flavor, and nutrition.
Dark-colored vegetables refer to deep green, red, orange-red, and purple-red vegetables, which are rich in carotene, especially β-carotene, and are the main source of vitamin A for Chinese residents. In addition, dark-colored vegetables contain many other pigments such as chlorophyll, lutein, lycopene, and anthocyanins, as well as aromatic substances that give vegetables their special colors, flavors, and aromas. These can stimulate appetite and exhibit certain special physiological activities.
Common dark green vegetables: spinach, rape, winter cress, celery leaves, water spinach (onion green), lettuce leaves, mustard greens, broccoli, watercress, scallions, crown daisy, chives, radish greens, etc.
Common red and orange-red vegetables: tomatoes, carrots, pumpkins, red peppers, etc.
Common purple-red vegetables: red amaranth, red cabbage, Houttuynia cordata, etc.