The contents of protein, carbohydrate and fat are low in leaf vegetables, less than 2%, 5% and 0.5% on average, respectively.
Leaf vegetables also contain folic acid, choline, calcium and phosphorus, but the high content of calcium in amaranth, spinach and bamboo shoots is combined with oxalic acid, making it difficult for the body to absorb. The high content of oxalic acid in vegetables can not only interfere with the absorption of calcium but also disturb the calcification of bones after soluble oxalates in food are absorbed by the body.
Therefore, infants, pregnant women and bone fracture patients should not take too many vegetables rich in oxalic acid.
Root and rhizome vegetables: Radishes, Chinese yams, lotus roots, potatoes, taros, sweet potatoes, garlic, greenonions, asparagus, lettuce and bamboo shoots belong to this group of vegetables containing different nutrients. The starch in potatoes, taros, lotus roots and sweet potatoes is as high as 15-30%, and it is 29.5% in sweet potatoes. The content of carotin in carrots is as high as 3.62 mg%. The contents of protein and fat in this group of vegetables are low, and theprotein in potatoes and taros is slightly higher (2%) than that of other root and rhizome vegetables.
Different from leaf vegetables, many root vegetables can be taken as staple foodstuffs, because they contain a great deal" of sugar. Although the content of vitamin C in radishes and asparagus is not rich, the uncooked dishes of these vegetables can also supply lots of vitamin C because it is not destroyed in uncooked vegetables. According to pharmacological studies, the lignin in radishes can produce an anti-cancer effect. In addition, the potassium succinate in carrots can produce a hypotensive effect. The juice of fresh carrots is a health giving drink.