A large number of the nutrition needed by our body is derived from vegetables. For an adult, he should take in 200 to 500 grams of vegetables every day, so as to meet the basic needs of the body. In daily life, people tend to select vegetable according to its price and taste. In fact, it is not scientific. The major way to determine the nutritional value of the vegetable is how much essential nutrients it contains, for example, vitamins, iron, salt, cellulose and other necessary nutrition needed by the body.

After analyzing the nutrition constituents of various kinds of vegetables, scientists have found out that, the color of the vegetable is highly related with its nutrition. The vegetable with a dark color tend to has high nutritional value, and the light color indicates low nutritional value. The correct order is "green vegetables—red and yellow vegetables—colorless vegetable", with the nutritional value decreasing by the order.

Scientists also found that, in the same kind of vegetable, because of the different colors, the nutritional value will also be different for each specific vegetable. For example, the nutritional value of yellow carrot is much higher than the red carrot. Apart from a large number of carotene, yellow carrot also contains flavone, which can inhibit cancer, so it is plays an important role in the prevention of cancer.

What's more, scientists also point out that, the color differences in different parts of the same vegetable will result in different nutritional value. Take the shallot for example. The light green part of the shallot contains much higher nutritional value than the light blue part. Every 100 grams of light green contain 1750 international units of vitamin A, while the light blue part rarely contains any vitamin A. And the content of vitamin B1 and vitamin C in the light blue part is less than half amount of that in the light green part. What's more, the celery leave with a dark green color contain 6 times more carotene and 4 times more vitamin D than those in the celery leave with a light color.

Each kind of vegetable contains different types and quantities of nutrients, but the nutritional need of human is multifaceted, so when you select the vegetables, besides paying attention to the color of the vegetable, you should also consider to mixing various kinds of vegetables together or eating them with some meat, so as to provide sufficient and balanced nutrition to the body.