Micronutrients include vitamins, macro minerals, trace minerals, organic acids and many many more, some of which we do not understand. They are called micronutrients because we only need these nutrients in small amount. These nutrients play important roles in our body. Some are antioxidants that fights oxidation damage. Some are part of important chemical processes. Compared to the macronutrients, micronutrients are less understood given that there are so many of them and they exist in small quantities.
Although we only need small amount of micronutrients, there is a wide spread deficiency of them. The reason is there are so many different micronutrients. We need to eat diversely to cover all of them. Micronutrients exist more densely in fruits and vegetables so people who don’t eat wide range of them can develop micronutrient deficiency.
Another reason is the use of fertilizer and bad agricultural practice have caused massive soil erosion. Less healthy soil hold less micronutrients. Initially plants will survive with some micronutrient deficiency. Farmers usually do not replenish micronutrients until the problem is apparent. So even people eat enough fruits and vegetables, if the quality is bad, can have deficiency in micronutrients.
For example, suppose you eat a home-planted organic tomato and a store bought conventional tomato. Obviously the home-planted organic tomato is going to taste much better and the store bought conventional tomato is going to taste much bland. There must be something missing or different in the store bought tomato. However, now our society is assuming them to be quite similar.
Under a microscope or chemical analysis, the two tomatoes may be similar, but traditionally, Chinese have always assume that if things taste different, they must have different effect on the body. In fact, many connoisseurs of tea, coffee and wine can discern the origin of the food just on taste. It is an incredible feat that we cannot replicate with machines. It shows that human body is the most delicate machine on earth and there is a lot about nature, food and medicine we do not yet understand. So we must revere nature and try not to mess with it.